Restful Web Services Tutorial in Java

Filed Under: Java

Welcome to Restful Web Services Tutorial in Java. REST is the acronym for REpresentational State Transfer. REST is an architectural style for developing applications that can be accessed over the network. REST architectural style was brought in light by Roy Fielding in his doctoral thesis in 2000.

Restful Web Services

Restful Web Services is a stateless client-server architecture where web services are resources and can be identified by their URIs.

REST Client applications can use HTTP GET/POST methods to invoke Restful web services. REST doesn’t specify any specific protocol to use, but in almost all cases it’s used over HTTP/HTTPS. When compared to SOAP web services, these are lightweight and doesn’t follow any standard. We can use XML, JSON, text or any other type of data for request and response.

Java RESTful Web Services API

Java API for RESTful Web Services (JAX-RS) is the Java API for creating REST web services. JAX-RS uses annotations to simplify the development and deployment of web services. JAX-RS is part of JDK, so you don’t need to include anything to use it’s annotations.

Restful Web Services Annotations

Some of the important JAX-RS annotations are:

  • @Path: used to specify the relative path of class and methods. We can get the URI of a webservice by scanning the Path annotation value.
  • @GET, @PUT, @POST, @DELETE and @HEAD: used to specify the HTTP request type for a method.
  • @Produces, @Consumes: used to specify the request and response types.
  • @PathParam: used to bind the method parameter to path value by parsing it.

Restful Web Services and SOAP

  1. SOAP is a protocol whereas REST is an architectural style.
  2. SOAP server and client applications are tightly coupled and bind with the WSDL contract whereas there is no contract in REST web services and client.
  3. Learning curve is easy for REST when compared to SOAP web services.
  4. REST web services request and response types can be XML, JSON, text etc. whereas SOAP works with XML only.
  5. JAX-RS is the Java API for REST web services whereas JAX-WS is the Java API for SOAP web services.

REST API Implementations

There are two major implementations of JAX-RS API.

  1. Jersey: Jersey is the reference implementation provided by Sun. For using Jersey as our JAX-RS implementation, all we need to configure its servlet in web.xml and add required dependencies. Note that JAX-RS API is part of JDK not Jersey, so we have to add its dependency jars in our application.
  2. RESTEasy: RESTEasy is the JBoss project that provides JAX-RS implementation.

Java Restful Web Services Tutorial

Let’s see how easy to create Restful web service using Jersey and then RESTEasy. We will be exposing following methods over HTTP and use Chrome Postman extension to test these.

URI HTTP Method Description
/person/{id}/getDummy GET Returns a dummy person object
/person/add POST Adds a person
/person/{id}/delete GET Delete the person with ‘id’ in the URI
/person/getAll GET Get all persons
/person/{id}/get GET Get the person with ‘id’ in the URI

Jersey Restful Web Services

Create a dynamic web project and then convert it to Maven to get the skeleton of your web services project. Below image shows the project structure of the final project.

JAXRS Jersey Project

Let’s look at the Jersey dependencies we have in pom.xml file.


<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>JAXRS-Example</groupId>
  <artifactId>JAXRS-Example</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  
  <dependencies>
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-server</artifactId>
            <version>1.19</version>
        </dependency>
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-servlet</artifactId>
            <version>1.19</version>
        </dependency>
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-client</artifactId>
            <version>1.19</version>
        </dependency>
  </dependencies>
  
  <build>
    <sourceDirectory>src</sourceDirectory>
    <plugins>
      <plugin>
        <artifactId>maven-war-plugin</artifactId>
        <version>2.6</version>
        <configuration>
          <warSourceDirectory>WebContent</warSourceDirectory>
          <failOnMissingWebXml>false</failOnMissingWebXml>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <configuration>
          <source>1.7</source>
          <target>1.7</target>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

We are not required to add jersey-client dependencies but if you are writing java program to invoke a REST web service using Jersey then it’s required.

Now let’s look at the deployment descriptor to learn how to configure Jersey to create our web application.


