If you have enterprise JavaBeans (EJB)
applications, you can expose a RESTful interface to the enterprise
bean using Java™ API for RESTful
Web Services (JAX-RS). By implementing JAX-RS annotated enterprise
beans, you keep the EJB functionality including transaction support,
injection of Java EE components
and resources, and other EJB session bean capabilities.
About this task
Before EJB 3.1, enterprise beans that required an EJB
local client view also needed a separate Java interface,
usually located in a separate file, that declared the local view methods.
The enterprise bean specified that it implemented the EJB local view
interface using deployment descriptors or EJB annotations.
Using
the EJB 3.1 specification, you have the option of exposing a local
view of an enterprise bean without an explicit EJB local interface.
Instead, the enterprise bean has a no-interface client view that
is based on the public methods of your bean class. No-interface view
enterprise beans can be more simple to develop than a local view enterprise
bean for the following reasons:
- No-interface view enterprise beans do not require a separate Java interface declaration
- No-interface view enterprise beans do not require specifying additional
metadata in the deployment descriptor or when using annotations
See the EJB 3.1 specification for more details on the no-interface
views of an enterprise bean.
JAX-RS supports the use of enterprise
beans that declare a local business interface and no-interface view
enterprise beans.
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 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.
- Implement RESTful views of enterprise beans.
You
can implement RESTful views of enterprise beans using JAX-RS for a
stateless or singleton enterprise bean that uses a no-interface view
or a local business interface.
- 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 enabled an enterprise bean so that JAX-RS resources
are exposed for consumption.