How to write RESTful web services using spring mvc

<beans xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:p="http://www.springframework.org/schema/p" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemalocation="
 http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
 http://www.springframework.org/schema/context
 http://www.springframework.org/schema/context/spring-context-3.0.xsd
 http://www.springframework.org/schema/mvc
 http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

   <mvc:annotation-driven></mvc:annotation-driven>
 
   <context:component-scan base-package="com.dineshonjava.web">
   </context:component-scan>

  <bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
     <property name="mediaTypes">
       <map>
   <entry key="html" value="text/html"></entry>
   <entry key="json" value="application/json"></entry>
   <entry key="xml" value="application/xml"></entry>
 </map>
     </property>
     <property name="viewResolvers">
 <list>
  <bean class="org.springframework.web.servlet.view.UrlBasedViewResolver">
    <property name="viewClass" value="org.springframework.web.servlet.view.JstlView">
            </property>
     <property name="prefix" value="/WEB-INF/views/"></property>
     <property name="suffix" value=".jsp"></property>
   </bean>
 </list>
     </property>
  </bean>
</beans>

Step 3: Add model classes: There are two model classes Employee.java and Employees.java
These classes will be having JAXB annotations, which will be used by marshaller to convert them in appropriate xml or json formats.
Employees.java

package com.dineshonjava.web.model;

import java.util.Collection;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

/**
 * @author Dinesh Rajput
 *
 */
@XmlRootElement(name="employees")
@XmlAccessorType(XmlAccessType.NONE)
public class Employees {
 @XmlElement(name="employee")
 private Collection<Employee> employees;

 public Collection<Employee> getEmployees() {
  return employees;
 }

 public void setEmployees(Collection<Employee> employees) {
  this.employees = employees;
 }
}

Now write Employee.java

package com.dineshonjava.web.model;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

/**
 * @author Dinesh Rajput
 *
 */
@XmlRootElement(name="employees")
@XmlAccessorType(XmlAccessType.NONE)
public class Employee {
 @XmlElement(name="empId")
 private Integer id;
 @XmlElement(name="empName")
 private String name;
 @XmlElement(name="empAge")
 private Integer age;
 @XmlElement(name="empSalary")
 private Long salary;
 @XmlElement(name="empAddress")
 private String address;
 public Integer getId() {
  return id;
 }
 public void setId(Integer id) {
  this.id = id;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public Integer getAge() {
  return age;
 }
 public void setAge(Integer age) {
  this.age = age;
 }
 public Long getSalary() {
  return salary;
 }
 public void setSalary(Long salary) {
  this.salary = salary;
 }
 public String getAddress() {
  return address;
 }
 public void setAddress(String address) {
  this.address = address;
 }
}

Step 4: Write the controller - WebServiceController.java
Our WebServiceController.java will created to have REST specific annotations for path mappings in request parameters mappings. Also, we will specify the header attributes for request and response.

package com.dineshonjava.web.controller;

import java.util.ArrayList;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import com.dineshonjava.web.model.Employee;
import com.dineshonjava.web.model.Employees;

/**
 * @author Dinesh Rajput
 *
 */
@Controller
@RequestMapping("/employees")
public class WebServiceController {
 
 @RequestMapping(method = RequestMethod.GET, value="/{id}", headers="Accept=*/*")
 public @ResponseBody Employee getEmployeeById(@PathVariable String id){
  Employee employee = new Employee();
  employee.setId(1);
  employee.setSalary(50000l);
  employee.setName("Dinesh Rajput");
  employee.setAge(26);
  employee.setAddress("Sector 49-Noida");
  return employee;
 }
 
 @RequestMapping(method = RequestMethod.GET,  headers="Accept=*/*")
 public @ResponseBody Employees getEmployees(){
  Employees employees = new Employees();
  
  Employee employee1 = new Employee();
  employee1.setId(2);
  employee1.setSalary(50000l);
  employee1.setName("Dinesh Rajput");
  employee1.setAge(26);
  employee1.setAddress("Sector 49- Noida");
  
  Employee employee2 = new Employee();
  employee2.setId(3);
  employee2.setSalary(20000l);
  employee2.setName("Anamika Rajput");
  employee2.setAge(26);
  employee2.setAddress("Sector 49- Noida");
  employees.setEmployees(new ArrayList<Employee>());
  employees.getEmployees().add(employee1);
  employees.getEmployees().add(employee2);
  return employees;
 }
}

web.xml

<web-app version="2.5" 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_2_5.xsd">

 <servlet>
    <servlet-name>sdnext</servlet-name>
    <servlet-class>
               org.springframework.web.servlet.DispatcherServlet
            </servlet-class>
  <init-param>
            <param-name>contextConfigLocation</param-name><param-value>/WEB-INF/config/sdnext-servlet.xml</param-value></init-param>
        <load-on-startup>1</load-on-startup>
 </servlet>

 <servlet-mapping>
  <servlet-name>sdnext</servlet-name>
  <url-pattern>*.html</url-pattern>
 </servlet-mapping>

 <welcome-file-list>
  <welcome-file>index.html</welcome-file>
 </welcome-file-list>
</web-app>

Now lets deploy the application on tomcat and hit the URL on any REST client. I am using RESTClient. This is a firefox plugin for testing the RESTful webservices.

Using URL: http://localhost:8080/sdnext/employees/3.html
Now see the following result-