<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>JAXRS-Example</display-name>

<!-- Jersey Servlet configurations -->
    <servlet>
    <servlet-name>Jersey REST Service</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.journaldev</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>Jersey REST Service</servlet-name>
    <url-pattern>/*</url-pattern>
  </servlet-mapping>
  <!-- Jersey Servlet configurations -->

</web-app>

That’s all is required to plugin Jersey into our web application, in our java code we will be using JAX-RS annotations. Notice the value of init parameter com.sun.jersey.config.property.packages to provide package that will be scanned for web service resources and methods.

REST Example Model Classes

First of all we will create two model beans – Person for our application data and Response for sending response to client systems. Since we will be sending XML response, the beans should be annotated with @XmlRootElement, hence we have this class.


package com.journaldev.jaxrs.model;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement (name="person")
public class Person {
	private String name;
	private int age;
	private int id;

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}
	
	@Override
	public String toString(){
		return id+"::"+name+"::"+age;
	}

}

package com.journaldev.jaxrs.model;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Response {

	private boolean status;
	private String message;

	public boolean isStatus() {
		return status;
	}

	public void setStatus(boolean status) {
		this.status = status;
	}

	public String getMessage() {
		return message;
	}

	public void setMessage(String message) {
		this.message = message;
	}
}

REST Web Services Tutorial Services

Based on our URI structure, below is the service interface and it’s implementation code.


package com.journaldev.jaxrs.service;

import com.journaldev.jaxrs.model.Person;
import com.journaldev.jaxrs.model.Response;

public interface PersonService {

	public Response addPerson(Person p);
	
	public Response deletePerson(int id);
	
	public Person getPerson(int id);
	
	public Person[] getAllPersons();

}

package com.journaldev.jaxrs.service;


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

import javax.ws.rs.Consumes;
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.MediaType;

import com.journaldev.jaxrs.model.Person;
import com.journaldev.jaxrs.model.Response;

@Path("/person")
@Consumes(MediaType.APPLICATION_XML)
@Produces(MediaType.APPLICATION_XML)
public class PersonServiceImpl implements PersonService {

	private static Map<Integer,Person> persons = new HashMap<Integer,Person>();
	
	@Override
	@POST
    @Path("/add")
	public Response addPerson(Person p) {
		Response response = new Response();
		if(persons.get(p.getId()) != null){
			response.setStatus(false);
			response.setMessage("Person Already Exists");
			return response;
		}
		persons.put(p.getId(), p);
		response.setStatus(true);
		response.setMessage("Person created successfully");
		return response;
	}

	@Override
	@GET
    @Path("/{id}/delete")
	public Response deletePerson(@PathParam("id") int id) {
		Response response = new Response();
		if(persons.get(id) == null){
			response.setStatus(false);
			response.setMessage("Person Doesn't Exists");
			return response;
		}
		persons.remove(id);
		response.setStatus(true);
		response.setMessage("Person deleted successfully");
		return response;
	}

	@Override
	@GET
	@Path("/{id}/get")
	public Person getPerson(@PathParam("id") int id) {
		return persons.get(id);
	}
	
	@GET
	@Path("/{id}/getDummy")
	public Person getDummyPerson(@PathParam("id") int id) {
		Person p = new Person();
		p.setAge(99);
		p.setName("Dummy");
		p.setId(id);
		return p;
	}

	@Override
	@GET
	@Path("/getAll")
	public Person[] getAllPersons() {
		Set<Integer> ids = persons.keySet();
		Person[] p = new Person[ids.size()];
		int i=0;
		for(Integer id : ids){
			p[i] = persons.get(id);
			i++;
		}
		return p;
	}

}

Most of the code is self explanatory, spend some time to familiarize yourself with JAX-RS annotations @Path, @PathParam, @POST, @GET, @Consumes and @Produces.

Restful Web Services Test

That’s it. Our web service is ready, just export it as WAR file and put it inside Tomcat webapps directory or deploy into any other container of your choice.

