RESTful Web Services (JAX-RS) @QueryParam Example

@QueryParam can be used in case of filtering . When you want show both param as well value in url.
For example: Lets say you are showing list of customers on a website and you can show 10 at a time. When user click next , he will see next 10 customers, so in this case, we can use @QueryParam may look something like this

1) Follow steps on RESTful Web Services json example to create simple RESTful web services which uses @PathParam.
2) Change CountryRestService.java to use @QueryParam as below.

package org.arpit.java2blog.jaxrs;

import java.util.ArrayList;
import java.util.List;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;

import org.arpit.java2blog.bean.Country;
/*
 * author: Arpit Mandliya
 * */
@Path("/countries")
public class CountryRestService {

 @GET
 @Produces(MediaType.APPLICATION_JSON)
 public List getCountries()
 {
 List listOfCountries = new ArrayList();
 listOfCountries=createCountryList();
 return listOfCountries;
 }

 @GET
 @Path("/country")
 @Produces(MediaType.APPLICATION_JSON)
 public Country getCountryById(@QueryParam("id") int id,@QueryParam("countryName") String countryName)
 {
 List listOfCountries = new ArrayList();
 listOfCountries=createCountryList();

 for (Country country: listOfCountries) {
 if(country.getId()==id && country.getCountryName().equalsIgnoreCase(countryName))
 return country;
 }

 return null;
 }

// Utiliy method to create country list.
 public List createCountryList()
 {
 Country indiaCountry=new Country(1, "India");
 Country chinaCountry=new Country(4, "China");
 Country nepalCountry=new Country(3, "Nepal");
 Country bhutanCountry=new Country(2, "Bhutan");

 List listOfCountries = new ArrayList();
 listOfCountries.add(indiaCountry);
 listOfCountries.add(chinaCountry);
 listOfCountries.add(nepalCountry);
 listOfCountries.add(bhutanCountry);
 return listOfCountries;
 }
}

That’s all. We need to run the application now.

4) Now pass country id and country name as parameter to url.

“http://localhost:8080/JAXRSJsonExample/rest/countries/country?id=3&countryName=Nepal”.

We are done with Restful web services json QueryParam example. If you are still facing any issue, please comment.