Skip to main content

JPA Lifecycle Callback Events

Typical Entity Life-cycle

  • Persist   - Creating Entity for the first time.
  • Merge   - Updating detached Entity
  • Load     - Loading Entity from Database
  • Delete   - Deleting Entity from Database


JPA provides total of 6 Annotations for Life-Cycle Callback events.

  1. @PrePersist
  2. @PostPersist
  3. @PreUpdate
  4. @PostUpdate
  5. @PreRemove
  6. @PostLoad


Following two ways to utilize the above annotations.

Case 1: Defining inside Entity class

Any method can be annotated with one or all annotations, though they should follow these rules.


  1.  Method can have any name
  2.  No parameters
  3.  Return type of void
  4.  Method should not be final or static
  5.  No Checked exceptions should be thrown
  6.  Any annotation can be only used on one method


Example Code Snippet - 1

@Entity
public class Employee implements Serializable {
...

@PrePersist
@PostPersist
@PreUpdate
@PostUpdate
@PreRemove
@PostLoad
public void updateDate() {
    // this method will executed on all the lifecycle events.
}
}

Way 2 : Using Entity Listeners Classes
This is very nice way of using the annotations.

Example Code Snippet - 2


@EntityListeners({LastAccessDateListener.class})
public class Employee implements NamedEntity {
...
}

public class LastAccessDateListener {
@PrePersist
@PostPersist
@PreUpdate
@PostUpdate
@PreRemove
@PostLoad
public void updateDate(Employee e) {
  // this method is in totally separate class
}

}

LastAccessDateListener class doesn't have to be annotated or extend any other class.

Comments

Post a Comment

Popular posts from this blog

JPA 2 new feature @ElementCollection explained

@ElementCollection is new annotation introduced in JPA 2.0, This will help us get rid of One-Many and Many-One shitty syntax. Example 1: Stores list of Strings in an Entity @Entity public class Users implements Serializable {     private static final long serialVersionUID = 1L;     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Long id;     @ElementCollection     private List<String> certifications = new ArrayList <String> ();     public Long getId() {         return id;     }     public void setId(Long id) {         this.id = id;     }     public List <String> getCertifications() {         return certifications;     }     public void setCertifications(List <String> certifications) {         this.certifications = certifications;     } .. }         Users u = new Users();         u.getCertifications().add("Sun Certified Java Programmer");         em.persist(u); Generated Tables    Users    Co
21 comments
Read more

Validating CSV Files

What is CsvValidator ?   A Java framework which validates any CSV files something similar to XML validation using XSD. Why should I use this ?   You don't have to use this and in fact its easy to write something your own and also checkout its source code for reference. Why did I write this ?   Some of our projects integrate with third party application which exchanges information in CSV files so I thought of writing a generic validator which can be hooked in multiple projects or can be used by QA for integration testing. What is the license clause ?   GNU GPL v2 Are there any JUnit test cases for me checkout ?  Yes,  source How to integrate in my existing project ? Just add the Jar which can be downloaded from here  CsvValidator.jar  and you are good. Instantiate  CsvValidator c onstructor which takes these 3 arguements          // filename is the the file to be validated and here is a  sample         // list - defines all the fields in the above csv file ( a
7 comments
Read more

Reuse JPA Entities as DTO

Note : Major design advantages of JPA Entities are they can detached and used across tiers and networks and later can by merged. Checkout this new way of querying entities in JPA 2.0 String ql = " SELECT new prepclass2.Employee (e.firstname, e.lastname) FROM Employee e "; List<Employee> dtos = em.createQuery(ql).getResultList(); The above query loads all Employee entities but with subset of data i.e. firstname, lastname. Employee entity looks like this. @Entity @Table(name="emp") public class Employee implements Serializable {     private static final long serialVersionUID = 1L;     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Long id;     @Column     private String firstname;     @Column     private String lastname;     @Column     private String username;     @Column     private String street;     @Column     private String city;     @Column     private String state;     @Column     private String zipc
11 comments
Read more