WAS v8.5 > End-to-end paths > Web services - RESTful services

Use content negotiation to serve multiple content types in JAX-RS applications

One of the advantages of RESTful applications is the ability to return different representations of resources. With Representational State Transfer (REST), clients and servers can exchange resources of the same media type or use differing media types. Content negotiation enables clients and servers to agree on the content format used to exchange data.

Resources are represented by many different formats. XML, JSON, Atom, plain text, PNG, JPEG, GIF, and custom or proprietary formats are used to represent resources. Representational State Transfer (REST) provides the flexibility to represent a single resource in multiple formats.

Depending on the requirements of the application, resources can return representations in a single format or in different formats, depending on the request. For example, resources accessed using JavaScript clients might prefer JSON representations because JSON is easy to consume. However, other clients prefer XML.

Use content negotiation to serve multiple formats to clients. Content negotiation is the method in which the client and server agree on the response content type to use. There are three types of content negotiation that affect the response. We can use content negotiation based on the URL, based on a request parameter, or based on HTTP headers.

1. Configure the development environment
   • Set up a development environment for JAX-RS applications
     
   • Development and assembly tools
     
   • Directory conventions
     

2. 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 the application, we can make the service more useful and easier to develop.

   • Define the resources in RESTful applications
   • Define the URI patterns for resources in RESTful applications
   • Define resource methods for RESTful applications
   • Define the HTTP headers and response codes for RESTful applications
   • Define media types for resources in RESTful applications
   • Define parameters for request representations to resources in RESTful applications
   • Define exception mappers for resource exceptions and errors

3. Configure the JAX-RS application

   We can configure JAX-RS applications in multiple ways depending on your needs. 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 v1.1 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. You 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 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 your JAX-RS application:

   • Configure JAX-RS applications using JAX-RS 1.1 methods
   • Configure web.xml for JAX-RS servlets
   • Configure web.xml for JAX-RS filters

4. Implement content negotiation to serve multiple content types

   Use content negotiation to determine the best resource representation for the server to return to the client. We can implement content negotiation based on URL patterns, request parameters, or HTTP headers.

   • Implement content negotiation based on URL patterns
   • Implement content negotiation based on request parameters
   • Implement content negotiation based on HTTP headers

5. Assemble JAX-RS web applications

   After you develop the Java class files for the JAX-RS web application and edit web.xml to enable the JAX-RS servlet, you are ready to assemble the application. Assemble the web application into a WAR package. We can assemble the WAR package into an EAR package if required.

   • Assemble JAX-RS web applications
     
   • Development and assembly tools
     

6. Deploy JAX-RS web applications

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

Related

Implement content negotiation based on URL patterns
Implement content negotiation based on HTTP headers
Implement content negotiation based on request parameters
Web services specifications and APIs

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