CHAPTER 5 JAX-RS Injection A lot of JAX-RS is pulling information from an HTTP request and injecting it into a Java method. You may be interested in a fragment of the incoming URI. You might be interested in a URI query string value. The client might be sending critical HTTP head- ers or cookie values that your service needs to process the request. JAX-RS lets you grab this information à la carte, as you need it, through a set of injection annotations and APIs. The Basics There are a lot of different things JAX-RS annotations can inject. Here is a list of those provided by the specification: @javax.ws.rs.PathParam This annotation allows you to extract values from URI template parameters. @javax.ws.rs.MatrixParam This annotation allows you to extract values from a URI's matrix parameters. @javax.ws.rs.QueryParam This annotation allows you to extract values from a URI's query parameters. @javax.ws.rs.FormParam This annotation allows you to extract values from posted form data. @javax.ws.rs.HeaderParam This annotation allows you to extract values from HTTP request headers. @javax.ws.rs.CookieParam This annotation allows you to extract values from HTTP cookies set by the client. @javax.ws.rs.core.Context This class is the all-purpose injection annotation. It allows you to inject various helper and informational objects that are provided by the JAX-RS API. 55