Skip to main content

JPA Hibernate Lifecycle Callback Events Simple Explanation

Typical Entity Life-cycle

  • Persist   - Creating Entity for the first time.
  • Merge    - Saving 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


This is how we can use the above annotations.

Solution 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.
}
}

Solution 2 : Using Entity Listeners Classes
This is very nice way of using the annotations. Clean code and same rules from above applies.

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

jasmin pethani said…
Hi! i am java aspirant, and i want more tutorials on JPA2.0
if you have any tutorial e-book then just sent link to the link

jazz.pethani@gmail.com

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
Column --> ID
    Row             1

Users_CERTIFICATIONS

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 constructor 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 field has index, type, isOptional, rege…

ArrayList vs LinkedList vs HashSet Performance Comparision

ConclusionsInserting & Reading sequentially from Collection prefer LinkedList/ArrayListInserting & Reading/Deleting by Search/equals from Collection prefer HashSetInserting, ArrayList & LinkedList performs best while HashSet takes double the timeReading, HashSet performs best while ArrayList & LinkedList are marginally lessDeleting, HashSet performs 10 times better than ArrayList & ArrayList performs 4 times better than LinkedList. LinkedList is slow because of sequencial search Bottom line : unless you are not going to iterate using for(Integer i : list ) then prefer HashSet
Inserting/Reading/Deleting integer's from zero till countJDK7Collectionactioncounttime msArrayListInsert1000/1LinkedListInsert1000/1HashSetInsert1000/1ArrayListInsert100005LinkedListInsert100004HashSetInsert100007ArrayListInsert10000011LinkedListInsert10000011HashSetInsert10000021ArrayListGet/Read1000LinkedListGet/Read1000HashSetGet/Read1000ArrayListGet/Read100004LinkedListGet/Read100003Has…