Set ID By Yourself : Primary Key « JPA « Java Tutorial

1. Java Tutorial
2. JPA
3. Primary Key

File: Gender.java

public enum Gender {
  MALE, FEMALE
}

File: JPADAO.java

import java.util.Date;
import java.util.List;

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

public class JPADAO {
  EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  EntityManager em = emf.createEntityManager();

  public void create() {
    em.getTransaction().begin();
    
    
    Student student = new Student();
    student.setId(1);
    student.setName("Joe");
    student.setDateOfBirth(new Date());
    student.setGender(Gender.FEMALE);
    
    
    em.persist(student);
    em.flush();
    em.getTransaction().commit();
  }

  public void search() {
    Query q = em.createQuery("select m from Student m");
    for (Student m : (List<Student>) q.getResultList()) {
      System.out.println(m);
    }
  }

  public void close() {
    em.close();
    emf.close();
  }
}

File: Student.java

import java.util.Date;

import javax.persistence.Entity;
import javax.persistence.EnumType;
import javax.persistence.Enumerated;
import javax.persistence.Id;

@Entity
public class Student {
  @Id
  private long id = 0;

  private String name;

  private Date dateOfBirth = new Date();

  @Enumerated(EnumType.ORDINAL)
  private Gender gender;

  public Date getDateOfBirth() {
    return dateOfBirth;
  }

  public void setDateOfBirth(Date dateOfBirth) {
    this.dateOfBirth = dateOfBirth;
  }

  public long getId() {
    return id;
  }

  public void setId(long id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Gender getGender() {
    return gender;
  }

  public void setGender(Gender gender) {
    this.gender = gender;
  }

  public String toString() {
    return "\n\nID:" + id + "\nName:" + name + "\nBirthday:" + dateOfBirth + "\nGender:"
        + gender+"\n\n";
  }
}

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 java.util.List;

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

public class Main {
  public static void main(String[] a) throws Exception {
    JPADAO jpaDao = new JPADAO();
    
    jpaDao.create();
    jpaDao.search();
    
    
    jpaDao.close();
    Helper.checkData();
  }
}
/*

    [java] Table Name: STUDENT
    [java]  Row:
    [java]     Column Name: ID,
    [java]     Column Type: BIGINT:
    [java]     Column Value: 1

    [java]     Column Name: DATEOFBIRTH,
    [java]     Column Type: TIMESTAMP:
    [java]     Column Value: 2008-11-05 13:32:00.35

    [java]     Column Name: GENDER,
    [java]     Column Type: VARCHAR:
    [java]     Column Value: FEMALE

    [java]     Column Name: NAME,
    [java]     Column Type: VARCHAR:
    [java]     Column Value: Joe


*/

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>

22.19.Primary Key
	22.19.1.	Use UUID As Primary Key
	22.19.2.	Use Current Milisecond As ID
	22.19.3.	Set Primary Key Join Column For Entities In Hierarchy
	22.19.4.	Set ID By Yourself
	22.19.5.	Not Nullable ID
	22.19.6.	ID Entity With Hash Code And Equals
	22.19.7.	Id Containing Relationship
	22.19.8.	Embedded Compound Primary Key
	22.19.9.	Define Extra Class For Compound Key