Map One Field To Secondary Table : Secondary Table « JPA « Java Tutorial

1. Java Tutorial
2. JPA
3. Secondary Table

File: Employee.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="EMP_LOB", pkJoinColumns={
      @PrimaryKeyJoinColumn(name="ID", referencedColumnName="EMP_ID")})
})
public class Employee {

    @Id
    @Column(name="EMP_ID")
    private int id;
    private String name;

    @Basic(fetch=FetchType.LAZY)
    @Lob
    @Column(table="EMP_LOB")
    private byte[] photo;
    
    @Basic(fetch=FetchType.LAZY)
    @Lob
    @Column(table="EMP_LOB")
    private char[] comments;


    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 char[] getComments() {
        return comments;
    }

    public void setComments(char[] comments) {
        this.comments = comments;
    }

    public byte[] getPhoto() {
        return photo;
    }

    public void setPhoto(byte[] photo) {
        this.photo = photo;
    }

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

File: Address.java

import javax.persistence.Column;
import javax.persistence.Embeddable;

@Embeddable
public class Address {
    private String street; 
    private String city; 
    private String state;
    @Column(name="ZIP_CODE")
    private String zip;

    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 street: " + getStreet() +
               ", city: " + getCity() +
               ", state: " + getState() +
               ", zip: " + getZip();
    }

}

File: Helper.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;

public class Helper {
  public static void checkData() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");
    Statement st = conn.createStatement();

    ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
    while (mrs.next()) {
      String tableName = mrs.getString(3);
      System.out.println("\n\n\n\nTable Name: "+ tableName);

      ResultSet rs = st.executeQuery("select * from " + tableName);
      ResultSetMetaData metadata = rs.getMetaData();
      while (rs.next()) {
        System.out.println(" Row:");
        for (int i = 0; i < metadata.getColumnCount(); i++) {
          System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");
          System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");
          Object value = rs.getObject(i + 1);
          System.out.println("    Column Value: "+value+"\n");
        }
      }
    }
  }
}

File: Main.java

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");

  static EntityManager em = emf.createEntityManager();

  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();





    em.getTransaction().commit();
    em.close();
    emf.close();

    Helper.checkData();
  }
}

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>

22.17.Secondary Table
	22.17.1.	Secondary Table With Primary Key
	22.17.2.	Secondary Table With Many To One Relationship
	22.17.3.	Secondary Table With Compound Key
	22.17.4.	One Entity With Two Secondary Tables
	22.17.5.	Map One Field To Secondary Table
	22.17.6.	Map One Entity To More Than One Table