Implementing PATCH support in JAX-RS resources

When a client changes only one part of the resource, you can optimize the entire update process by allowing the client to send only the modified part to the server and thereby saving the bandwidth and server resources. RFC 5789 proposes a solution for this use case via a new HTTP method, PATCH. We have already covered the theoretical concepts behind the PATCH method in Chapter 8, RESTful API Design Guidelines, under the Implementing partial update section. In this section, we will see how to actually implement the PATCH method in your JAX-RS application.

Defining the @PATCH annotation

JAX-RS allows you to define annotations to represent any custom or non-standard HTTP methods by annotating them with javax.ws.rs.HttpMethod. We will use this feature to define the @PATCH annotation, which can be used later to designate resource class methods for responding to HTTP PATCH method calls. Following is an example:

import javax.ws.rs.HttpMethod;
import...