Java/JPA/Join Columns
Содержание
Inversion Join Column
<source lang="java">
File: Professor.java
import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; @Entity public class Professor {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
private String name;
private long salary;
@ManyToMany
@JoinTable(name="EMP_PROJ",
joinColumns=@JoinColumn(name="EMP_ID"),
inverseJoinColumns=@JoinColumn(name="PROJ_ID"))
private Collection<Project> projects;
public Professor() {
projects = new ArrayList<Project>();
}
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 long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public void addProject(Project project) {
if (!getProjects().contains(project)) {
getProjects().add(project);
}
if (!project.getProfessors().contains(this)) {
project.getProfessors().add(this);
}
}
public Collection<Project> getProjects() {
return projects;
}
public String toString() {
return "Professor id: " + getId() + " name: " + getName() +
" with " + getProjects().size() + " projects";
}
}
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 Project createProject(String name) {
Project proj = new Project();
proj.setName(name);
em.persist(proj);
return proj;
}
public Collection<Project> findAllProjects() {
Query query = em.createQuery("SELECT p FROM Project p");
return (Collection<Project>) query.getResultList();
}
public Professor createProfessor(String name, long salary) {
Professor emp = new Professor();
emp.setName(name);
emp.setSalary(salary);
em.persist(emp);
return emp;
}
public Professor addProfessorProject(int empId, int projId) {
Professor emp = em.find(Professor.class, empId);
Project proj = em.find(Project.class, projId);
proj.addProfessor(emp);
return emp;
}
public Collection<Professor> findAllProfessors() {
Query query = em.createQuery("SELECT e FROM Professor e");
return (Collection<Professor>) query.getResultList();
}
}
File: Project.java
import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.ManyToMany; @Entity public class Project {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
protected int id;
protected String name;
@ManyToMany(mappedBy="projects")
private Collection<Professor> employees;
public Project() {
employees = new ArrayList<Professor>();
}
public int getId() {
return id;
}
public void setId(int projectNo) {
this.id = projectNo;
}
public String getName() {
return name;
}
public void setName(String projectName) {
this.name = projectName;
}
public Collection<Professor> getProfessors() {
return employees;
}
public void addProfessor(Professor employee) {
if (!getProfessors().contains(employee)) {
getProfessors().add(employee);
}
if (!employee.getProjects().contains(this)) {
employee.getProjects().add(this);
}
}
public String toString() {
return "Project id: " + getId() + ", name: " + getName() +
" with " + getProfessors().size() + " employees";
}
}
File: Main.java import java.util.Collection; 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 = service.createProfessor("empName",100);
Project proj = service.createProject("projName");
emp = service.addProfessorProject(emp.getId(),proj.getId());
Collection<Professor> emps = service.findAllProfessors();
if (emps.isEmpty()) {
System.out.println("No Professors found ");
} else {
System.out.println("Found Professors:");
for (Professor emp1 : emps) {
System.out.println(emp1);
}
}
Collection<Project> projs = service.findAllProjects();
if (projs.isEmpty()) {
System.out.println("No Projects found ");
} else {
System.out.println("Found Projects:");
for (Project proj1 : projs) {
System.out.println(proj1);
}
}
util.checkData("select * from Professor");
util.checkData("select * from Project");
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>
</source>
Join Two Entities With Parameter
<source lang="java">
File: Department.java
import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.OneToMany; @Entity public class Department {
@Id
private int id;
private String name;
@OneToMany(mappedBy="department")
private Collection<Professor> employees;
public Department() {
employees = new ArrayList<Professor>();
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public Collection<Professor> getProfessors() {
return employees;
}
public String toString() {
return "Department no: " + getId() +
", name: " + getName();
}
}
File: Professor.java
import java.util.ArrayList; import java.util.Collection; import java.util.Date; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.ManyToMany; import javax.persistence.ManyToOne; import javax.persistence.OneToMany; import javax.persistence.Temporal; import javax.persistence.TemporalType; @Entity public class Professor {
@Id
private int id;
private String name;
private long salary;
@Temporal(TemporalType.DATE)
private Date startDate;
@ManyToOne
private Professor manager;
@OneToMany(mappedBy="manager")
private Collection<Professor> directs;
@ManyToOne
private Department department;
@ManyToMany
private Collection<Project> projects;
public Professor() {
projects = new ArrayList<Project>();
directs = new ArrayList<Professor>();
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public long getSalary() {
return salary;
}
public Date getStartDate() {
return startDate;
}
public Department getDepartment() {
return department;
}
public Collection<Professor> getDirects() {
return directs;
}
public Professor getManager() {
return manager;
}
public Collection<Project> getProjects() {
return projects;
}
public String toString() {
return "Professor " + getId() +
