Java/JPA/Inheritance

Change Inheritance Type In Hierarchy

File: BadProfessor.java

import javax.persistence.Column;
import javax.persistence.Entity;
@Entity 
public class BadProfessor extends CompanyProfessor {
    private long salary;
    @Column(name="PENSION")
    private long pensionContribution;
    
    public long getPensionContribution() {
        return pensionContribution;
    }
    
    public void setPensionContribution(long pension) {
        this.pensionContribution = pension;
    }
    
    public long getSalary() {
        return salary;
    }
    
    public void setSalary(long salary) {
        this.salary = salary;
    }
    public String toString() {
        return "FullTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: CompanyProfessor.java

import javax.persistence.Entity;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
@Entity
@Table(name="COMPANY_EMP")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public abstract class CompanyProfessor extends Professor {
    private int vacation;

    public int getVacation() {
        return vacation;
    }
    public void setVacation(int vacation) {
        this.vacation = vacation;
    }
}

File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name="EMP")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;

    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    BadProfessor emp2 = new BadProfessor();
    emp2.setId(2);
    emp2.setName("bad");
    
    service.createProfessor(emp2);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Inheritance Type JOINED

File: BadProfessor.java

import javax.persistence.Column;
import javax.persistence.Entity;
@Entity 
public class BadProfessor extends CompanyProfessor {
    private long salary;
    @Column(name="PENSION")
    private long pensionContribution;
    
    public long getPensionContribution() {
        return pensionContribution;
    }
    
    public void setPensionContribution(long pension) {
        this.pensionContribution = pension;
    }
    
    public long getSalary() {
        return salary;
    }
    
    public void setSalary(long salary) {
        this.salary = salary;
    }
    public String toString() {
        return "FullTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: CompanyProfessor.java

import javax.persistence.Entity;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
@Entity
@Table(name="COMPANY_EMP")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public abstract class CompanyProfessor extends Professor {
    private int vacation;

    public int getVacation() {
        return vacation;
    }
    public void setVacation(int vacation) {
        this.vacation = vacation;
    }
}

File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name="EMP")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;

    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    BadProfessor emp2 = new BadProfessor();
    emp2.setId(2);
    emp2.setName("bad");
    
    service.createProfessor(emp2);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Inheritance Type TABLE_PER_CLASS

File: BadProfessor.java

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
@Entity
@Table(name="BAD_EMP")
@AttributeOverrides({
    @AttributeOverride(name="name", column=@Column(name="FULLNAME")),
    @AttributeOverride(name="startDate", column=@Column(name="SDATE"))
})
public class BadProfessor extends Professor {
    @Column(name="D_RATE")
    private int dailyRate;
    private int term;
    
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }
    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class Professor  {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    BadProfessor emp2 = new BadProfessor();
    emp2.setId(2);
    emp2.setName("bad");
    
    service.createProfessor(emp2);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from BAD_EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Lifecycle CallBack: Add Listener To Subclass

File: ContractProfessor.java

import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.ExcludeSuperclassListeners;
import javax.persistence.PrePersist;
import javax.persistence.Table;
@Entity
@Table(name="CONTRACT_EMP")
@DiscriminatorValue("1")
@ExcludeSuperclassListeners
@EntityListeners(ProfessorDebugListener.class)
public class ContractProfessor extends Professor {
    @Column(name="D_RATE")
    private int dailyRate;
    private int term;
    
    @PrePersist
    public void verifyTerm() { 
        System.out.println("ContractProfessor.verifyTerm called on employee: " + getId());
    }
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }
    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.PostLoad;
import javax.persistence.PostPersist;
import javax.persistence.PostUpdate;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;
@Entity
@Table(name="EMP")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="EMP_TYPE", discriminatorType=DiscriminatorType.INTEGER)
@EntityListeners(ProfessorDebugListener.class)
public abstract class Professor {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    @Transient private long syncTime;
    @PostPersist
    @PostUpdate
    @PostLoad 
    private void resetSyncTime() { 
        System.out.println("Professor.resetSyncTime called on employee: " + getId());
        syncTime = System.currentTimeMillis(); 
    }
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorDebugListener.java
import javax.persistence.PostPersist;
public class ProfessorDebugListener {
  @PostPersist
  public void auditNewHire(Professor emp) { 
      System.out.println(" called on employee: " + emp.getId());
  }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public Professor createProfessor(int id, String name) {
    Professor emp = new ContractProfessor();
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);
    return emp;
  }
  public void removeProfessor(int id) {
    Professor emp = findProfessor(id);
    if (emp != null) {
      em.remove(emp);
    }
  }
  public Professor changeProfessorName(int id, String newName) {
    Professor emp = findProfessor(id);
    if (emp != null) {
      emp.setName(newName);
    }
    return emp;
  }
  public Professor findProfessor(int id) {
    return em.find(Professor.class, id);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    service.createProfessor(1, "name");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
    }
    service.changeProfessorName(1, "newname");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
    }
    service.removeProfessor(1);
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
    }
    util.checkData("select * from CONTRACT_EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}



