Using Mapped Super class : Inheritance « JPA « Java

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Java » JPA » Inheritance 




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 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();

    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().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-UsingMappedSuperclass.zip( 5,336 k)
Related examples in the same category
1.Map Hierarchical Data
2.Single Table Inheritance
3.Set Inheritance And discriminator Column
4.Set Discriminator Value
5.Set Discriminator Column: Discriminator Type INTEGER
6.Map One POJO To Multiple Tables
7.Map Each Class In Hierarchy To Its Own Table
8.Many To One Mapping In Mapped Super class
9.Lifecycle CallBack Exclude Superclass Listeners
10.Lifecycle CallBack: Add Listener To Subclass
11.Inheritance Type TABLE_PER_CLASS
12.Inheritance Type JOINED
13.Change Inheritance Type In Hierarchy
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