RESTful Services CRUD with Java JAX-RS Jersey

REST stands for Representational State Transfer and  it’s an architecture style for for creating network based applications. In my previous tutorial, we saw about a creating a hello world application on RESTful web services using Java JAX-RS in Jersey.

JAX-RS is the Java API specification and Jersey is its reference implementation. This tutorial is a continuation in that series. We will see how to create a CRUD (Create, Read, Update and Delete) application in RESTful services with Java JAX-RS using Jersey. To know about web services in general, read the introduction to web services tutorial.

RESTful Web Services CRUD Example

Download

Create a Dynamic web application. I am using Eclipse EE edition. Refer the previous tutorial to do this step by step. Then copy all the Jersey JAR files into the lib folder. Jersey and its dependent JAR files are available in its download bundle from its official site.

Following is the data model for this RESTful CRUD services.

package com.javapapers.webservices.rest.jersey;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Animal {
	private String id;
	private String name;
	private String type;

	public Animal() {

	}

	public Animal(String id, String name, String type) {
		super();
		this.id = id;
		this.name = name;
		this.type = type;
	}

	public String getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

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

	public String getType() {
		return type;
	}

	public void setType(String type) {
		this.type = type;
	}

}

AnimalResource.java

Following is a RESTful web service resource file. This resource demonstrates the basic GET, PUT and DELETE operations. Jersey annotations are used to mark each method for its type and content response media-type.

package com.javapapers.webservices.rest.jersey;

import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.PUT;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Request;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.UriInfo;
import javax.xml.bind.JAXBElement;

public class AnimalResource {

	@Context
	UriInfo uriInfo;
	@Context
	Request request;
	String id;

	AnimalService animalService;

	public AnimalResource(UriInfo uriInfo, Request request, String id) {
		this.uriInfo = uriInfo;
		this.request = request;
		this.id = id;
		animalService = new AnimalService();
	}

	@GET
	@Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
	public Animal getAnimal() {
		Animal animal = animalService.getAnimal(id);
		return animal;
	}

	@GET
	@Produces(MediaType.TEXT_XML)
	public Animal getAnimalAsHtml() {
		Animal animal = animalService.getAnimal(id);
		return animal;
	}

	@PUT
	@Consumes(MediaType.APPLICATION_XML)
	public Response putAnimal(JAXBElement<Animal> animalElement) {
		Animal animal = animalElement.getValue();
		Response response;
		if (animalService.getAnimals().containsKey(animal.getId())) {
			response = Response.noContent().build();
		} else {
			response = Response.created(uriInfo.getAbsolutePath()).build();
		}
		animalService.createAnimal(animal);
		return response;
	}

	@DELETE
	public void deleteAnimal() {
		animalService.deleteAnimal(id);
	}

}

Method	Description
GET	Is used to read from a REST resource.
PUT	Is used for Create/Updating a REST resource.
POST	Generally used for new resource creation.
DELETE	To delete a REST resource.

AnimalsResource.java

This REST resource maps to the path given in annotation “/animals”.

package com.javapapers.webservices.rest.jersey;

import java.io.IOException;
import java.util.List;

import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.Consumes;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Request;
import javax.ws.rs.core.UriInfo;

@Path("/animals")
public class AnimalsResource {

	@Context
	UriInfo uriInfo;
	@Context
	Request request;

	AnimalService animalService;

	public AnimalsResource() {
		animalService = new AnimalService();
	}

	@GET
	@Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
	public List<Animal> getAnimals() {
		return animalService.getAnimalAsList();
	}

	@GET
	@Produces(MediaType.TEXT_XML)
	public List<Animal> getAnimalsAsHtml() {
		return animalService.getAnimalAsList();
	}

	// URI: /rest/animals/count
	@GET
	@Path("count")
	@Produces(MediaType.TEXT_PLAIN)
	public String getCount() {
		return String.valueOf(animalService.getAnimalsCount());
	}

	@POST
	@Produces(MediaType.TEXT_HTML)
	@Consumes(MediaType.APPLICATION_FORM_URLENCODED)
	public void createAnimal(@FormParam("id") String id,
			@FormParam("animalname") String name,
			@FormParam("animaltype") String type,
			@Context HttpServletResponse servletResponse) throws IOException {
		Animal animal = new Animal(id, name, type);
		animalService.createAnimal(animal);
		servletResponse.sendRedirect("./animals/");
	}

	@Path("{animal}")
	public AnimalResource getAnimal(@PathParam("animal") String id) {
		return new AnimalResource(uriInfo, request, id);
	}

}

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" 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>RESTful Services CRUD</display-name>
 <servlet>
    <servlet-name>RESTful Jersey CRUD Service</servlet-name>
    <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
    <init-param>
        <param-name>jersey.config.server.provider.packages</param-name>
        <param-value>com.javapapers.webservices.rest.jersey</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>RESTful Jersey CRUD Service</servlet-name>
    <url-pattern>/rest/*</url-pattern>
  </servlet-mapping>
</web-app>

Service and DAO Classes

package com.javapapers.webservices.rest.jersey;

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

public class AnimalService {

	AnimalDao animalDao;

	public AnimalService() {
		animalDao = AnimalDao.instance;
	}

	public void createAnimal(Animal animal) {
		animalDao.getAnimals().put(animal.getId(), animal);
	}

	public Animal getAnimal(String id) {
		return animalDao.getAnimals().get(id);
	}

	public Map<String, Animal> getAnimals() {
		return animalDao.getAnimals();
	}

	public List<Animal> getAnimalAsList() {
		List<Animal> animalList = new ArrayList<Animal>();
		animalList.addAll(animalDao.getAnimals().values());
		return animalList;
	}

	public int getAnimalsCount() {
		return animalDao.getAnimals().size();
	}

	public void deleteAnimal(String id) {
		animalDao.getAnimals().remove(id);
	}

}

package com.javapapers.webservices.rest.jersey;

import java.util.HashMap;
import java.util.Map;

public enum AnimalDao {
	instance;

	private Map<String, Animal> animals = new HashMap<String, Animal>();

	private AnimalDao() {

		//pumping-in some default data
		Animal animal = new Animal("1", "Lion", "Wild");
		animals.put("1", animal);
		animal = new Animal("2", "Crocodile", "Wild");
		animals.put("2", animal);

	}

	public Map<String, Animal> getAnimals() {
		return animals;
	}

}

UI to Create Operation

Put this file createanimal.html in WebContent folder.

<!DOCTYPE html>
<html>
<head>
<title>Create Animal</title>
</head>
<body>
	<div style="padding-left:100px;font-family: monospace;">
		<h2>Create Animal</h2>
		<form action="rest/animals" method="POST">
			<div style="width: 200px; text-align: left;">
				<div style="padding:10px;">
					Animal ID: <input name="id" />
				</div>
				<div style="padding:10px;">
					Animal Name: <input name="animalname" />
				</div>
				<div style="padding:10px;">
					Animal Type: <input name="animaltype" />
				</div>
				<div style="padding:10px;text-align:center">
					<input type="submit" value="Submit" />
				</div>
			</div>
		</form>
	</div>
</body>
</html>

RESTful Web Services CRUD Output

 

Download the RESTful Java Web Service CRUD Example

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