JAX-RS @QueryParam with @DefaultValue

In this tutorial we are going to see how set default value to query parameters in RESTful web service using @DefaultValue
1. Create new Dynamic web project by choosing File –> New –> Dynamic Web Project.

2. Create the Project called RESTful-WebService
3. Add the following jar into WEF-INF/lib folder

4. Create package called com.javatutorialscorner.jaxrs.queryparam under RESTful-WebService

5. Create Java class QueryParamService under com.javatutorialscorner.jaxrs.queryparam package

QueryParamService .java

package com.javatutorialscorner.jaxrs.queryparam;

import javax.ws.rs.DefaultValue;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.Response;

@Path("/tutorials")
public class QueryParamService {

 @GET
 @Path("/java-tutorial")
 public Response getTutorial(
   @DefaultValue("www.javatutorialscorner.com") @QueryParam("site") String site,
   @DefaultValue("Web Service Tutorial") @QueryParam("tutorial") String tutorial,
   @DefaultValue("1") @QueryParam("rank") int rank) {
  return Response
    .status(200)
    .entity("Web Site : " + site + "  Tutorial : " + tutorial
      + " Rank : " + rank).build();
 }
}

In above class @QueryParam used to get the value of URL query parameter into Java Class. If there is no query param in URL then default value set to the corresponding fields using @DefaultValue annotation

6.Configure Jersey Servlet Dispatcher
you need to configure REST as servlet in web.xml.
web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>JAX-RS-Path</display-name>
<servlet>
  <servlet-name>jersey-serlvet</servlet-name>
  <servlet-class>
                     com.sun.jersey.spi.container.servlet.ServletContainer
                </servlet-class>
  <init-param>
       <param-name>com.sun.jersey.config.property.packages</param-name>
       <param-value>com.javatutorialscorner.jaxrs.queryparam</param-value>
  </init-param>
  <load-on-startup>1</load-on-startup>
 </servlet>
 
 <servlet-mapping>
  <servlet-name>jersey-serlvet</servlet-name>
  <url-pattern>/rest/*</url-pattern>
 </servlet-mapping>
</web-app>

The servlet class available in jersey com.sun.jersey.spi.container.servlet.ServletContainer. The init param com.sun.jersey.config.property.package is used to define in which package jersey will look for the service classes.This package points to your resource class package. URL pattern is the part of base URL

Now you can run the service and access the service by calling the following URL

http://localhost:8080/RESTful-WebService/rest/tutorials/java-tutorial

or

http://localhost:8080/RESTful-WebService/rest/tutorials/java-tutorial?site=www.javatutorialscorner.com&tutorial=RESTful%20WebService&rank=1

you can call the service by using web browser or from client class.
Web browser call
Output with parameter

Output with default value

Create Client
1.Create package called com.javatutorialscorner.jaxrs.client under RESTful-WebService project
2.Create Client Java Class RESTfulClient under com.javatutorialscorner.jaxrs.client package
RESTfulClient .java

package com.javatutorialscorner.jaxrs.client;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;

public class RESTfulClient {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  String baseURI = "http://localhost:8080/RESTful-WebService";
  ClientConfig config = new DefaultClientConfig();
  Client client = Client.create(config);
  WebResource service = client.resource(baseURI);
  System.out.println("output with Query param");
  System.out.println(service.path("rest").path("tutorials/java-tutorial")
    .queryParam("site", "www.javatutorialscorner.com")
    .queryParam("tutorial", "RESTful WebService")
    .queryParam("rank", "1").get(ClientResponse.class)
    .getEntity(String.class));
  System.out.println("output with out Query param");
  System.out.println(service.path("rest").path("tutorials/java-tutorial")
    .get(ClientResponse.class).getEntity(String.class));
 }

}

Now you can run the client and see the following output in console

output with Query param

Web Site : www.javatutorialscorner.com Tutorial : RESTful WebService Rank : 1

output with out Query param

Web Site : www.javatutorialscorner.com Tutorial : Web Service Tutorial Rank : 1