Spring REST XML Example

In this tutorial, I am writing hello world example for RESTful APIs using Spring REST features. In this example, I will be creating two APIs which will return XML representation of resources.

Maven Dependencies

Let’s start with runtime dependencies which you will need to write these RESTFul APIs. In fact, all you need is Spring MVC support only.

POM.xml

Note: If you please planning to include JSON support as well then all you need to do is include Jackson libraries into classpath, and same APIs will work for jackson as well.

<dependency>     <groupId>com.fasterxml.jackson.core</groupId>     <artifactId>jackson-databind</artifactId>     <version>2.4.1</version> </dependency>

Spring MVC Configuration

For creating APIs, you will need to configure your applications

web.xml

<!DOCTYPE web-app PUBLIC  "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"  "http://java.sun.com/dtd/web-app_2_3.dtd" >  <web-app>   <display-name>Archetype Created Web Application</display-name>    <servlet>         <servlet-name>spring</servlet-name>             <servlet-class>                 org.springframework.web.servlet.DispatcherServlet             </servlet-class>         <load-on-startup>1</load-on-startup>     </servlet>     <servlet-mapping>         <servlet-name>spring</servlet-name>         <url-pattern>/</url-pattern>     </servlet-mapping> </web-app>

spring-servlet.xml

xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:context="http://www.springframework.org/schema/context"

xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:p="http://www.springframework.org/schema/p"

xsi:schemaLocation="

http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-4.1.xsd

http://www.springframework.org/schema/context

http://www.springframework.org/schema/context/spring-context-4.1.xsd

http://www.springframework.org/schema/mvc

http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">

        

    <context:component-scan base-package="com.accenture" />

    <mvc:annotation-driven />

</beans>

JAXB Annotated Model Objects

You will need to annotate your model objects with jaxb annotations so that JAXB can marshal the java object into XML representation to be sent to client for that API.

EmployeeVO.java

import java.io.Serializable;

import javax.xml.bind.annotation.XmlAccessType;

import javax.xml.bind.annotation.XmlAccessorType;

import javax.xml.bind.annotation.XmlAttribute;

import javax.xml.bind.annotation.XmlElement;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement (name = "employee")

@XmlAccessorType(XmlAccessType.NONE)

public class EmployeeVO implements Serializable

{

    private static final long serialVersionUID = 1L;

    @XmlAttribute

    private Integer id;

    

    @XmlElement

    private String firstName;

    

    @XmlElement

    private String lastName;

    

    @XmlElement

    private String email;

    

    public EmployeeVO(Integer id, String firstName, String lastName, String email) {

        super();

        this.id = id;

        this.firstName = firstName;

        this.lastName = lastName;

        this.email = email;

    }

    

    public EmployeeVO(){

        

    }

    //Setters and Getters

    @Override

    public String toString() {

        return "EmployeeVO [id=" + id + ", firstName=" + firstName

                + ", lastName=" + lastName + ", email=" + email + "]";

    }

}

EmployeeListVO.java

import java.util.ArrayList;

import java.util.List;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement (name="employees")

public class EmployeeListVO implements Serializable

{

    private static final long serialVersionUID = 1L;

    

    private List employees = new ArrayList();

    public List getEmployees() {

        return employees;

    }

    public void setEmployees(List employees) {

        this.employees = employees;

    }

}

REST Controller

This is main class which will decide that which API will behave which way.

EmployeeRESTController.java

import org.springframework.http.HttpStatus;

import org.springframework.http.ResponseEntity;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.ResponseBody;

import org.springframework.web.bind.annotation.RestController;

import com.howtodoinjava.demo.model.EmployeeListVO;

import com.howtodoinjava.demo.model.EmployeeVO;

@RestController

public class EmployeeRESTController

{

    @RequestMapping(value = "/employees")

    public EmployeeListVO getAllEmployees()

    {

        EmployeeListVO employees = new EmployeeListVO();

        

        EmployeeVO empOne = new EmployeeVO(1,"Naresh","C","nareshc@gmail.com");

        EmployeeVO empTwo = new EmployeeVO(2,"Anil","B","anilb@yahoo.com");

        EmployeeVO empThree = new EmployeeVO(3,"krish","J","krishj@gmail.com");

        employees.getEmployees().add(empOne);

        employees.getEmployees().add(empTwo);

        employees.getEmployees().add(empThree);

        

        return employees;

    }

    

    @RequestMapping(value = "/employees/{id}")

    public ResponseEntity getEmployeeById (@PathVariable("id") int id)

    {

        if (id <= 3) {

            EmployeeVO employee = new EmployeeVO(1,"Naresh","C","nareshc@gmail.com");

            return new ResponseEntity(employee, HttpStatus.OK);

        }

        return new ResponseEntity(HttpStatus.NOT_FOUND);

    }

}

Let’s note down few important things.

1) We have used @RestController annotation. Till Spring 3, we would have been using @Controller annotation and in that case it was important to use@ResponseBody annotation as well. e.g.

@Controller public class EmployeeRESTController {     @RequestMapping(value = "/employees")     public @ResponseBody EmployeeListVO getAllEmployees()     {         //API code     } }

Spring 4 introduced @RestController which is combination of @Controller + @ResponseBody. So when using @RestController, you do not need to use@ResponseBody. It’s optional.

2) Here we are relying on the Spring MVC HttpMessageConverters to convert an object to the xml representation requested by the user. @ResponseBody annotation (included through @RestController) tells Spring MVC that the result of the method should be used as the body of the response. As we want XML this marshaling is done by the Jaxb2RootElementHttpMessageConverter provided by Spring which is automatically registered in spring context if JAXB libraries are found in classpath. As I am using JRE 7 to run this application and it has JAXB inbuilt, so I do not need to add external dependency through maven.

3) Due to the @ResponseBody annotation, we don’t need the view name anymore but can simply return the employees object.

4) Instead of returning the java objects directly, you can wrap them insideResponseEntity. The ResponseEntity is a class in Spring MVC that acts as a wrapper for an object to be used as the body of the result together with a HTTP status code. This provides greater control over what you are returning to client in various use cases. e.g. returning a 404 error if no employee is found for given employee id.

Test the APIs

Let’s test above REST APIs.

1) Hit URL : http://localhost:8080/springrestexample/employees

You can pass accept header “application/xml” as well.