Java Reference
In-Depth Information
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 headers 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 URI matrix parameters.
@javax.ws.rs.QueryParam
This annotation allows you to extract values from URI 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.
Usually, these annotations are used on the parameters of a JAX-RS resource method. When
the JAX-RS provider receives an HTTP request, it finds a Java method that will service this
request. If the Java method has parameters that are annotated with any of these injection an-
notations, it will extract information from the HTTP request and pass it as a parameter when
it invokes the method.
