Updating an Entity to the Database using JPA with Hibernate

Updating an Entity :

• Once an entity in the database, Student student = entintyManager.find(Student.class, 1L); this line will retrieve student entity where identifier value is 1.
• The above line makes the state of Student object “persistent”.
• Persistent state instances are always associated with persistence-context and transnational.
• If we are changing persistent State object values those are synchronized automatically with the database while committing the transaction.

Note:
To understand JPA entity life cycle completely see this tutorial JPA Entity lifecycle

Persistence transition or state change when EntityManager’s find() called :

Technologies Used in all of examples :

• JPA 2.1
• Hibernate 5.2.6
• MySql 8.0
• Maven 3
• Spring Tool Suite (STS) 3.9.8
• Java 1.8

Mapping Studen.java class

@Entity(name="STUDENT")
public class Student {
	
	@Id
	@GeneratedValue(strategy=GenerationType.AUTO, generator="native")
	@GenericGenerator(name = "native", strategy = "native")
	@Column(name = "ID")
	private Long studentId;
	
	@Column(name = "FNAME")
	private String firstName;
	
	@Column(name = "LNAME")
	private String lastName;
	
	@Column(name = "CONTACT_NO")
	private String contactNo;

       // setters and getters

Updating Entity Code :

Following example demonstrates updating column value of Student table when a Student record already exist in DB.

public static void main( String[] args )
    {
        EntityManagerFactory emf = null;
        EntityManager entityManager = null;
        EntityTransaction transaction = null;
        
        try{
            emf = Persistence.createEntityManagerFactory("jbd-pu");
            entityManager = emf.createEntityManager();
            transaction = entityManager.getTransaction();
            transaction.begin();
            
            /* When ever EntityManager's find() calls the state of Student instance will be "Persistent" */
            Student student = entityManager.find(Student.class, 2L);
            
            /*If we are changing persistent State object values,
             *  those are synchronized automatically with the database while committing the transaction.*/
            student.setFirstName("Peter");
            transaction.commit();
        }catch(Exception e){
            transaction.rollback();
        }finally{
            entityManager.close();
            emf.close();
        }
    }

Output :

INFO - HHH000397: Using ASTQueryTranslatorFactory
Hibernate: select student0_.ID as ID1_0_0_, student0_.CONTACT_NO as CONTACT_2_0_0_, student0_.FNAME as FNAME3_0_0_, student0_.LNAME as LNAME4_0_0_ from STUDENT student0_ where student0_.ID=?
Hibernate: update STUDENT set CONTACT_NO=?, FNAME=?, LNAME=? where ID=?
INFO - HHH000030: Cleaning up connection pool [jdbc:mysql://localhost:3306/jpa_JBD]

To update detached entities to the database, use merge method.

Download Application – JPA-Entity-Update.zip (10 KB)