Map Hierarchical Data : Inheritance « JPA « Java

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Java » JPA » InheritanceScreenshots 
Map Hierarchical Data



File: Professor.java

import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.Lob;
import javax.persistence.ManyToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.SecondaryTable;
import javax.persistence.SecondaryTables;

@Entity
@SecondaryTables( {
    @SecondaryTable(name = "COMPANY", pkJoinColumns = {
        @PrimaryKeyJoinColumn(name = "ID", referencedColumnName = "ID") })
        
})
public class Professor {
  private String country;

  @Id
  private int id;

  private String name;

  @ManyToOne
  @JoinColumns( {
      @JoinColumn(name = "MGR_ID", referencedColumnName = "ID", table = "COMPANY") })
  private Professor manager;

  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 Professor getManager() {
    return manager;
  }

  public void setManager(Professor manager) {
    this.manager = manager;
  }

  public String toString() {
    return "Professor id: " + getId() " name: " + getName() " country: " + getCountry();
  }
}


File: ProfessorId.java

import java.io.Serializable;

public class ProfessorId implements Serializable {
  private String country;

  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 ((instanceof ProfessorId&& country.equals(((ProfessorIdo).getCountry()) && id == ((ProfessorIdo)
        .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) {
    Professor emp = new Professor();
    emp.setCountry(country);
    emp.setId(id);
    emp.setName(name);
    em.persist(emp);

    return 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();
  }
}


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.createProfessor("country"1"name");
    System.out.println("Professors:");
    for (Professor emp : service.findAllProfessors()) {
      System.out.print(emp);
      System.out.print(emp.getManager());
    }

    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>




           
       
JPA-MapHierarchicalData.zip( 5,335 k)
Related examples in the same category
1. Single Table Inheritance
2. Using Mapped Super class
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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