File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Lifecycle CallBack Exclude Superclass Listeners

File: ContractProfessor.java

import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.ExcludeSuperclassListeners;
import javax.persistence.PrePersist;
import javax.persistence.Table;
@Entity
@Table(name="CONTRACT_EMP")
@DiscriminatorValue("1")
@ExcludeSuperclassListeners
@EntityListeners(ProfessorDebugListener.class)
public class ContractProfessor extends Professor {
    @Column(name="D_RATE")
    private int dailyRate;
    private int term;
    
    @PrePersist
    public void verifyTerm() { 
        System.out.println("ContractProfessor.verifyTerm called on employee: " + getId());
    }
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }
    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.PostLoad;
import javax.persistence.PostPersist;
import javax.persistence.PostUpdate;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;
@Entity
@Table(name="EMP")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="EMP_TYPE", discriminatorType=DiscriminatorType.INTEGER)
@EntityListeners(ProfessorDebugListener.class)
public abstract class Professor {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    @Transient private long syncTime;
    @PostPersist
    @PostUpdate
    @PostLoad 
    private void resetSyncTime() { 
        System.out.println("Professor.resetSyncTime called on employee: " + getId());
        syncTime = System.currentTimeMillis(); 
    }
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorDebugListener.java
import javax.persistence.PostPersist;
public class ProfessorDebugListener {
  @PostPersist
  public void auditNewHire(Professor emp) { 
      System.out.println(" called on employee: " + emp.getId());
  }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public Professor createProfessor(int id, String name) {
    Professor emp = new ContractProfessor();
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);
    return emp;
  }
  public void removeProfessor(int id) {
    Professor emp = findProfessor(id);
    if (emp != null) {
      em.remove(emp);
    }
  }
  public Professor changeProfessorName(int id, String newName) {
    Professor emp = findProfessor(id);
    if (emp != null) {
      emp.setName(newName);
    }
    return emp;
  }
  public Professor findProfessor(int id) {
    return em.find(Professor.class, id);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    service.createProfessor(1, "name");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
    }
    service.changeProfessorName(1, "newname");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
    }
    service.removeProfessor(1);
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
    }
    util.checkData("select * from CONTRACT_EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Many To One Mapping In Mapped Super class

File: BadProfessor.java

import javax.persistence.AssociationOverride;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.JoinColumn;
import javax.persistence.Table;
@Entity
@Table(name="Bad_EMP")
@AssociationOverride(name="manager", 
                     joinColumns=@JoinColumn(name="MGR"))
public class BadProfessor extends CompanyProfessor {
    @Column(name="H_RATE")
    private float hourlyRate;
    public float getHourlyRate() {
        return hourlyRate;
    }
    public void setHourlyRate(float hourlyRate) {
        this.hourlyRate = hourlyRate;
    }
    public String toString() {
        return "PartTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: CompanyProfessor.java

import javax.persistence.ManyToOne;
import javax.persistence.MappedSuperclass;
@MappedSuperclass
public abstract class CompanyProfessor extends Professor {
    private int vacation;
    @ManyToOne
    private Professor manager;
    public int getVacation() {
        return vacation;
    }
    public void setVacation(int vacation) {
        this.vacation = vacation;
    }
    public Professor getManager() {
        return manager;
    }
    public void setManager(Professor manager) {
        this.manager = manager;
    }
}

File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class Professor  {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    BadProfessor emp2 = new BadProfessor();
    emp2.setId(2);
    emp2.setName("bad");
    
    service.createProfessor(emp2);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from BAD_EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Map Each Class In Hierarchy To Its Own Table

File: BadProfessor.java

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
@Entity
@Table(name="CONTRACT_EMP")
public class BadProfessor extends Professor {
    @Column(name="D_RATE") private int dailyRate;
    private int term;
    
