Naresh's Blog

In this entry, we will use the HelloWorldWebApp created in the previous entry. We will modify the resource, so that it takes name of a person as a query parameter and greets him/her. If no name is provided, it will give the general Hello World! message.

   And here are the steps:  

• Overwrite the previously implemented sayHello method with the following:

    @GET
    @Produces("text/plain")
    public String sayHello(@QueryParam("name") String name) {
        if (name != null) {
            // if the query parameter "name" is there
            return "Hello " + name + "!";
        }
        return "Hello World!";
    }       

• Import the class javax.ws.rs.QueryParam.
• Redeploy the application and enter http://localhost:8080/HelloWorldWebapp/resources/hello?name=Rama in a browser. You will see that response Hello Rama!. If the query parameter name is not specified the response would be Hello World!.
  

So how does this work?

          Here we are using a new annotation @QueryParam. It is an annotation provided by the JAX-RS API. This annotation takes care of mapping a query parameter in a request to a method parameter.

           In this example, we have used this annotation to map the query parameter name to the method parameter name. When a request is sent for the resource with some query parameter value for name, it gets set to the method parameter. For this to happen, the query parameter needs to be mapped to the method parameter. This is done by prefixing the method parameter declaration with @QueryParam and specifying the query parameter name as a string parameter for the annotation. In our example, it is achieved by doing this:

public String sayHello(@QueryParam("name") String name) {