8632. Creating RESTful Web Services with Jersey
Jersey, RESTful, and Maven

Build RESTful web services with Jersey in Java.

1. Jersey

Jersey RESTful Web Services framework is an open source framework for developing RESTful Web Services in Java. It provides support for JAX-RS APIs and serves as a JAX-RS Reference Implementation.

2. Jersey Project

2.1 Creating Maven Project

1) In Eclipse, New -> ‘Dynamic Web Project’, Name: JerseyTutorial
2) Right click project JerseyTutorial -> Configure -> Convert to Maven Project. You should see a new file pom.xml under the root of project.

2.2 Adding Dependency

Add jersey dependency to pom.xml.

<dependencies>
    ...

    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-server</artifactId>
        <version>1.8</version>
    </dependency>
</dependencies>

2.3 Adding web.xml to project

Right click on project JerseyTutorial -> Java EE Tools -> Generate Deployment Descriptor Stub. You should see web.xml in /JerseyTutorial/WebContent/WEB-INF/.
Register Jersey service as follows.

<?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" version="3.0">
  <display-name>JerseyTutorial</display-name>
  <servlet>
      <servlet-name>jersey-serlvet</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>Johnny.Tutorials</param-value>
      </init-param>
      <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
      <servlet-name>jersey-serlvet</servlet-name>
      <url-pattern>/rest/*</url-pattern>
  </servlet-mapping>
</web-app>

2.4 Creating Jersey Service

1) Create Package
Right click on project JerseyTutorial -> New -> Package, Package Name: Johnny.Tutorials
2) Create class Product and ProductDao
Product.java

package Johnny.Tutorials;

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 int id;
    private String name;
    private double price;

    public Product() {}

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

    public int getId() {
        return id;
    }
    @XmlElement
    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }
    @XmlElement
    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }
    @XmlElement
    public void setPrice(double price) {
        this.price = price;
    }
}

ProductDao.java
Here, we create some dummy data.

package Johnny.Tutorials;

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

public class ProductDao {
    Map<Integer, Product> map = new HashMap<Integer, Product>();
    public List<Product> getAllProducts(){
        if (map == null || map.size() == 0) {
            buildProductList();
        }
        return new ArrayList<Product>(map.values());
    }

    public Product getProduct(int id){
        if (map == null || map.size() == 0) {
            buildProductList();
        }
        return map.get(id);
    }

    private void buildProductList() {
        Product product = new Product(1, "iPhone 7s", 700.00);
        map.put(1, product);
        product = new Product(2, "iPad 4", 500.00);
        map.put(2, product);
        product = new Product(3, "iPod", 300.00);
        map.put(3, product);
    }
}

ProductService.java
We use Jersey to create two APIs, one to get product list, another to get product by Id.

package Johnny.Tutorials;

import java.util.List;

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

@Path("/ProductService")
public class ProductService {
    ProductDao dao = new ProductDao();

    //Sample URL: http://localhost:8080/JerseyTutorial/rest/ProductService/products
    @GET
    @Path("/products")
    public List<Product> getAll() {
        return dao.getAllProducts();
    }

    //Sample URL: http://localhost:8080/JerseyTutorial/rest/ProductService/product/1
    @GET
    @Path("/product/{id}")
    public Product getProduct(@PathParam("id") int id) {
        return dao.getProduct(id);
    }
}

2.5 Project Structure

This is the final structure of this tutorial project. image

2.6 Running and Testing

1) Right click project JerseyTutorial -> Run As -> Run On Server.
Choose an existing server or create a new Tomcat server.
image

After Tomcat is started, let’s test RESTful services through web browser.
2) Get Product List

  • http://localhost:8080/JerseyTutorial/rest/ProductService/products

image
3) Get Product by ID

  • http://localhost:8080/JerseyTutorial/rest/ProductService/product/1

image

3. Supporting Json

3.1 Adding Dependency to pom.xml

<dependencies>
    ...

    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-json</artifactId>
        <version>1.8</version>
    </dependency>
</dependencies>

3.2 Adding init param to web.xml

<servlet>
    ...

    <init-param>
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
    </init-param>
    ...
</servlet>

3.3 Adding new API to ProductService

In ProductService.java, add the following method.

@GET
@Path("/productJson/{id}")
@Produces(MediaType.APPLICATION_JSON)
public Product getProductJson(@PathParam("id") int id) {
    return dao.getProduct(id);
}

3.4 Testing Json API

Get product by id, data is returned in JSON format.

  • http://localhost:8080/JerseyTutorial/rest/ProductService/productJson/1

image

4. Source Files

5. Reference