": name: " + getName() +
", salary: " + getSalary() +
", dept: " + ((getDepartment() == null) ? null : getDepartment().getName());
}
}
File: ProfessorService.java import java.util.Collection; import javax.persistence.EntityManager; import javax.persistence.NoResultException; public class ProfessorService {
protected EntityManager em;
public ProfessorService(EntityManager em) {
this.em = em;
}
public long queryEmpSalary(String deptName, String empName) {
String query = "SELECT e.salary " + "FROM Professor e " + "WHERE e.department.name = ""
+ deptName + "" AND " + " e.name = "" + empName + """;
try {
return (Long) em.createQuery(query).getSingleResult();
} catch (NoResultException e) {
return 0;
}
}
public long queryEmpSalaryUsingParams(String deptName, String empName) {
try {
return (Long) em.createQuery(
"SELECT e.salary " + "FROM Professor e " + "WHERE e.department.name = :deptName AND "
+ " e.name = :empName ").setParameter("deptName", deptName).setParameter("empName",
empName).getSingleResult();
} catch (NoResultException e) {
return 0;
}
}
}
File: Project.java
import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.ManyToMany; @Entity public class Project {
@Id
protected int id;
protected String name;
@ManyToMany(mappedBy="projects")
private Collection<Professor> employees;
public Project() {
employees = new ArrayList<Professor>();
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public Collection<Professor> getProfessors() {
return employees;
}
public String toString() {
return "Project id: " + getId() + ", name: " + getName();
}
}
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 java.util.Collection; 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();
long l = service.queryEmpSalary("deptName", "empName");
long q = service.queryEmpSalaryUsingParams("deptName", "empName");
util.checkData("select * from Professor");
util.checkData("select * from Department");
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>
</source>
Mark Joined Column As Nullable
<source lang="java">
File: Address.java import javax.persistence.Entity; import javax.persistence.Id; @Entity public class Address {
@Id
private int id;
private String street;
private String city;
private String state;
private String zip;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getStreet() {
return street;
}
public void setStreet(String address) {
this.street = address;
}
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 getZip() {
return zip;
}
public void setZip(String zip) {
this.zip = zip;
}
public String toString() {
return "Address id: " + getId() +
", street: " + getStreet() +
", city: " + getCity() +
", state: " + getState() +
", zip: " + getZip();
}
}
File: Professor.java
import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; @Entity public class Professor {
@Id private int id;
@Column(nullable=false)
private String name;
private long salary;
@ManyToOne
@JoinColumn(nullable=false)
private Address address;
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 long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
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 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.findAllProfessors();
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>
</source>
Primary Key Column as Joined Column
<source lang="java">
File: ParkingSpace.java
import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.OneToOne; import javax.persistence.PrimaryKeyJoinColumn; import javax.persistence.Table; @Entity public class ParkingSpace {
@Id
private int id;
private int lot;
private String location;
@OneToOne
@PrimaryKeyJoinColumn
private Professor employee;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getLot() {
return lot;
}
public void setLot(int lot) {
this.lot = lot;
}
public String getLocation() {
return location;
}
public void setLocation(String deptName) {
this.location = deptName;
}
public Professor getProfessor() {
return employee;
}
public void setProfessor(Professor employee) {
this.employee = employee;
}
public String toString() {
return "ParkingSpace id: " + getId() + " lot: " + getLot() +
", location: " + getLocation();
}
}
File: Professor.java
import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.OneToOne; @Entity public class Professor {
@Id
private int id;
private String name;
private long salary;
@OneToOne(mappedBy="employee")
private ParkingSpace parkingSpace;
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 long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public ParkingSpace getParkingSpace() {
return parkingSpace;
}
public void setParkingSpace(ParkingSpace parkingSpace) {
this.parkingSpace = parkingSpace;
}
public String toString() {
return "Professor id: " + getId() + " name: " + getName() +
" with " + getParkingSpace();
}
}
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, long salary) {
Professor emp = new Professor();
emp.setId(id);
emp.setName(name);
emp.setSalary(salary);
em.persist(emp);
return emp;
}
public Collection<Professor> findAllProfessors() {
Query query = em.createQuery("SELECT e FROM Professor e");
return (Collection<Professor>) query.getResultList();
}
public ParkingSpace createParkingSpace(Professor emp, int lot, String location) {
ParkingSpace space = new ParkingSpace();
space.setId(emp.getId());
space.setLot(lot);
space.setLocation(location);
emp.setParkingSpace(space);
space.setProfessor(emp);
em.persist(space);
return space;
}
public Collection<ParkingSpace> findAllParkingSpaces() {
