[JPA] Use refresh to get updated data after database trigger

Today I met the issue about EntityManager cache issue.

Let's say that I have 2 tables comment and commant_like. I have a database trigger which increment the field like_count of comment when inserting one new comment_like record.

Below is the orignal code looks like:

In my expectation, the save call will make the database trigger to update the like_count in the comment, but it doesn't.

public void addLikeOnComment(...) {

    commentLikeDao.save(newEntity);
    
    Comment comment = commentDao.find(id);    
    
}

After digging into the code, I found the find has been called somewhere before addLikeComment. so the entity manager will use the cached version message.

public void doWork(...) {

    commentDao.find(id);

    addLikeOnComment(...);

}

The solution is simple. Use the entity manager refresh, to load data from database instead of the cached version

public void addLikeOnComment(...) {

    commentLikeDao.save(newEntity);
    
    Comment comment = commentDao.find(id); 
    commentDao.getEntityManager().refresh(comment)
    
}

-- EOF --