Below are some of the tests performed using Postman chrome extension for this web service. Note that we have to provide Accept and Content-Type values as “application/xml” in request header as shown in below image.

JAXRS Headers Accept

  • getDummy
    Restful web services java
  • add
    Java Restful web services tutorial
  • get
    Rest Web Services tutorial
  • getAll
    Jersey rest web services
  • delete
    Jersey REST API

That’s all for creating web services using Jersey JAX-RS implementation. As you can see that most of the code is using JAX-RS annotations and Jersey is plugged in through deployment descriptor and dependencies.

RESTEasy RESTful Web Services Example

We will use all the business logic developed in Jersey project, but rather than making changes to the same project, I have created a new project. Create a dynamic web project and convert it to Maven project. Then copy all the java classes – Person, Response, PersonService and PersonServiceImpl. Below is the final project after we are done with all the changes.

JAXRS RestEasy Project

Add below RESTEasy dependencies in pom.xml file.


<dependency>
	<groupId>org.jboss.resteasy</groupId>
	<artifactId>resteasy-jaxrs</artifactId>
	<version>3.0.13.Final</version>
</dependency>
<dependency>
	<groupId>org.jboss.resteasy</groupId>
	<artifactId>resteasy-jaxb-provider</artifactId>
	<version>3.0.13.Final</version>
</dependency>

Below is the web.xml file where we are configuring Resteasy servlet.


<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>JAXRS-Example-RestEasy</display-name>
     
    <listener>
      <listener-class>
         org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap
      </listener-class>
   	</listener>
   
    <servlet>
        <servlet-name>resteasy-servlet</servlet-name>
        <servlet-class>
            org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
        </servlet-class>
        <init-param>
        <param-name>javax.ws.rs.Application</param-name>
        <param-value>com.journaldev.jaxrs.resteasy.app.MyApp</param-value>
    </init-param>
    </servlet>
  
    <servlet-mapping>
        <servlet-name>resteasy-servlet</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
	
</web-app>

Notice the init-param where are providing MyApp class as value, here we are extending javax.ws.rs.core.Application class as shown below.


package com.journaldev.jaxrs.resteasy.app;

import java.util.HashSet;
import java.util.Set;

import javax.ws.rs.core.Application;

import com.journaldev.jaxrs.service.PersonServiceImpl;

public class MyApp extends Application {
	
	private Set<Object> singletons = new HashSet<Object>();

	public MyApp() {
		singletons.add(new PersonServiceImpl());
	}

	@Override
	public Set<Object> getSingletons() {
		return singletons;
	}

}

RESTEasy Web Services Test

That’s it. Our web service is ready with RESTEasy JAX-RS implementation. Below are some of the output from Postman chrome extension test.

  • getDummy
    rest services in java, rest client java, java rest api, REST Tutorial
  • add
    Restful web services java, Java Restful web services
  • get
    Restful Web Services

That’s all for Restful Web Services Tutorial, I hope you learned about JAX-RS annotations and understood the benefits of having standard API that helped us in reusing code and moving from Jersey to RESTEasy so easy.

Comments

  1. Dallas Jones says:

    Excellent example, much appreciated.

  2. Venky says:

    Great article.

    One correction. In Response class, we need to add the following to avoid error.

    @Produces (MediaType.APPLICATION_XML)
    @XmlRootElement (name = “response”)

  3. Subhash says:

    I copied your files as it is, however I am getting below error when I am trying to start server. I am using Tomcat 8.5 and Java 11.