Query query = em.createQuery("SELECT p FROM ParkingSpace p");
return (Collection<ParkingSpace>) 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 java.util.Collection; 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 = service.createProfessor(1, "empName", 100L);
service.createParkingSpace(emp, 1, "location");
System.out.println("Created " + emp);
Collection<Professor> emps = service.findAllProfessors();
if (emps.isEmpty()) {
System.out.println("No Professors found ");
} else {
System.out.println("Found Professors:");
for (Professor emp1 : emps) {
System.out.println(emp1);
}
}
Collection<ParkingSpace> pSpaces = service.findAllParkingSpaces();
if (pSpaces.isEmpty()) {
System.out.println("No ParkingSpaces found ");
} else {
System.out.println("Found ParkingSpaces:");
for (ParkingSpace pSpace : pSpaces) {
System.out.println(pSpace);
}
}
util.checkData("select * from Professor");
util.checkData("select * from ParkingSpace");
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>
</source>
Set Referenced Column Inverse Join Column
<source lang="java">
File: Professor.java
import java.util.ArrayList; import java.util.Collection; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.IdClass; import javax.persistence.JoinColumn; import javax.persistence.JoinColumns; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; import javax.persistence.ManyToOne; import javax.persistence.OneToMany; @Entity @IdClass(ProfessorId.class) public class Professor {
@Id private String country;
@Id
@Column(name="EMP_ID")
private int id;
private String name;
private long salary;
@ManyToOne
@JoinColumns({
@JoinColumn(name="MGR_COUNTRY", referencedColumnName="COUNTRY"),
@JoinColumn(name="MGR_ID", referencedColumnName="EMP_ID")
})
private Professor manager;
@OneToMany(mappedBy="manager")
private Collection<Professor> directs;
@ManyToMany
@JoinTable(
name="EMP_PROJECT",
joinColumns={
@JoinColumn(name="EMP_COUNTRY", referencedColumnName="COUNTRY"),
@JoinColumn(name="EMP_ID", referencedColumnName="EMP_ID")},
inverseJoinColumns=@JoinColumn(name="PROJECT_ID"))
private Collection<Project> projects;
public Professor() {
directs = new ArrayList<Professor>();
projects = new ArrayList<Project>();
}
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 long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public Collection<Professor> getDirects() {
return directs;
}
public Professor getManager() {
return manager;
}
public void setManager(Professor manager) {
this.manager = manager;
}
public Collection<Project> getProjects() {
return projects;
}
public String toString() {
return "Professor id: " + getId() + " name: " + getName() +
" country: " + getCountry();
}
}
File: ProfessorId.java import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Embeddable; @Embeddable public class ProfessorId implements Serializable{
private String country;
@Column(name = "EMP_ID")
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, long salary) {
Professor emp = new Professor();
emp.setCountry(country);
emp.setId(id);
emp.setName(name);
emp.setSalary(salary);
em.persist(emp);
return emp;
}
public void createProject(String projName) {
Project proj = new Project();
proj.setName(projName);
em.persist(proj);
}
public void setProfessorManager(String country, int id, String mgrCountry, int mgrId) {
Professor emp = findProfessor(country, id);
Professor mgr = findProfessor(mgrCountry, mgrId);
emp.setManager(mgr);
mgr.getDirects().add(emp);
}
public void addProfessorProject(String country, int id, int projId) {
Professor emp = findProfessor(country, id);
Project proj = em.find(Project.class, projId);
emp.getProjects().add(proj);
proj.getProfessors().add(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();
}
public Collection<Project> findAllProjects() {
Query query = em.createQuery("SELECT p FROM Project p");
return (Collection<Project>) query.getResultList();
}
}
File: Project.java import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.ManyToMany; @Entity public class Project {
@Id
protected int id;
protected String name;
@ManyToMany(mappedBy = "projects")
protected Collection<Professor> employees = new ArrayList<Professor>();
public int getId() {
return id;
}
public void setId(int projectNo) {
this.id = projectNo;
}
public String getName() {
return name;
}
public void setName(String projectName) {
this.name = projectName;
}
public Collection<Professor> getProfessors() {
return employees;
}
public void addProfessor(Professor employee) {
if (!getProfessors().contains(employee)) {
getProfessors().add(employee);
}
if (!employee.getProjects().contains(this)) {
employee.getProjects().add(this);
}
}
public String toString() {
return getClass().getName().substring(getClass().getName().lastIndexOf(".") + 1) + " no: "
+ getId() + ", name: " + getName();
}
}
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", 100);
service.createProfessor("mgrcountry", 2, "mgrName", 100);
service.createProject("proj");
service.addProfessorProject("empCountry2", 1, 1);
service.setProfessorManager("Country", 1, "mgrCountry", 1);
System.out.println("Professors:");
for (Professor emp : service.findAllProfessors()) {
System.out.println(emp + " " + emp.getProjects().size());
System.out.println(emp + " " + emp.getManager());
}
System.out.println("Projects:");
for (Project p : service.findAllProjects()) {
System.out.print(p + " " + p.getProfessors().size());
}
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>
</source>
