Use Entity Returned From Merge Operation : Update « JPA

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Java Tutorial » JPA » Update

22. 4. 1. Use Entity Returned From Merge Operation

File: Student.java


import javax.persistence.CascadeType;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.ManyToOne;



@Entity

public class Student {

    @Id

    private int id;

    private String name;

    





    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 String toString() {

        return "Student id: " + getId() + " name: " + getName();

    }

}

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 {

  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");

  static EntityManager em = emf.createEntityManager();



  public static void main(String[] a) throws Exception {

    em.getTransaction().begin();

    

    

    Student emp = new Student();

    emp.setId(1);

    emp.setName("name");

    em.persist(emp);



    if (em.find(Student.class, emp.getId()) == null) {

      throw new IllegalArgumentException("Unknown employee id: " + emp.getId());

    }

    Student managedEmp = em.merge(emp);

    managedEmp.setName("new Name");





    Query query = em.createQuery("SELECT e FROM Student e");

    List<Student> list = (List<Student>) query.getResultList();

    System.out.println(list);

    

    

    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>

Download: JPA-UseEntityReturnedFromMerge.zip( 5,288 k)

22. 4. Update
	22. 4. 1.	Use Entity Returned From Merge Operation
	22. 4. 2.	Update an Entity from find method
	22. 4. 3.	EJB QL Update With Condition

Use Entity Returned From Merge Operation : Update « JPA « Java Tutorial