How to record entity changes

Question

Hi friends,
I am trying to implement feature which should record entity property changes. Basicaly I want to keep history when and what has changed in a separate table.
For example having a table similar to this and record all changes made to entities
Entity_ID, ENTITY, old_property_value, new_property_value.
Is it an easier way to achieve this using Persistence unit, rather than adding extra logic to each setters?
To better illustrate my problem here is simple example. Assume we have a simple entity class like
@Entity
public class UserEntity implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String fullName;
    public long getId() {
        return id;
    public void setId(long id) {
        this.id = id;
    public void setFullName(String fullName) {
        this.fullName = fullName;
    }Assume we call
myEntity.setFullName("New Name");And persisting changes should add record to separate table
ID ENTITY        OLD_VALUE    NEW_VALUE
1  UserEntity     Old Name    New NameI can simply add extra logic to setter or create a wrapper/controller classes but maybe there is an easier way to achieve this?
I am using glassfish application server.
Thank you for your help!

Answer 1

it depends how "efficient" you want the code to be. with some fairly straightforward JPA-only code, you could write a PostLoad hook method which recorded the current state of the entity in some sort of internal map (using the persistence annotations so that the code was not entity specific). then you could write a PrePersist hook method which takes the original state (as recorded by the PostLoad hook method) and compares it to the current state, and records any changes to your updates table. you could pile all of this into some common base class for all your persistent entities and you would be good to go. like a said, fairly straightforward to code, may not be super efficient at runtime.
probably the most efficient way to do this would be to use some sort of aspect oriented programming/byte code manipulation to automagically annotate all the setter methods to record updates in realtime to an internal updates map. then, a similar PrePersist hook can just use this updates map to record the updates to the appropriate table. again, you can most of this in a common base object type and then manipulate the byte code at some point to insert the setter hooks. a variation on this technique, if you didn't want to go the aspect oriented route, would be to manually insert the setter hook code into every setter method. pain in the butt to maintain, but sticks to builtin JPA functionality.