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

Use handlers to enhance request and response processing

We can implement handlers on the server-side of a Java API for RESTful Web Services (JAX-RS) application to enhance request and response processing.

To perform additional operations on messages, we can create a handler that is applied during the processing of a request and a response. Handlers are invoked on every request and response. Custom server-side request handlers are applied after the resource method is found. Custom server-side response handlers are applied before the response is sent back to the client.

There are three distinct handler chains: a request handler chain, a response handler chain, and an error handler chain. Normal requests invoke the request handler chain to find the resource and invoke the resource method. After, the response handler chain then populates the response headers and content. If an error occurs, the error handler chain is invoked. The error handler chain invokes the proper JAX-RS error handling mechanism and then populates the response headers and content.

There are system handlers and user handlers. System handlers implement the core runtime environment for IBM JAX-RS. We can write user handlers to customize the behavior of the handler chain for the JAX-RS application and to add unique functionality to the handler.


Procedure

  1. Configure the development environment

    Before you start developing JAX-RS applications, set up your development environment by adding the JAX-RS libraries on the classpath.

  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.

  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:

  4. Implement user handlers for the JAX-RS application

    We can develop user handlers to customize the behavior of a handler chain and to add unique functionality to the handler. By implementing user handlers on the server-side of JAX-RS applications, we can enhance request and response processing.

  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.

  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

Deploy JAX-RS web applications


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