Spring Partial Update Object Data Binding

Question

We are trying to implement a special partial update function in Spring 3.2. We are using Spring for the backend and have a simple Javascript frontend. I\'ve not been able to

Answer 1

The main problem lies in your following code:

@RequestMapping(value = "/{id}", method = RequestMethod.POST )
public @ResponseBody ResponseEntity<User> update(@RequestBody User updateUser) {
    dbUser = userRepository.findOne(updateUser.getId());
    customObjectMerger(updateUser, dbUser);
    userRepository.saveAndFlush(updateUuser);
    ...
}

In the above functions, you call some of your private functions & classes (userRepository, customObjectMerger, ...), but give no explanation how it works or how those functions look like. So I can only guess:

CustomObjectMerger merges this updateUser with the corresponding dbUser from the database, updating the only fields included in updateUser.

Here we don't know what happened in CustomObjectMerger (that's your function, and you don't show it). But from what you describe, I can make a guess: you copy all the properties from updateUser to your object at database. This is absolutely a wrong way, since when Spring map the object, it will fill all the data. And you only want to update some specific properties.

There are 2 options in your case:

1) Sending all the properties (including the unchanged properties) to the server. This may cost a little more bandwidth, but you still keep your way

2) You should set some special values as the default value for the User object (for example, id = -1, age = -1...). Then in customObjectMerger you just set the value that is not -1.

If you feel the 2 above solutions aren't satisfied, consider parsing the json request yourself, and don't bother with Spring object mapping mechanism. Sometimes it just confuse a lot.

Answer 2

Partial updates can be solved by using @SessionAttributes functionality, which are made to do what you did yourself with the customObjectMerger.

Look at my answer here, especially the edits, to get you started:

https://stackoverflow.com/a/14702971/272180