Use custom entity formats

Even though the Java API for RESTful Web Services (JAX-RS) runtime environment includes several entity providers for handling serialization from and deserialization to Java types, it does not support all possible media types. We can develop a custom entity provider to handle binding Java types to message bodies.

If our JAX-RS web application requires that additional Java types or media types are supported beyond what the JAX-RS APIs support, we can add a custom entity provider to the application. Any custom-defined entity provider takes precedence over the entity providers included in the JAX-RS runtime environment. Unlike resources, providers are always singleton 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 classpath.

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 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, 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 custom entity formats.

   1. If our JAX-RS web application requires support for additional Java types or media types that are not supported by the JAX-RS APIs, we can add a custom entity provider to the application.

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 application archive (WAR) package. We can assemble the WAR package into an enterprise archive (EAR) package, if required.

6. Deploy JAX-RS web applications.

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

We have developed and deployed a JAX-RS web application containing a custom entity provider.

Implement custom entity formats

Web services specifications and APIs