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Implement RESTful views of EJB applications using JAX-RS

If we have enterprise JavaBeans (EJB) applications, we 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.

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.

Use the EJB 3.1 specification, we 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 based on the public methods of our bean class. No-interface view enterprise beans can be more simple to develop than a local view enterprise bean for the following reasons:

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.


Tasks

  1. Configure the development environment.

    1. Before starting developing JAX-RS applications, we must set up the 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 the application, we can make the service more useful and easier to develop.

  3. Configure the JAX-RS application.

    We can configure JAX-RS applications in multiple . To take advantage of the Java EE 6 functionality, we can use the annotation scanning capabilities. By using annotation scanning, we can omit a JAX-RS javax.ws.rs.core.Application subclass or have a minimally defined javax.ws.rs.core.Application subclass. Alternatively, we can specify the IBM JAX-RS servlet or filter to use the functionality available in the IBM JAX-RS servlet and filter.

    Using one of the JAX-RS Version 1.1 configuration methods, we can omit a javax.ws.rs.core.Application subclass in the 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. We might want to use this method when we 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, we 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 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, to specify security constraints or roles, or we want to take advantage of other features enabled using a web.xml file, specify the information in a web.xml file.

    Choose one of the following three methods to configure the JAX-RS application:

    • Configure JAX-RS applications using JAX-RS 1.1 methods

      Use this method to use the annotation scanning capabilities or to use the JAX-RS 1.1 configuration methods. 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 to specify features enabled using servlet initialization parameters to change the behavior and ensure that we get the IBM JAX-RS servlet. When using servlets, we 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 to use the filter when we have JSPs, other servlets and filters, and JAX-RS resources with a mix of URL patterns. We 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. We 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 developing the Java class files for our JAX-RS web application and edit the web.xml file to enable the JAX-RS servlet, we are ready to assemble the application. Assemble the web application into a web archive (WAR) package. We can assemble the WAR package into an EAR package if required.

  6. Deploy JAX-RS web applications.

    1. After assembling the JAX-RS web application, we need to deploy the web archive (WAR) package or the EAR package onto the application server.

We have enabled an enterprise bean so that JAX-RS resources are exposed for consumption.

  • Implement RESTful views of a no-interface EJB
  • Implement RESTful views of an EJB with local interfaces
  • Developing a session bean to have a No-Interface Local view
  • Developing singleton session beans
  • Web services specifications and APIs
  • EJB application specifications and APIs