Web Application Description Language (WADL) is a description
language for HTTP-based applications. It is currently a World Wide
Web Consortium (W3C) Member Submission. WADL can be used by programs
to give information about the service in a machine-processable method.
For instance, you can use an Extensible Stylesheet Transformation
(XSLT) document to transform the WADL documentation by using a custom
XSLT and a XSLT processor.
About this task
By default, a WADL document can be requested for a particular
resource by invoking an HTTP OPTIONS request for any Java™ API for RESTful Web Services (JAX-RS) URL.
You can issue an OPTIONS request with most HTTP clients. The WADL
document returned from the request describes the resource using information
from the JAX-RS annotations.
WADL is a developing standard which
helps describe the services available to users. WADL documents are
written in XML. Using XSTL or XML parsers, developers can generate
documentation for the service. In some cases, users may develop clients
to dynamically understand the RESTful service by inspecting the WADL
document.
Using IBM® JAX-RS,
developers can generate a JAXB XML representation of a WADL document
describing all of the resources available in the application. The
JAXB representation can be returned from a JAX-RS resource method.
Then, the WADL document resource is treated like any other JAX-RS
resource and can be used by clients.
- 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 class path.
- 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 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.
- Use WADL to generate service documentation. You
can also build your own WADL document by using the org.apache.wink.common.model.wadl.WADLGenerator.
WADLGenerator builds a Java Architecture
for XML Binding (JAXB) annotated object model so you can easily return
it as an entity response in an @OPTIONS resource
method as the response entity.
- 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 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.
Results
You have added a WADL service document to your application
to enable clients to retrieve a representation of your service. By
default, you can also issue OPTIONS requests to your resources to
retrieve a WADL representation of the individual resource. If you
have chosen to do so, you can disable the automatic generation of
a WADL document for OPTIONS requests.