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }
    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name="EMP")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;

    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    BadProfessor emp2 = new BadProfessor();
    emp2.setId(2);
    emp2.setName("bad");
    
    service.createProfessor(emp2);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}



File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Map Hierarchical Data

File: Professor.java
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.Lob;
import javax.persistence.ManyToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.SecondaryTable;
import javax.persistence.SecondaryTables;
@Entity
@SecondaryTables( {
    @SecondaryTable(name = "COMPANY", pkJoinColumns = {
        @PrimaryKeyJoinColumn(name = "ID", referencedColumnName = "ID") })
        
})
public class Professor {
  private String country;
  @Id
  private int id;
  private String name;
  @ManyToOne
  @JoinColumns( {
      @JoinColumn(name = "MGR_ID", referencedColumnName = "ID", table = "COMPANY") })
  private Professor manager;
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public String getCountry() {
    return country;
  }
  public void setCountry(String country) {
    this.country = country;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public Professor getManager() {
    return manager;
  }
  public void setManager(Professor manager) {
    this.manager = manager;
  }
  public String toString() {
    return "Professor id: " + getId() + " name: " + getName() + " country: " + getCountry();
  }
}

File: ProfessorId.java
import java.io.Serializable;
public class ProfessorId implements Serializable {
  private String country;
  private int id;
  public ProfessorId() {
  }
  public ProfessorId(String country, int id) {
    this.country = country;
    this.id = id;
  }
  public String getCountry() {
    return country;
  }
  public int getId() {
    return id;
  }
  public boolean equals(Object o) {
    return ((o instanceof ProfessorId) && country.equals(((ProfessorId) o).getCountry()) && id == ((ProfessorId) o)
        .getId());
  }
  public int hashCode() {
    return country.hashCode() + id;
  }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public Professor createProfessor(String country, int id, String name) {
    Professor emp = new Professor();
    emp.setCountry(country);
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);
    return emp;
  }
  public Professor findProfessor(String country, int id) {
    return em.find(Professor.class, new ProfessorId(country, id));
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    service.createProfessor("country", 1, "name");
    System.out.println("Professors:");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
      System.out.print(emp.getManager());
    }
    util.checkData("select * from Professor");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Map One POJO To Multiple Tables

File: Professor.java
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.SecondaryTable;
import javax.persistence.Table;
@Entity
@Table(name = "EMP")
@SecondaryTable(name = "EMP_ADDRESS", pkJoinColumns = @PrimaryKeyJoinColumn(name = "EMP_ID"))
public class Professor {
  @Id
  private int id;
  private String name;
  @Column(table = "EMP_ADDRESS")
  private String street;
  @Column(table = "EMP_ADDRESS")
  private String city;
  @Column(table = "EMP_ADDRESS")
  private String state;
  @Column(name = "ZIP_CODE", table = "EMP_ADDRESS")
  private String zip;
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public String getCity() {
    return city;
  }
  public void setCity(String city) {
    this.city = city;
  }
  public String getState() {
    return state;
  }
  public void setState(String state) {
    this.state = state;
  }
  public String getStreet() {
    return street;
  }
  public void setStreet(String street) {
    this.street = street;
  }
  public String getZip() {
    return zip;
  }
  public void setZip(String zip) {
    this.zip = zip;
  }
  public String toString() {
    return "Professor id: " + getId() + " name: " + getName();
  }
}

File: ProfessorService.java
import java.util.Collection;
import java.util.Date;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public Professor createProfessorAndAddress(int id, String name, 
      String street, String city, String state, String zip) {
  Professor emp = new Professor();
  emp.setId(id);
  emp.setName(name);
  emp.setStreet(street);
  emp.setCity(city);
  emp.setState(state);
  emp.setZip(zip);
  em.persist(emp);
  
  return emp;
}
public Collection<Professor> findAllProfessors() {
  Query query = em.createQuery("SELECT e FROM Professor e");
  return (Collection<Professor>) query.getResultList();
}
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    service.createProfessorAndAddress(1, "name",  "street", "city", "state", "zip");
    System.out.println("Professors and Addresses:");
    for (Professor emp : service.findAllProfessors()) {
      System.out.println(emp);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}



File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Set Discriminator Column: Discriminator Type INTEGER

