Java API for RESTful Web Services (JAX-RS) provides different
types of context to resource classes and providers. You can use context
objects to access request information such as discovering the HTTP
headers that are sent as part of the request. Context objects also
provide convenience methods for evaluating a request and building
an appropriate response.
About this task
Representational State Transfer (REST) application resources
might have a need to inspect some application context data upon invocation.
For example, a resource method that processes an HTTP GET query might
want to inspect the HTTP headers of the request for the Accept-Language HTTP
header so that the method can output a response in the language specified
by the request.
JAX-RS defines a simple way to retrieve this
data within the scope of the application resource. By declaring the
@Context annotation with the appropriate object as a parameter to
a resource method or as a field within the resource class, the data
that you want is injected into the resource. The JAX-RS implementation
populates the parameter or field with the contextual data, and the
resource method has access to all the contextual data it needs.
You
can use the following interface types that are injectable by the JAX-RS
runtime environment:
Interface types |
Description |
javax.ws.rs.core.UriInfo |
The UriInfo interface provides the complete URI specified
by the request. This interface can also inspect which resource(s)
matched the request URI. |
javax.ws.rs.core.Request |
The Request interface provides information about the request,
such as POST or GET. This interface can also evaluate preconditions
based on request entity tags. |
javax.ws.rs.core.HttpHeaders |
The HttpHeaders interface provides read-only access to all
HTTP headers. |
javax.ws.rs.core.SecurityContext |
The SecurityContext interface provides read-only information
about security, such as authentication scheme or security principal. |
javax.ws.rs.ext.Providers |
The Providers interface enables retrieval of ContextResolver,
ExceptionMapper, MessageBodyWriter, or MessageBodyReader implementations. |
In addition to the JAX-RS interface types, you
can inject web container types, such as javax.servlet.http.HttpServletRequest,
using the @Context annotation as described in the JAX-RS specification.
- Configure the development environment.
- Before you start developing JAX-RS applications, you
must set up your development environment by adding the JAX-RS libraries
on the classpath.
- Define the resources in JAX-RS web applications.
- Resources are the basic building block of a RESTful
service. Resources can contain static or dynamically updated data.
Examples of resources from an online book store application include
a book, an order from a store, and a collection of users. By identifying
the resources in your application, you can make the service more useful
and easier to develop.
- Configure the JAX-RS application.
You can
configure JAX-RS applications in multiple ways depending on your needs.
To take advantage of the Java™ Platform,
Enterprise Edition (Java EE)
6 functionality, you can use the annotation scanning capabilities.
By using annotation scanning, you can omit a JAX-RS javax.ws.rs.core.Application
subclass or have a minimally defined javax.ws.rs.core.Application
subclass. Alternatively, you can specify the IBM® JAX-RS servlet or filter if you want to use
the functionality available in the IBM JAX-RS
servlet and filter.
Using one of the JAX-RS Version 1.1 configuration
methods, you can omit a javax.ws.rs.core.Application subclass in your
application or have a javax.ws.rs.core.Application subclass that returns
an empty set of classes to inform the JAX-RS runtime environment to
find and use all the JAX-RS classes in the application. You might
want to use this method when you do not want to have to manually add
every relevant JAX-RS class to a javax.ws.rs.core.Application subclass
as you develop the application.
By specifying the specific IBM JAX-RS servlet and filter, you
can take advantage of and ensure specific IBM JAX-RS behavior. For example, using the IBM JAX-RS filter can be helpful
in developing a web application with a mix of JAX-RS resources and
JavaServer Pages (JSP) files with the same URL patterns.
Even
though there is a JAX-RS V1.1 configuration method that supports the
use of an optional web.xml file, if you want to specify security constraints
or roles, or you want to take advantage of other features enabled
using a web.xml file, you must specify the information in a web.xml
file.
Choose one of the following three methods to configure
your JAX-RS application:
- Configure
JAX-RS applications using JAX-RS 1.1 methods
Use this method
if you want to use the annotation scanning capabilities or to use
the JAX-RS 1.1 configuration methods. You can use the annotation
scanning capabilities to promote application portability, to minimize
the amount of configuration code, or to dynamically modify the application
without changes to the application code.
- Configure
the web.xml file for JAX-RS servlets
Use this method if you
want to specify features that are enabled using servlet initialization
parameters to change the behavior and ensure that you get the IBM JAX-RS servlet. When using
servlets, you can define a servlet path in the web.xml file that is
appended to the base URL.
- Configure
the web.xml file for JAX-RS filters
Use this method if you
want to use the filter when you have JSPs, other servlets and filters,
and JAX-RS resources with a mix of URL patterns. You can configure
the web.xml file to define filters that indicate the possible URLs
on which the filter can be invoked.
- Add context fields and parameters to obtain information
about requests. You can obtain information about requests
using HttpHeaders objects, UriInfo objects, Request objects, or SecurityContext
objects.
- Assemble JAX-RS web applications.
- After you develop the Java class
files for your JAX-RS web application and edit the web.xml file to
enable the JAX-RS servlet, you are ready to assemble the application.
Assemble the web application into a web application archive (WAR)
package. You can assemble the WAR package into an enterprise archive
(EAR) package if required.
- Deploy JAX-RS web applications.
- After you have assembled your JAX-RS web application,
you need to deploy your Web archive (WAR) package or the enterprise
archive (EAR) package onto the application server.