如何实现触发器Spring-Data Repository的保存方法之前/之后

Question

I've got a big number of entities. For every entity I've got an interface that extends CrudRepository . Every entity is saved using *Repository.save(entity) method.

And I want to implement a logger like that:

• have a separate database for logs with two tables: log & logdata
• log table:
  • created
  • username
• logdata table:
  • log_id
  • fieldname
  • value (of string)
• when save or delete method runs, MyRepositoryTrigger should write a log message with all fields changed with field names and field values.

But how to write smth like that?

Answer 1

For trigger functionality you'll have to look at your DB but most likely it won't guarantee exclusivity of your CrudRepository DB activity since it's set upon creation/deletion/update of table/column.

If instead you want to imitate trigger functionality meaning something to fire without you having to set it up every single time before/after your CrudRepository#save()/delete() functionality then you are better off using Spring AOP functionality

@After("execution(* my.CrudRepository.save(..))")
public void log(JoinPoint point) {
    log.info(point.getSignature().getName() + " was called..");
}

You can find extensive Spring AOP programming documentation in the Spring Docs

Answer 2

It looks like you are trying to implement audit log for the changes. If you are using Spring Data JPA with Hibernate, I may recommend using Hibernate Envers that solves you everything. You add the maven dependency, then you add @Audited annotation on your entity (or on your interface), and envers will create an *_aud table for every entity you have audit on and add changelog automatically.

Storing user-id is a bit trickier, but you may find example here in the documentation for that as well .