Using JSON content in JAX-RS application requests and responses

JavaScript Object Notation (JSON) is a common media format that RESTful services consume and produce. You can use this lightweight data-interchange format that is based on the object-literal notation of JavaScript to exchange data.

About this task

JSON is a popular data format that is programming-language neutral. Multiple web browsers and JavaScript libraries such as Dojo provide support for JSON. WebSphere® supports the Jackson and JavaScript Object Notation (JSON4J) libraries.

The Jackson library is a JSON processor (both parser and generator) based on streaming API for XML (StAX) pull parser technology. It provides basic JSON reading and writing (parsing and generating), a full node-based tree model, as well as object-to-JSON data binding.

You can use the Jackson library to unmarshal and marshal JSON data to and from Plain Old Java™ Objects (POJOs) and Java Architecture for XML Binding (JAXB) objects. To use Jackson to process JSON data, you must include the Jackson libraries in the class path. After adding Jackson to the class path, you use POJOs and JAXB objects to represent request and response message bodies. Jackson is included in the server-side run time of this product.

The JSON4J library is an implementation of a set of JSON handling classes for use within Java environments. The JSON4J library provides a simple Java model for constructing and manipulating data to be rendered as JSON data.

You can use the JSON4J library to output JSON data. To use JSON4J types as supported entity types, you must include the JSON4J library in the class path. After adding JSON4J to the class path, you can use the JSONObject, and the JSONArray classes from the JSON4J library as types to represent request and response message bodies. JSON4J is included in the server-side runtime environment of this product.

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 must 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 with 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 a resource method using JSON content for a request and response entity.
   1. RESTful services can consume and produce content using the JSON format.
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 application 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 must deploy your web archive (WAR) package or the enterprise archive (EAR) package onto the application server.

Results

You have developed and deployed a JAX-RS web application on the application server that uses JSON4J libraries to process JSON content for requests and responses.