[FIXED] Spring MVC PATCH method: partial updates

Issue

I have a project where I am using Spring MVC + Jackson to build a REST service. Let's say I have the following java entity

public class MyEntity {
    private Integer id;
    private boolean aBoolean;
    private String aVeryBigString;
    //getter & setters
}

Sometimes, I just want to update the boolean value, and I don't think that sending the whole object with its big string is a good idea just to update a simple boolean. So, I have considered using the PATCH HTTP method to only send the fields that need to be updated. So, I declare the following method in my controller:

@RequestMapping(method = RequestMethod.PATCH)
public void patch(@RequestBody MyVariable myVariable) {
    //calling a service to update the entity
}

The problem is: how do I know which fields need to be updated? For instance, if the client just wants to update the boolean, I will get an object with an empty "aVeryBigString". How am I supposed to know that the user just wants to update the boolean, but does not want to empty the string?

I have "solved" the problem by building custom URLs. For instance, the following URL: POST /myentities/1/aboolean/true will be mapped to a method that allows to only update the boolean. The problem with this solution is that it is not REST compliant. I don't want to be 100% REST compliant, but I do not feel comfortable with providing a custom URL to update each field (especially given that it causes problems when I want to update several fields).

Another solution would be to split "MyEntity" into multiple resources and just update these resources, but I feel like it does not make sense: "MyEntity" is a plain resource, it is not composed of other resources.

So, is there an elegant way of solving this problem?

Solution

You may change boolean to Boolean and assign null value for all fields that you don't want to update. The only one not null value will define you which field client want to update.

Answered By - mvb13