Java Tutorial/JPA/Generated ID

Create Table From Table Generator

File: Student.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.TableGenerator;
@Entity
public class Student {
  @TableGenerator(name = "Address_Gen", table = "ID_GEN", pkColumnName = "GEN_NAME", valueColumnName = "GEN_VAL", pkColumnValue = "Addr_Gen", initialValue = 10000, allocationSize = 100)
  @Id
  @GeneratedValue(strategy = GenerationType.TABLE, generator = "Address_Gen")
  private int id;
  transient private String name;
  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 toString() {
    return "\n\nID:" + id + "\nName:" + name + "\n\n";
  }
}

Create Your Own Table For Table Generator

File: Student.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.TableGenerator;
@Entity
public class Student {
  @Id
  @TableGenerator(name = "EmpPkGen",
      table = "ID_GEN",
      pkColumnName = "GEN_NAME", 
      pkColumnValue = "Emp_Gen", 
      valueColumnName = "GEN_VAL", 
      initialValue = 0,
      allocationSize = 100
   )
  @GeneratedValue(strategy=GenerationType.TABLE)
/*create table id_gen (
    gen_name varchar(80),
    gen_val integer,
    constraint pk_id_gen
        primary key (gen_name)
);
*/
  private int id;
  transient private String name;

  
  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 toString() {
    return "\n\nID:" + id + "\nName:" + name + "\n\n";
  }
}

Generated Value Based On Sequence Generator

File: Student.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
@Entity
public class Student {
  @SequenceGenerator(name="Emp_Gen", sequenceName="Emp_Seq")
  @Id @GeneratedValue(generator="Emp_Gen")
  private int id;
  private String name;

  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 toString() {
    return "\n\nID:" + id + "\nName:" + name + "\n\n";
  }
}

Generate ID From a Table

File: Student.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.TableGenerator;
@Entity
public class Student {
  @TableGenerator(name = "Address_Gen", table = "ID_GEN", pkColumnName = "GEN_NAME", valueColumnName = "GEN_VAL", pkColumnValue = "Addr_Gen", initialValue = 10000, allocationSize = 100)
  @Id
  @GeneratedValue(strategy = GenerationType.TABLE, generator = "Address_Gen")
  private int id;
  transient private String name;
  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 toString() {
    return "\n\nID:" + id + "\nName:" + name + "\n\n";
  }
}

ID Generation Type: AUTO

File: Helper.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class Helper {
  public static void checkData() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");
    Statement st = conn.createStatement();
    ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
    while (mrs.next()) {
      String tableName = mrs.getString(3);
      System.out.println("\n\n\n\nTable Name: "+ tableName);
      ResultSet rs = st.executeQuery("select * from " + tableName);
      ResultSetMetaData metadata = rs.getMetaData();
      while (rs.next()) {
        System.out.println(" Row:");
        for (int i = 0; i < metadata.getColumnCount(); i++) {
          System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");
          System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");
          Object value = rs.getObject(i + 1);
          System.out.println("    Column Value: "+value+"\n");
        }
      }
    }
  }
}

ID Generation Type: IDENTITY

File: Main.java

import java.sql.Timestamp;
import java.util.List;
import java.util.UUID;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    
    
    Student student = new Student();
    student.setName("Joe");
  
    
    em.persist(student);
    em.flush();
    em.getTransaction().rumit();
    
    Query query = em.createQuery("SELECT e FROM Student e");
    List<Student> list = (List<Student>) query.getResultList();
    System.out.println(list);
    
    
    em.close();
    emf.close();
    
    Helper.checkData();
  }
}

ID Generation Type: SEQUENCE

File: Main.java

import java.sql.Timestamp;
import java.util.List;
import java.util.UUID;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    
    
    Student student = new Student();
    student.setName("Joe");
  
    
    em.persist(student);
    em.flush();
    em.getTransaction().rumit();
    
    Query query = em.createQuery("SELECT e FROM Student e");
    List<Student> list = (List<Student>) query.getResultList();
    System.out.println(list);
    
    
    em.close();
    emf.close();
    
    Helper.checkData();
  }
}

ID Generation Type: TABLE

File: Helper.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class Helper {
  public static void checkData() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");
    Statement st = conn.createStatement();
    ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
    while (mrs.next()) {
      String tableName = mrs.getString(3);
      System.out.println("\n\n\n\nTable Name: "+ tableName);
      ResultSet rs = st.executeQuery("select * from " + tableName);
      ResultSetMetaData metadata = rs.getMetaData();
      while (rs.next()) {
        System.out.println(" Row:");
        for (int i = 0; i < metadata.getColumnCount(); i++) {
          System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");
          System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");
          Object value = rs.getObject(i + 1);
          System.out.println("    Column Value: "+value+"\n");
        }
      }
    }
  }
}

JPA Create Sequence Table For You

File: Helper.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class Helper {
  public static void checkData() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");
    Statement st = conn.createStatement();
    ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
    while (mrs.next()) {
      String tableName = mrs.getString(3);
      System.out.println("\n\n\n\nTable Name: "+ tableName);
      ResultSet rs = st.executeQuery("select * from " + tableName);
      ResultSetMetaData metadata = rs.getMetaData();
      while (rs.next()) {
        System.out.println(" Row:");
        for (int i = 0; i < metadata.getColumnCount(); i++) {
          System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");
          System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");
          Object value = rs.getObject(i + 1);
          System.out.println("    Column Value: "+value+"\n");
        }
      }
    }
  }
}

Sequence Generator Name Init Value And Size

File: Customer.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.PostLoad;
import javax.persistence.PostPersist;
import javax.persistence.PostRemove;
import javax.persistence.PostUpdate;
import javax.persistence.PrePersist;
import javax.persistence.PreRemove;
import javax.persistence.PreUpdate;
import javax.persistence.SequenceGenerator;
@Entity
@SequenceGenerator(name = "SequenceIdGenerator", 
    sequenceName = "SEQ_ID_GEN", initialValue = 100, 
    allocationSize = 20)
public class Customer implements java.io.Serializable {
  @Id
  @GeneratedValue(generator = "SequenceIdGenerator")
  private int id;
  private String lastName;
  private String firstName;

  public int getId() {
    return id;
  }
  public void setId(int pk) {
    id = pk;
  }
  public String getLastName() {
    return lastName;
  }
  public void setLastName(String lastName) {
    this.lastName = lastName;
  }
  public String getFirstName() {
    return firstName;
  }
  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }
  @PrePersist
  public void prePersist() {
    System.out.println("@PrePersist");
  }
  @PostPersist
  public void postPersist() {
    System.out.println("@PostPersist");
  }
  @PostLoad
  public void postLoad() {
    System.out.println("@PostLoad");
  }
  @PreUpdate
  public void preUpdate() {
    System.out.println("@PreUpdate");
  }
  @PostUpdate
  public void postUpdate() {
    System.out.println("@PostUpdate");
  }
  @PreRemove
  public void preRemove() {
    System.out.println("@PreRemove");
  }
  @PostRemove
  public void postRemove() {
    System.out.println("@PostRemove");
  }
}

Use Sequence Generator

File: Student.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
@Entity
public class Student {
  @SequenceGenerator(name="Emp_Gen", sequenceName="Emp_Seq")
  @Id @GeneratedValue(generator="Emp_Gen")
  private int id;
  private String name;

  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 toString() {
    return "\n\nID:" + id + "\nName:" + name + "\n\n";
  }
}