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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().commit();
em.close();
emf.close();
}
}
File: persistence.xml
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/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>
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JPA-SetJoinColumns.zip( 5,338 k)