You can use the Atom Syndication Format (Atom) to format
web feeds, which communicate news and updates of episodic information
about websites. Using Atom content in JAX-RS applications, you can
take advantage of web content syndication that provides the same decentralized,
dynamic mechanisms for adding new metadata and content supported by
RSS, but does so in a way that helps protect core interoperability
between implementations.
About this task
Atom is an XML-based document format that describes lists
of related information known as feeds. Feeds are composed
of a number of items, known as entries, each with an extensible set
of attached metadata. For example, each entry has a title. The primary
use for Atom format is the syndication of web content such as weblogs
and news headlines to websites, as well as publishing content directly
to user agents.
The IBM® JAX-RS
library provides a JAXB Atom model that uses the standard JAXB entity
provider for consuming and producing Atom feeds and Atom entries in
a JAX-RS application.
The JAXB Atom model is included in the
org.apache.wink.common.model.atom and org.apache.wink.common.model.synd Java™ packages in the Apache Wink-based IBM JAX-RS library JAR. An application
can use classes such as a JAXB annotated org.apache.wink.common.model.atom.AtomFeed
to read and write ATOM feeds.
Procedure
- 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 you want to 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.
- Implement
JAXB-based ATOM content for requests and responses
- You can represent Atom documents using JAXB annotated
objects because the Atom format is based on XML. Therefore, one way
to implement a resource method that consumes and produces Atom feeds
and Atom entries is to return a JAXB annotated object that uses the
Atom model. The JAX-RS library provides an Atom model based on JAXB.
- 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.
Results
You have developed and deployed a JAX-RS web application
on the application server that uses Atom content for requests and
responses.