Convert List Objects to/from JSON in Java Restful Web Services

Java Libraries

Use JAR files which are listed below:

antlr-2.7.7.jar
asm-3.1.jar
commons-logging-1.1.3.jar
dom4j-1.6.1.jar
genson-1.3.jar
hibernate-commons-annotations-4.0.2.Final.jar
hibernate-core-4.2.5.Final.jar
hibernate-jpa-2.0-api-1.0.1.Final.jar
jackson-core-asl-1.9.2.jar
jackson-jaxrs-1.9.2.jar
jackson-mapper-asl-1.9.2.jar
jackson-xc-1.9.2.jar
javassist-3.15.0-GA.jar
javax.servlet.jsp.jstl-1.2.2.jar
javax.servlet.jsp.jstl-api-1.2.1.jar
jboss-logging-3.1.0.GA.jar
jboss-transaction-api_1.1_spec-1.0.1.Final.jar
jersey-client-1.18.jar
jersey-core-1.18.jar
jersey-json-1.19.3.jar
jersey-server-1.18.jar
jersey-servlet-1.18.jar
jettison-1.1.jar
jsr311-api-1.1.1.jar
mysql-connector-java-5.1.36.jar
taglibs-standard-impl-1.2.1.jar

Create Server Project

Create Dynamic Web Project in Eclipse. Copy all jar files above to the lib directory in the project

Create ApplicationConfig Class

This class is used to register a URL pattern in Jersey to intercept HTTP calls to the service. The marshaller, Jersey intercepts the path given in @ApplicationPath annotation such as – @ApplicationPath(“api”). This class extends javax.ws.rs.core.Application. All the RESTful web services and extensions needed are registered here.

ApplicationConfig.java

package ws;

import java.util.Set;
import javax.ws.rs.core.Application;

@javax.ws.rs.ApplicationPath("api")
public class ApplicationConfig extends Application {

	@Override
	public Set<Class<?>> getClasses() {
		Set<Class<?>> resources = new java.util.HashSet<>();
		addRestResourceClasses(resources);
		return resources;
	}

	private void addRestResourceClasses(Set<Class<?>> resources) {
		resources.add(controllers.DemoRestController.class);
	}

}

Entity Class

Create entities package in server project. Create a entity class: Product.java as below

Product.java

package entities;

import java.io.Serializable;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "product")
public class Product implements Serializable {

	private static final long serialVersionUID = 1L;
	private String id;
	private String name;
	private double price;

	@XmlElement(name = "id")
	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	@XmlElement(name = "name")
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@XmlElement(name = "price")
	public double getPrice() {
		return price;
	}

	public void setPrice(double price) {
		this.price = price;
	}

	public Product(String id, String name, double price) {
		this.id = id;
		this.name = name;
		this.price = price;
	}

	public Product() {
	}

}

Create Restful Web Services

Create Restful Web Services provides application/json data for the client

package controllers;

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.core.GenericEntity;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import entities.Product;

@Path("demo")
public class DemoRestController {

	@GET
	@Path("find")
	@Produces({ MediaType.APPLICATION_JSON })
	public Response find() {
		try {
			List<Product> products = new ArrayList<Product>();
			products.add(new Product("p01", "name 1", 100));
			products.add(new Product("p02", "name 2", 200));
			products.add(new Product("p03", "name 3", 300));
			GenericEntity<List<Product>> genericEntity = new GenericEntity<List<Product>>(products){};
			return Response.ok(genericEntity, MediaType.APPLICATION_JSON).build();
		} catch (Exception e) {
			return Response.status(Response.Status.BAD_REQUEST).build();
		}
	}

}

Testing Restful Web Services

Access restful web services use the following url: http://localhost:8080/LearnJavaRestfulWebServices_Server/api/demo/find

Output

[
	{"id":"p01","name":"name 1","price":100.0},
	{"id":"p02","name":"name 2","price":200.0},
	{"id":"p03","name":"name 3","price":300.0}
]

Consume Restful Web Services from Java Application

Create Java Project in Eclipse. Add all jar files above to the project

Entity Class

Create entities package in client project. Create a entity class: Product.java as below

Product.java

package entities;

import java.io.Serializable;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "product")
public class Product implements Serializable {

	private static final long serialVersionUID = 1L;
	private String id;
	private String name;
	private double price;

	@XmlElement(name = "id")
	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	@XmlElement(name = "name")
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@XmlElement(name = "price")
	public double getPrice() {
		return price;
	}

	public void setPrice(double price) {
		this.price = price;
	}

	public Product(String id, String name, double price) {
		this.id = id;
		this.name = name;
		this.price = price;
	}

	public Product() {
	}

}

Create DemoRestClientModel

DemoRestClientModel class contain methods call restful web services

package models;

import javax.ws.rs.core.MediaType;
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.DefaultClientConfig;

public class DemoRestClientModel {

	private String BASE_URL = "http://localhost:8080/LearnJavaRestfulWebServices_Server/api/";
	private WebResource webResource;
	private Client client;

	public DemoRestClientModel() {
		this.client = Client.create(new DefaultClientConfig());
		this.webResource = this.client.resource(BASE_URL).path("demo");
	}

	public ClientResponse find() {
		ClientResponse response = null;
		try {
			WebResource resource = this.webResource;
			response = resource.path("find")
								.accept(MediaType.APPLICATION_JSON)
								.get(ClientResponse.class);
		} catch (Exception e) {
			response = null;
		}
		return response;
	}

}

Run It

package demo;

import java.util.List;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.GenericType;
import entities.Product;
import models.DemoRestClientModel;

public class Main {

	public static void main(String[] args) {

		DemoRestClientModel demoRestClientModel = new DemoRestClientModel();
		ClientResponse response = demoRestClientModel.find();
		if(response != null) {
			int statusCode = response.getStatus();
			System.out.println("Response Status: " + statusCode);
			GenericType<<Product>> genericType = new GenericType<List<Product>>(){};
			List<Product> products = response.getEntity(genericType);
			System.out.println("\nProduct List");
			for(Product product : products) {
				System.out.println("Id: " + product.getId());
				System.out.println("Name: " + product.getName());
				System.out.println("Price: " + product.getPrice());
				System.out.println("==========================");
			}
		} else {
			System.err.println("Can not access find web method");
		}

	}

}

Output

Response Status: 200

Product List
Id: p01
Name: name 1
Price: 100.0
==========================
Id: p02
Name: name 2
Price: 200.0
==========================
Id: p03
Name: name 3
Price: 300.0
==========================