Chapter 50. Getting and Using Context Information

Abstract

Context information includes detailed information about a resource's URI, the HTTP headers, and other details that are not readily available using the other injection annotations. Apache CXF provides special class that amalgamates the all possible context information into a single object.

50.1. Introduction to contexts

Context annotation

You specify that context information is to be injected into a field or a resource method parameter using the javax.ws.rs.core.Context annotation. Annotating a field or parameter of one of the context types will instruct the runtime to inject the appropriate context information into the annotated field or parameter.

Types of contexts

Table 50.1, “Context types” lists the types of context information that can be injected and the objects that support them.

Table 50.1. Context types

ObjectContext information
UriInfo The full request URI
HttpHeaders The HTTP message headers
Request Information that can be used to determine the best representation variant or to determine if a set of preconditions have been set
SecurityContext Information about the security of the requester including the authentication scheme in use, if the request channel is secure, and the user principle

Where context information can be used

Context information is available to the following parts of a JAX-RS application:
  • resource classes
  • resource methods
  • entity providers
  • exception mappers

Scope

All context information injected using the @Context annotation is specific to the current request. This is true in all cases including entity providers and exception mappers.

Adding contexts

The JAX-RS framework allows developers to extend the types of information that can be injected using the context mechanism. You add custom contexts by implementing a Context<T> object and registering it with the runtime.