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In this example, we will learn how to develop a simple Jersey Rest hello world example.

JAX-RS Specification is the Java API for RESTful web services. Jersey is the open source reference implementation of Java JAX-RS specification. It provides a Java library using which we can easily create RESTful web services in Java platform. JAX-RS / Jersey supports JAXB based XML bindings as well.

Technologies and tools used

Jersey 2.27
JDK 1.8
Tomcat 8.5
Maven 3.0.3
Eclipse Neon

In this tutorial, we have used the latest Jersey version 2.27 with JDK 8. Deployment of a JAX-RS application using @ApplicationPath with Servlet 3.0 ( use @ApplicationPath("resources") annotation to configure Jersey Servlet Container).

Development Steps

Create Maven Web Application Project
Project Packaging Structure
Update Jersey Dependencies in a Pom.Xml File
Create Resource - HelloWorldResource.java
Descriptor-Less Deployment Configuration
Build and Deployment
Conclusion

1. Create a Maven Web Application Project

Use How to Create a Web Project Using Maven in Eclipse - In this article, we will show you how to create a web project or application using maven in Eclipse IDE.

2. Project Packaging Structure

In a typical Jersey application, the project packaging structure may look:

3. Update Jersey Dependencies in a 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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.javadevelopersguide.jersey</groupId>
    <artifactId>jersey-helloworld-example</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>jersey-helloworld-example Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.core</groupId>
            <artifactId>jersey-server</artifactId>
            <version>2.7</version>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
            <version>2.7</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>jersey-helloworld-example</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.0.2</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
            </plugin>
        </plugins>
    </build>
</project>

4. Create Resource - HelloWorldResource.java

package com.javadevelopersguide.jersey.helloworld;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

@Path("/")
public class HelloWorldResource {

    @GET
    @Path("helloworld")
    public String helloworld() {
        return "Helloworld !!!!";
    }
}

5. Descriptor-Less Deployment Configuration

Here are multiple deployment options in the Servlet 3.0 container for a JAX-RS application defined by implementing a custom Application subclass. For simple deployments, no web.xml is necessary at all.

Instead, an @ApplicationPath annotation can be used to annotate the custom Application subclass and define the base application URI for all JAX-RS resources configured in the application:

package com.javadevelopersguide.jersey.config;

import javax.ws.rs.ApplicationPath;

import org.glassfish.jersey.server.ResourceConfig;

@ApplicationPath("resources")
public class MyApplication extends ResourceConfig {
    public JerseyServletContainerConfig() {
        // if there are more than two packanges then separate them with semicolon
        // exmaple : packages("org.foo.rest;org.bar.rest");
        packages("com.javadevelopersguide.jersey.helloworld");
    }
}

6. Build and Deployment

Let's build this maven project using the following maven command:

mvn clean install

Or, you can build from Eclipse IDE - Right click on a project -> Run As -> Maven Build and enter below command in the wizard:

clean install

Once, build successful, then deploy this project in apache tomcat server 8.5. Once the application is up and running, type http://localhost:8080/jersey-helloworld-example/ link in a browser will show below output:

7. Conclusion

This guide illustrated how to implement a simple hello world example using the latest jersey rest 2.27 and ResourceConfig @ApplicationPath annotation based configuration.

All the code of this article is available over on Github. This is a Maven-based project, so it should be easy to import and run as it is.

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