    .
    .
    .
    INFO: Scanning for root resource and provider classes in the packages:
    com.journaldev
    Jul 23, 2019 3:39:02 PM org.apache.catalina.core.ApplicationContext log
    SEVERE: StandardWrapper.Throwable
    java.lang.IllegalArgumentException
    at jersey.repackaged.org.objectweb.asm.ClassReader.(ClassReader.java:170)
    at jersey.repackaged.org.objectweb.asm.ClassReader.(ClassReader.java:153)
    at jersey.repackaged.org.objectweb.asm.ClassReader.(ClassReader.java:424)
    at com.sun.jersey.spi.scanning.AnnotationScannerListener.onProcess(AnnotationScannerListener.java:138)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner$1.f(FileSchemeScanner.java:86)
    at com.sun.jersey.core.util.Closing.f(Closing.java:71)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scanDirectory(FileSchemeScanner.java:83)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scanDirectory(FileSchemeScanner.java:80)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scanDirectory(FileSchemeScanner.java:80)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scan(FileSchemeScanner.java:71)
    at com.sun.jersey.core.spi.scanning.PackageNamesScanner.scan(PackageNamesScanner.java:226)
    at com.sun.jersey.core.spi.scanning.PackageNamesScanner.scan(PackageNamesScanner.java:142)
    at com.sun.jersey.api.core.ScanningResourceConfig.init(ScanningResourceConfig.java:80)
    at com.sun.jersey.api.core.PackagesResourceConfig.init(PackagesResourceConfig.java:104)
    at com.sun.jersey.api.core.PackagesResourceConfig.(PackagesResourceConfig.java:78)
    at com.sun.jersey.api.core.PackagesResourceConfig.(PackagesResourceConfig.java:89)
    at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:696)
    at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:674)
    at com.sun.jersey.spi.container.servlet.WebComponent.init(WebComponent.java:205)
    at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:394)
    at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:577)
    at javax.servlet.GenericServlet.init(GenericServlet.java:158)
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1132)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1079)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:973)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4885)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5199)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1412)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1402)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)

    Jul 23, 2019 3:39:02 PM org.apache.catalina.core.StandardContext loadOnStartup
    SEVERE: Servlet [Jersey REST Service] in web application [/JournaldevWebservice] threw load() exception
    java.lang.IllegalArgumentException
    at jersey.repackaged.org.objectweb.asm.ClassReader.(ClassReader.java:170)
    at jersey.repackaged.org.objectweb.asm.ClassReader.(ClassReader.java:153)
    at jersey.repackaged.org.objectweb.asm.ClassReader.(ClassReader.java:424)
    at com.sun.jersey.spi.scanning.AnnotationScannerListener.onProcess(AnnotationScannerListener.java:138)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner$1.f(FileSchemeScanner.java:86)
    at com.sun.jersey.core.util.Closing.f(Closing.java:71)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scanDirectory(FileSchemeScanner.java:83)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scanDirectory(FileSchemeScanner.java:80)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scanDirectory(FileSchemeScanner.java:80)
    at com.sun.jersey.core.spi.scanning.uri.FileSchemeScanner.scan(FileSchemeScanner.java:71)
    at com.sun.jersey.core.spi.scanning.PackageNamesScanner.scan(PackageNamesScanner.java:226)
    at com.sun.jersey.core.spi.scanning.PackageNamesScanner.scan(PackageNamesScanner.java:142)
    at com.sun.jersey.api.core.ScanningResourceConfig.init(ScanningResourceConfig.java:80)
    at com.sun.jersey.api.core.PackagesResourceConfig.init(PackagesResourceConfig.java:104)
    at com.sun.jersey.api.core.PackagesResourceConfig.(PackagesResourceConfig.java:78)
    at com.sun.jersey.api.core.PackagesResourceConfig.(PackagesResourceConfig.java:89)
    at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:696)
    at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:674)
    at com.sun.jersey.spi.container.servlet.WebComponent.init(WebComponent.java:205)
    at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:394)
    at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:577)
    at javax.servlet.GenericServlet.init(GenericServlet.java:158)
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1132)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1079)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:973)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4885)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5199)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1412)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1402)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)

    Any idea, what is wrong here?

  4. Ramakrishna says:

    I’m new to rest full and weblogic server. Can you please guide me how to deploy in weblogic 11gR1. I’m getting error 404,

  5. anupama says:

    Thank you for the tutorial. Initially I got an error related to permissions on Tomcat folder. Providing write permissions solved it

  6. Indranil Goswami says:

    Hi Pankaj ,
    Thanks for the tutorial very well explained . I have one question , when we hit getAll resource , then in response we are getting the collection of Person , but from where the root element is coming ?