File: AbstractProfessor.java

import javax.persistence.MappedSuperclass;
@MappedSuperclass
public abstract class AbstractProfessor extends Professor {
    private int vacation;
    public int getVacation() {
        return vacation;
    }
    public void setVacation(int vacation) {
        this.vacation = vacation;
    }
}

File: BadProfessor.java
import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.Table;
@Entity
@Table(name="Bad_EMP")
@DiscriminatorValue("3")
public class BadProfessor extends AbstractProfessor {
    @Column(name="H_RATE")
    private float hourlyRate = 1;
    public float getHourlyRate() {
        return hourlyRate;
    }
    public void setHourlyRate(float hourlyRate) {
        this.hourlyRate = hourlyRate;
    }
    public String toString() {
        return "PartTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: GoodProfessor.java
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.Table;
@Entity
@Table(name="Good_EMP")
@DiscriminatorValue("2")
public class GoodProfessor extends AbstractProfessor {
    private long salary = 1;
    private long pension = 1;
    
    public long getPension() {
        return pension;
    }
    
    public void setPension(long pension) {
        this.pension = pension;
    }
    
    public long getSalary() {
        return salary;
    }
    
    public void setSalary(long salary) {
        this.salary = salary;
    }
    public String toString() {
        return "FullTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name = "EMP")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "EMP_TYPE", discriminatorType = DiscriminatorType.INTEGER)
public abstract class Professor {
  @Id
  private int id;
  private String name;
  @Temporal(TemporalType.DATE)
  @Column(name = "S_DATE")
  private Date startDate;
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public Date getStartDate() {
    return startDate;
  }
  public void setStartDate(Date startDate) {
    this.startDate = startDate;
  }
  public String toString() {
    return "Professor id: " + getId() + " name: " + getName();
  }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    GoodProfessor emp = null;
    emp = new GoodProfessor();
    emp.setId(1);
    emp.setName("good");
    
    service.createProfessor(emp);
    
    BadProfessor emp2 = new BadProfessor();
    emp2.setId(2);
    emp2.setName("bad");
    
    service.createProfessor(emp2);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Set Discriminator Value

File: AbstractProfessor.java

import javax.persistence.MappedSuperclass;
@MappedSuperclass
public abstract class AbstractProfessor extends Professor {
    private int vacation;
    public int getVacation() {
        return vacation;
    }
    public void setVacation(int vacation) {
        this.vacation = vacation;
    }
}

File: BadProfessor.java

import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity(name="BadEmp")
@DiscriminatorValue("BadEmp")
public class BadProfessor extends AbstractProfessor {
    @Column(name="H_RATE")
    private float hourlyRate;
    public float getHourlyRate() {
        return hourlyRate;
    }
    public void setHourlyRate(float hourlyRate) {
        this.hourlyRate = hourlyRate;
    }
    public String toString() {
        return "PartTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: GoodProfessor.java

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity
@DiscriminatorValue("GoodEmp")
public class GoodProfessor extends AbstractProfessor {
    private long salary;
    private long pension;
    
    public long getPension() {
        return pension;
    }
    
    public void setPension(long pension) {
        this.pension = pension;
    }
    
    public long getSalary() {
        return salary;
    }
    
    public void setSalary(long salary) {
        this.salary = salary;
    }
    public String toString() {
        return "GoodProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity 
@Table(name="EMP")
@Inheritance
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor  {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    Professor emp = null;
    emp = new GoodProfessor();
    emp.setId(1);
    emp.setName("good");
    service.createProfessor(emp);
    
    emp = new BadProfessor();
    emp.setId(2);
    emp.setName("bad");
    service.createProfessor(emp);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Set Inheritance And discriminator Column

File: ContractProfessor.java

import javax.persistence.Column;
import javax.persistence.Entity;
@Entity
public class ContractProfessor extends Professor {
    @Column(name="D_RATE")
    private int dailyRate;
    private int term;
    
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }
    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity 
@Table(name="EMP")
@Inheritance
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor  {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    Professor emp = null;
    emp = new ContractProfessor();
    emp.setId(1);
    emp.setName("name");
    service.createProfessor(emp);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}



File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Single Table Inheritance

