Set IdClass for Compound Key : Primary Key « JPA « Java

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Java » JPA » Primary KeyScreenshots 
Set IdClass for Compound Key




File: Professor.java


import java.util.ArrayList;
import java.util.Collection;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;

@Entity
public class Professor {
    @Id private int id;

    private String name;

    @OneToMany(mappedBy="employee")
    private Collection<ProjectAssignment> assignments;

    public Professor() {
        assignments = new ArrayList<ProjectAssignment>();
    }
    
    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 Collection<ProjectAssignment> getAssignments() {
        return assignments;
    }

    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 Project createProject(String name, int id) {
    Project emp = new Project();
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);
    return emp;
  }
  
  
  public Professor createProfessor(String country, int id, String name) {
    Professor emp = new Professor();
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);

    return emp;
  }

  public void addProfessorProject(int id, int projId) {
    Professor emp = findProfessor(id);
    Project proj = em.find(Project.class, projId);
    ProjectAssignment assign = new ProjectAssignment(emp, proj);

    em.persist(assign);
    emp.getAssignments().add(assign);
    proj.getAssignments().add(assign);
  }

  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();
  }

  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.OneToMany;

@Entity
public class Project {
    @Id private int id;
    private String name;
    
    @OneToMany(mappedBy="project")
    private Collection<ProjectAssignment> assignments;

    public Project() {
        assignments = new ArrayList<ProjectAssignment>();
    }
    
    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<ProjectAssignment> getAssignments() {
        return assignments;
    }
    
    public String toString() {
        return getClass().getName().substring(getClass().getName().lastIndexOf('.')+1
                " no: " + getId() 
                ", name: " + getName();
    }
}


File: ProjectAssignment.java


import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@Table(name = "EMP_PROJECT")
@IdClass(ProjectAssignmentId.class)
public class ProjectAssignment {
  @Id
  @Column(name = "EMP_ID", insertable = false, updatable = false)
  private int empId;

  @Id
  @Column(name = "PROJECT_ID", insertable = false, updatable = false)
  private int projectId;

  @ManyToOne
  @JoinColumn(name = "EMP_ID")
  Professor employee;

  @ManyToOne
  @JoinColumn(name = "PROJECT_ID")
  Project project;


  public ProjectAssignment() {
  }

  public ProjectAssignment(Professor emp, Project proj) {
    this.empId = emp.getId();
    this.employee = emp;
    this.projectId = proj.getId();
    this.project = proj;
  }

  public int getEmpId() {
    return empId;
  }

  public Professor getProfessor() {
    return employee;
  }

  public int getProjectId() {
    return projectId;
  }

  public Project getProject() {
    return project;
  }

}


File: ProjectAssignmentId.java


import java.io.Serializable;

public class ProjectAssignmentId implements Serializable {
    private int empId;
    private int projectId;
    
    public ProjectAssignmentId() {}
    public ProjectAssignmentId(int empId, int projectId) {
      this.empId = empId;
      this.projectId = projectId;
    }
    
    public int getEmpId() {
        return empId;
    }
    
    public int getProjectId() {
        return projectId;
    }
    
    public boolean equals(Object o) { 
        return ((instanceof ProjectAssignmentId&& 
                empId == ((ProjectAssignmentId)o).getEmpId() &&
                projectId == ((ProjectAssignmentIdo).getProjectId());
    }

    public int hashCode() { 
        return empId + projectId; 
    }
}


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 sqlthrows Exception {
    st.executeUpdate(sql);
  }
  public void checkData(String sqlthrows 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[] athrows Exception {
    JPAUtil util = new JPAUtil();

    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
    EntityManager em = emf.createEntityManager();
    ProfessorService service = new ProfessorService(em);

    em.getTransaction().begin();

    service.createProject("proj"1);
    
    service.createProfessor("country"1"name");

    service.addProfessorProject(11);

    System.out.println("Professors:");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp + " with " + emp.getAssignments().size() " assignments");
    }

    System.out.println("Projects:");
    for (Project p : service.findAllProjects()) {
      System.out.print(p + " with " + p.getAssignments().size() " assignments");
    }

    util.checkData("select * from Project");

    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>

           
       
JPA-SetIdClass.zip( 5,337 k)
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