RESTful Web Service (JAX-RS) JSON Example Using Jersey

This article describes how to get a JSON response from the RESTful web services using jersey implementation.  Jersey will use Jackson to convert Java objects to/form JSON, but just don’t ask me what is Jackson 🙂 ,as of now just remember its a high performance JSON processor, Jersey will use this API to the marshaling [converting the objects] process. Check this link if you would like to know more about Jackson.

These steps are mandatory in order to make Jersey to support with JSON mappings.

• Apart from existing dependencies, add ‘jersey-json.jar‘ to your Maven pom.xml which includes all Jackson and other JSON supporting libraries

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

• In web.xml add “com.sun.jersey.api.json.POJOMappingFeature” as “init-param”
• In the web service class, we need to annotate the method with @Produces(MediaType.APPLICATION_JSON). By doing so we are instructiong the service method that we are expecting the JSON output, thats it jersey will take care rest of the things

Note: In previous examples i used Tomcat 6 and JDK 1.6 but for this [JAX-RS JSON Example] example i have used JDK 1.7.

Required Files

• pom.xml
• web.xml
• Customer.java
• JsonFromRestful.java

pom.xml

<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>JsonFromRestfulWebServices</groupId>
  <artifactId>JsonFromRestfulWebServices</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
 
    <repositories>
           <repository>
             <id>maven2-repository.java.net</id>
              <name>Java.net Repository for Maven</name>
              <url>http://download.java.net/maven/2/</url>
              <layout>default</layout>
           </repository>
    </repositories>
 
    <dependencies>
           <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.8.2</version>
                <scope>test</scope>
           </dependency>
    
           <dependency>
                <groupId>com.sun.jersey</groupId>
                <artifactId>jersey-server</artifactId>
                <version>1.8</version>
           </dependency>
           
           <dependency>
                <groupId>com.sun.jersey</groupId>
                <artifactId>jersey-json</artifactId>
                <version>1.8</version>
          </dependency>    
     </dependencies>
 
    <build>
       <finalName>JsonFromRestfulWebServices</finalName>
       <plugins>
          <plugin>
              <artifactId>maven-compiler-plugin</artifactId>
                 <configuration>
                    <compilerVersion>1.5</compilerVersion>
                    <source>1.5</source>
                    <target>1.5</target>
                 </configuration>
           </plugin>
       </plugins>
    </build>
</project>

 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/j2ee" xmlns:javaee="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" id="WebApp_ID" version="2.4">
  <display-name>JsonFromRestfulWebServices</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>java4s</param-value>
        </init-param>
        <init-param>
          <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
          <param-value>true</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>

 Customer.java

package java4s;

public class Customer {
    
    private int custNo;
    private String custName;
    private String custCountry;
    
    public int getCustNo() {
        return custNo;
    }
    public void setCustNo(int custNo) {
        this.custNo = custNo;
    }
    public String getCustName() {
        return custName;
    }
    public void setCustName(String custName) {
        this.custName = custName;
    }
    public String getCustCountry() {
        return custCountry;
    }
    public void setCustCountry(String custCountry) {
        this.custCountry = custCountry;
    }    
}

JsonFromRestful.java

package java4s;

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("/customers")
public class JsonFromRestful {
    
    @GET
    @Path("/{cusNo}")
    @Produces(MediaType.APPLICATION_JSON)
    public Customer produceCustomerDetailsinJSON(@PathParam("cusNo") int no) {

        /*
         * I AM PASSING CUST.NO AS AN INPUT, SO WRITE SOME BACKEND RELATED STUFF AND
         * FIND THE CUSTOMER DETAILS WITH THAT ID. AND FINALLY SET THOSE RETRIEVED VALUES TO
         * THE CUSTOMER OBJECT AND RETURN IT, HOWEVER IT WILL RETURN IN JSON FORMAT :-)
         * */
        
        Customer cust = new Customer();        
            cust .setCustNo(no);
            cust .setCustName("Java4s");
            cust .setCustCountry("India");
        return cust;
    }
}

Output

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.