    1. Gayatri says:

      Even I have same doubt.. Where is the root element people coming from???

      1. Raviraj says:

        I think the root element comes as default from the REST API, how i found out is i changed the @XmlRootElement (name=”person”) of person class to @XmlRootElement (name=”Employee”). Still we get the root element of this Employee element as (collection of person objects) only.

        1. Raviraj says:

          People root element

  7. Srikant Das says:

    While deploying the same application into Tomcat, I am getting the below error in server console. Kindly help me.

    Dec 13, 2018 9:12:40 AM org.apache.catalina.core.ContainerBase startInternal
    SEVERE: A child container failed during start
    java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/RestfulWebService]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:943)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:871)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

    1. Srikant Das says:

      Hello Pankaj,

      Could you pease suggest the solution for above issue. I am using java 8 and and tomcat 8 to run the application.

      Thanks,
      Srikant

      1. Pankaj says:

        I am not sure of the issue you are facing, it doesn’t seem to be related to the app. How are you generating the WAR file? Please generate using maven build and deploy it explicitly.

      2. pavani says:

        u have to use tomcat 9 for java8

  8. Navin says:

    Nice article, presize ,brief,overview of rest.
    Best for my kind of people who would first need to know overall flow,not like Spaghetti code and give up.

  9. Raashid says:

    What changes to make for getting JSON instead of XML in this project

  10. Kamalakar says:

    Thank you for writing this tutorial. Its very easy to understand.

  11. Carlos Herrera says:

    Hi,

    I just started my first software developer position and i’ve got to tell you – this tutorial really cleared up some ambiguity around a current project that was assigned to me . I had never seen or touched any kind of web services in Java. Reading this simple yet effective tutorial helped me better understand the structure of REST services using Java.

    – Carlos Herrera

  12. Next says:

    How come on getAll request we get …? I don’t get from where it comes?

  13. Rupam Singh says:

    Hello Pankaj !
    Your website is great . Thanks for the amazing work you have put in.
    For REST though I think having verbs in the @Path is not a good programming practice.
    For e.g. here – /person/add . The POST/PUT/GET/DELETE are the verbs that tell you what has to be done. They should not be part of the URI.
    I think adding a tutorial on best practices for REST will clarify & fix these naive mistakes !
    Thanks

    1. Pankaj says:

      Yes, I agree with your point, when I wrote the tutorial my aim was to create REST web services with least complexities so that a new user can easily understand and get started with it. I will write a tutorial on best practices for REST in a while.

  14. Randhir says:

    in case of add where to put value for name,id,age i m getting nyll pointer exception

  15. Krishnam Raju says:

    I am unable to run the application.

  16. Daniel says:

    Hi. I am having problem with this error in EasyRest. “java.lang.ClassNotFoundException: org.jboss.resteasy.plugins.server.servlet.HttpServletDistpatcher from [Module “deployment.JAXRS-Example-RestEasy-0.0.1-SNAPSHOT.war:main” from Service Module Loader]”. Can you help me?. Thanks.

  17. Charlotte says:

    Hi,

    I have some trouble understanding how client-server applications work with REST. Have I understood it correctly that this example is the server side code? How would the client side code look? Is it just code for making a GET request and parsing the response (doing whatever you want done with it)?

    I would be very thankful for a response, I am a bit confused by how I would develop a client-server application with REST and any clarifications would be really appreciated!

    1. Pankaj says:

      Yes, you are right. Client will make HTTP calls to server (GET, POST etc.) and receive response. It can be plain HTML, XML, JSON etc. Client is free to do whatever with it.

  18. Supriya says:

    To delete resource, use @DELETE annotation, but here @GET annoatation is used. Please explain.

    1. Pankaj says:

      You can use @DELETE also, ideally you should.