File: ContractProfessor.java

import javax.persistence.Column;
import javax.persistence.Entity;
@Entity
public class ContractProfessor extends Professor {
    @Column(name="D_RATE")
    private int dailyRate;
    private int term;
    
    public int getDailyRate() {
        return dailyRate;
    }
    
    public void setDailyRate(int dailyRate) {
        this.dailyRate = dailyRate;
    }
    
    public int getTerm() {
        return term;
    }
    
    public void setTerm(int term) {
        this.term = term;
    }
    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

File: Professor.java

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity 
@Table(name="EMP")
@Inheritance
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor  {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    Professor emp = null;
    emp = new ContractProfessor();
    emp.setId(1);
    emp.setName("name");
    service.createProfessor(emp);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>

Using Mapped Super class

File: Professor.java

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity 
@Table(name="EMP")
@Inheritance
@DiscriminatorColumn(name="EMP_TYPE")
public abstract class Professor  {
    @Id private int id;
    private String name;
    @Temporal(TemporalType.DATE)
    @Column(name="S_DATE")
    private Date startDate;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public Date getStartDate() {
        return startDate;
    }
    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

File: BadProfessor.java

import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity(name="BadEmp")
@DiscriminatorValue("BadEmp")
public class BadProfessor extends AbstractProfessor {
    @Column(name="H_RATE")
    private float hourlyRate;
    public float getHourlyRate() {
        return hourlyRate;
    }
    public void setHourlyRate(float hourlyRate) {
        this.hourlyRate = hourlyRate;
    }
    public String toString() {
        return "PartTimeProfessor id: " + getId() + " name: " + getName();
    }
}

File: GoodProfessor.java

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity
@DiscriminatorValue("GoodEmp")
public class GoodProfessor extends AbstractProfessor {
    private long salary;
    private long pension;
    
    public long getPension() {
        return pension;
    }
    
    public void setPension(long pension) {
        this.pension = pension;
    }
    
    public long getSalary() {
        return salary;
    }
    
    public void setSalary(long salary) {
        this.salary = salary;
    }
    public String toString() {
        return "GoodProfessor id: " + getId() + " name: " + getName();
    }
}

File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
import javax.persistence.Query;
public class ProfessorService {
  protected EntityManager em;
  public ProfessorService(EntityManager em) {
    this.em = em;
  }
  public void createProfessor(Professor emp) {
    em.persist(emp);
  }
  public Collection<Professor> findAllProfessors() {
    Query query = em.createQuery("SELECT e FROM Professor e");
    return (Collection<Professor>) query.getResultList();
  }
}

File: AbstractProfessor.java

import javax.persistence.MappedSuperclass;
@MappedSuperclass
public abstract class AbstractProfessor extends Professor {
    private int vacation;
    public int getVacation() {
        return vacation;
    }
    public void setVacation(int vacation) {
        this.vacation = vacation;
    }
}

File: JPAUtil.java
import java.io.Reader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class JPAUtil {
  Statement st;
  
  public JPAUtil() throws Exception{
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    Connection conn = DriverManager.getConnection(url, "sa", "");
    System.out.println("Got Connection.");
    st = conn.createStatement();
  }
  public void executeSQLCommand(String sql) throws Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sql) throws Exception {
    ResultSet rs = st.executeQuery(sql);
    ResultSetMetaData metadata = rs.getMetaData();
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
    }
    System.out.println("\n----------------------------------");
    while (rs.next()) {
      for (int i = 0; i < metadata.getColumnCount(); i++) {
        Object value = rs.getObject(i + 1);
        if (value == null) {
          System.out.print("\t       ");
        } else {
          System.out.print("\t"+value.toString().trim());
        }
      }
      System.out.println("");
    }
  }
}

File: Main.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class Main {
  public static void main(String[] a) throws Exception {
    JPAUtil util = new JPAUtil();
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);
    em.getTransaction().begin();
    Professor emp = null;
    emp = new GoodProfessor();
    emp.setId(1);
    emp.setName("good");
    service.createProfessor(emp);
    
    emp = new BadProfessor();
    emp.setId(2);
    emp.setName("bad");
    service.createProfessor(emp);
    System.out.println("Professors: ");
    for (Professor emp1 : service.findAllProfessors()) {
      System.out.print(emp1);
    }
    util.checkData("select * from EMP");
    em.getTransaction().rumit();
    em.close();
    emf.close();
  }
}


File: persistence.xml
<persistence xmlns="http://java.sun.ru/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
      <property name="hibernate.connection.username" value="sa"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
    </properties>
  </persistence-unit>
</persistence>