JPA Update Query Example

So far we have discussed the basics of Java persistence API. We discussed the history , the various concepts etc. In the just previous chapter we discussed about the insert and fetch operations with relational database using JPA.We used the slect query in JPA Query Language(JPQL) to fetch the contents from database. In this chapter we are looking into the JPQL Update query.

Update can be either a)Selective Update , or b) Update All

In this chapter we are discussing a selective update example. Selective update needs WHERE clause to select a particular row from the table.

We are using the same set of data we inserted to the database earlier. The project and its setup are same as explained in the previous chapter.There we inserted one Student object into the database table. In this chapter we are just updating the existing record. The entity class and the persistence.xml are same . The database configuration and all other required things were explained in the previous chapter.

Student.java – Entity class

import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table;


@Entity(name = "Student")

@Table(name="student")

public class Student implements Serializable {
    /**

     *

     */

    private static final long serialVersionUID = 1L;

    @Id

    @GeneratedValue(strategy = GenerationType.AUTO)

    private int id;

    private String name;

    private String level;
    public Student() {
    }
    public int getId() {

        return id;

    }
    public void setId(int id) {

        this.id = id;

    }
    public String getName() {

        return name;

    }
    @Column(name = "name")

    public void setName(String name) {

        this.name = name;

    }
    public String getLevel() {

        return level;

    }
    @Column(name = "level")

    public void setLevel(String level) {

        this.level = level;

    }
    public String toString(){

        return "ID = "+getId() + " ; Name : = "+getName() +" ; Level : = "+getLevel();

    }

}

persistence.xml

org.apache.openjpa.persistence.PersistenceProviderImpl com.jpa.entity.Student

Now let us see the main class.

UpdateSample.java

import java.util.Iterator; import java.util.List; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.EntityTransaction; import javax.persistence.Persistence; import javax.persistence.Query;


import com.jpa.entity.Student;
public class UpdateSample {
    public UpdateSample() {
    }
    public void readDetails() {

        EntityManagerFactory entityManagerFactory = Persistence

                .createEntityManagerFactory("OpenJPASample");

        EntityManager entityManager = entityManagerFactory

                .createEntityManager();

        if (null != entityManager) {

            EntityTransaction readTransaction = entityManager.getTransaction();

            readTransaction.begin();

            Query query = entityManager

                    .createQuery("select student FROM Student student");

            List list = query.getResultList();

            Iterator iterator = list.iterator();

            while (iterator.hasNext()) {

                Student student = (Student) iterator.next();

                System.out.println("Student Details : " + student);

            }

            readTransaction.commit();

        }

    }
    public void updateRecord() {

        EntityManagerFactory entityManagerFactory = Persistence

                .createEntityManagerFactory("OpenJPASample");

        EntityManager entityManager = entityManagerFactory

                .createEntityManager();

        if (null != entityManager) {

            EntityTransaction updateTransaction = entityManager

                    .getTransaction();

            updateTransaction.begin();

            Query query = entityManager

                    .createQuery("UPDATE Student student SET student.level = 'L' "

                            + "WHERE student.id= :id");

            query.setParameter("id", 1);

            int updateCount = query.executeUpdate();

            if (updateCount > 0) {

                System.out.println("Done...");

            }

            updateTransaction.commit();

        }

    }
    public static void main(String[] args) {

        UpdateSample sample = new UpdateSample();

        System.out.println("Before update..");

        sample.readDetails();

        sample.updateRecord();

        System.out.println("After Update");

        sample.readDetails();
    }

}

Update Query is not retrieving any data from database . It simply updates the database directly.It is a good practice to use a separate EntityManager for update query.