Implementing RESTful views of EJB applications using JAX-RS

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

  1. Configure the development environment.
    1. Before you start developing JAX-RS applications, you must set up your development environment by adding the JAX-RS libraries on the class path.
  2. Define the resources in JAX-RS web applications.
    1. 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.
  3. 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.

  4. 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.
  5. Assemble JAX-RS web applications.
    1. 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.
  6. Deploy JAX-RS web applications.
    1. 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.