JSON Response from the RESTful Web Services

Overview

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.Jackson ObjectMapper can parse JSON from a string, stream or file, and create a Java object or object graph representing the parsed JSON.Jersey will use this API to the marshaling [converting the objects] process.

Add ‘jersey-json.jar‘ to your Maven pom.xml which includes all Jackson and other JSON supporting libraries.

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>RESTExceptionHandlingExample</groupId>
  <artifactId>RESTExceptionHandlingExample</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  <name>WebServicesJAXRS</name>
  <description>Restfull Webservices</description>
  <dependencies>		
		<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>
    <sourceDirectory>RESTExceptionHandlingExample</sourceDirectory>
    <plugins>
      <plugin>
        <artifactId>maven-war-plugin</artifactId>
        <version>2.3</version>
        <configuration>
          <warSourceDirectory>WebContent</warSourceDirectory>
          <failOnMissingWebXml>false</failOnMissingWebXml>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

<groupId>RESTExceptionHandlingExample</groupId>

<artifactId>RESTExceptionHandlingExample</artifactId>

<version>0.0.1-SNAPSHOT</version>

<name>WebServicesJAXRS</name>

<description>Restfull Webservices</description>

<groupId>com.sun.jersey</groupId>

<artifactId>jersey-server</artifactId>

</dependency>

<groupId>com.sun.jersey</groupId>

<artifactId>jersey-json</artifactId>

</dependency>

</dependencies>

<build>

<sourceDirectory>RESTExceptionHandlingExample</sourceDirectory>

<artifactId>maven-war-plugin</artifactId>

<warSourceDirectory>WebContent</warSourceDirectory>

<failOnMissingWebXml>false</failOnMissingWebXml>

</configuration>

</plugin>

</plugins>

</build>

</project>

In web.xml add “com.sun.jersey.api.json.POJOMappingFeature” as “init-param”

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">  
 <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.codenuclear</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 REST Service</servlet-name>  
    <url-pattern>/rest/*</url-pattern>  
  </servlet-mapping>
    
</web-app>

<?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">

<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.codenuclear</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 REST Service</servlet-name>

<url-pattern>/rest/*</url-pattern>

</servlet-mapping>

</web-app>

Customer.java


package com.codenuclear;

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;
	}
        
}

package com.codenuclear;

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;

}

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.

JsonFromRestful.java


package com.codenuclear;

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("/users")
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("codeNuclear");
            cust .setCustCountry("India");
            return cust;
    }
	
}