  19. myjaysan myjaysan says:

    https://stackoverflow.com/questions/46863773/jersey-client-maintain-state-cookies-sends-get-post-set-cookiesget-2nd

    0
    down vote
    favorite
    In Jersey Client, I want to maintain Cookies and using Cookies want to send GET requests second time, to fetch JSON data. Why is Set-cookies used? Do I need to maintain State or cookies?

    import javax.ws.rs.client.Client;
    import javax.ws.rs.client.ClientBuilder;
    import javax.ws.rs.client.Entity;
    import javax.ws.rs.client.WebTarget;
    import javax.ws.rs.core.MultivaluedHashMap;
    import javax.ws.rs.core.MultivaluedMap;
    import javax.ws.rs.core.Response;

    public class ExampleRestAPIClient {

    public static void main(String[] args) {

    Client client = ClientBuilder.newClient();
    WebTarget baseTarget =
    client.target(“https://shoaibapi.erpnext.com/api/method/login”);

    MultivaluedMap formData =
    new MultivaluedHashMap();
    formData.add(“usr”, “shoaibshaikh1516@gmail.com”);
    f ormData.add(“pwd”, “qweqwe”);
    Response response = baseTarget.request().post(Entity.form(formData));

    System.out.println(“\n postResponse which is send\n”);

    System.out.println(response);

    if (response.getStatus() != 201) {
    System.out.println(“Error”);
    }

    String createdMessage = response.readEntity(String.class);
    System.out.println(createdMessage);

    System.out.println(“\n\n”);
    System.out.println(response.getCookies());
    }
    }

  20. Tejas Gowda says:

    I pasted war file in webapps directory and restarted server, but i get 404. Plz suggest pankaj sir

    1. Pankaj says:

      What is the WAR file name and the unzipped directory created? Usually in Tomcat that is the context of the webapp. So if WAR file name is “abc.war” and folder got created is “abc” then try to access the webapp at localhost:8080/abc for homepage.

      1. Krishnam Raju says:

        I am also having the same problem. Still getting 404 error.

      2. Krishna says:

        I faced the same issue and I was able to get it working
        you may not be able to access through browser using webApp name as contextRoot, mostly I believe due to no welcome servlet defined.
        However you provide the webApp(war file name) in postman requests instead of display name in web.xml
        postman request should look like below to work for you
        http://localhost:8080/abc/person/add (assuming your war file is abc, it does not work with the defined in web.xml)
        hope this helps

  21. Tejaswini K says:

    Hi,

    I’m having problem with Maven, while creating maven project getting an error for pom.xml file like (
    Cannot read lifecycle mapping metadata for artifact org.apache.maven.plugins:maven-clean-plugin:maven-plugin:2.5:runtime Cause: error in opening zip file pom.xml ) but in my system i have done proper installation for maven.
    I tried many ways to clear this error still no use please suggest me how can I clear this.

    1. Sunil says:

      Check your internet connection as Maven needs to download artifacts. Also, make sure your settings.xml is correct.

  22. cs says:

    Hi Pankaj,
    Thanks for the great tutorial.
    I have one question.
    Am I right in thinking that, if there was an updatePesrson method, then the code would become non-thread safe.
    So in that case is it suggested to use ConcurrentHaspMap to store the data?
    What are your thoughts?
    Thank You.

    1. Pankaj says:

      Yes, but in most of the cases you will store data into Database where you can set auto commit false and use transaction management.

  23. Aparna says:

    Great Article . Well Explained !!!!

  24. Houssamel-din says:

    Great article

  25. S COULIBALY says:

    Hi your post method is NOT very clear to me , could you explain to me how will I invoke Add method I see it is a Http post But how will I invoke this path CANNOT be in browser , do you I need to create a separate Client with Main method ?

  26. Savani Fu says:

    Hello Pankaj,

    Could you please provide link to download source code? I don’t see it on this page. Please help.

    Regards,
    Savani

    1. Pankaj says:

      This is because most of the code is given and it’s simple. I would say create yourself for better learning.

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