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Spring MVC hello world example

May 23, 2012 , ,

Spring 3
You may interest at this Spring 3 MVC hello world example.
In Spring MVC web application, it consist of 3 standard MVC (Model, Views, Controllers) components :
  1. Models – Domain objects that are processed by service layer (business logic) or persistent layer (database operation).
  2. Views – Usually JSP page written with Java Standard Tag Library (JSTL).
  3. Controllers – Interact with service layer for business processing and return a Model.
See following figures 1.1, 1.2 to demonstrate how Spring MVC web application handle a web request.
Figure 1.1 – Image copied from Spring MVC reference with slightly modification.
spring mvc concepts
Figure 1.2 – P.S Image copied from book : Spring Recipes
spring-mvc-concepts-2
Note
In Spring MVC , the core disatcher component is the “DispatcherServlet“, which act as the front-controller (design pattern). Every web request have to go through this “DispatcherServlet“, and the “DispatcherServlet” will dispatches the web request to suitable handlers.

Spring MVC Tutorial

In this tutorial, you will create a simple Spring MVC hello world web application in order to understand the basic concepts and configurations of this framework.
Technologies used in this tutorial.
  1. Spring 2.5.6
  2. JDK 1.6
  3. Eclipse 3.6
  4. Maven 3

1. Directory Structure

Final directory structure of this tutorial.
spring mvc hello world directory structure

2. Dependency library

Spring MVC required two core dependency libraries, spring-version.jar and spring-mvc-version.jar. If you are using JSP page with jstl, include the jstl.jar and standard.jar as well.
File : pom.xml
        
	
		org.springframework
		spring
		2.5.6
	
 
         
	
		org.springframework
		spring-webmvc
		2.5.6
	
 
	 
	
		javax.servlet
		jstl
		1.1.2
	
 
	
		taglibs
		standard
		1.1.2
	
 
	
	
		javax.servlet
		servlet-api
		2.5
		provided

3. Spring Controller

Spring comes with many Controllers, normally, you just need to extend the AbstractController, if you do not have other special requirement, and override the handleRequestInternal() method and return a ModelAndViewobject.
File : HelloWorldController.java
package com.mkyong.common.controller;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;
 
public class HelloWorldController extends AbstractController{
 
	@Override
	protected ModelAndView handleRequestInternal(HttpServletRequest request,
		HttpServletResponse response) throws Exception {
 
		ModelAndView model = new ModelAndView("HelloWorldPage");
		model.addObject("msg", "hello world");
 
		return model;
	}
}
  1. ModelAndView(“HelloWorldPage”) – The “HelloWorldPage” will pass to Spring’s viewResolver later, to indentify which view should return back to the user. (see step 6)
  2. model.addObject(“msg”, “hello world”) – Add a “hello world” string into a model named “msg”, later you can use JSP EL ${msg} to display the “hello world” string.

4. View (JSP page)

In this case, “view” is a jSP page, you can display the value “hello world” that is store in the model “msg” via expression language (EL) ${msg}.
File : HelloWorldPage.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<body>
	<h1>Spring MVC Hello World Example</h1>
 
	<h2>${msg}</h2>
 
</body>
</html>
Note 
If the ${msg} is displayed as it is, not the value inside the “msg” model, it may caused by the old JSP 1.2 descriptor, which make the expression languages disabled by default, see the solution here.

5. Spring Configuration

In web.xml, declared a DispatcherServlet servlet, named “mvc-dispatcher“, and act as the front-controller to handle all the entire web request which end with “htm” extension.
File : web.xml
 id="WebApp_ID" version="2.4" 
	xmlns="http://java.sun.com/xml/ns/j2ee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 
  Spring Web MVC Application
 
  
  	mvc-dispatcher
        
                  org.springframework.web.servlet.DispatcherServlet
        
        1
  
 
  
 	mvc-dispatcher
        *.htm
  
 
Note 
The DispatcherServlet name “mvc-dispatcher“, is used to defined which file to load the Spring MVC configurations. By default, it will look for file by joining the servlet name “mvc-dispatcher” with “-servlet.xml” as the file name, in this case, it will find the “mvc-dispatcher-servlet.xml” file and load the Spring MVC configuration.
Alternatively, you can explicitly specify the Spring configuration file in the “contextConfigLocation” servlet parameter, to ask Spring to load your configurations besides the default “mvc-dispatcher-servlet.xml“.
File : web.xml
 id="WebApp_ID" version="2.4" 
	xmlns="http://java.sun.com/xml/ns/j2ee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 
  Spring Web MVC Application
 
  
  	mvc-dispatcher
        
               org.springframework.web.servlet.DispatcherServlet
        
        1
  
 
  
 	mvc-dispatcher
        *.htm
  
 
  
	contextConfigLocation
	/WEB-INF/SpringMVCBeans.xml
  
 
  
        
		org.springframework.web.context.ContextLoaderListener
        
  
 

6. Spring Beans Configuration

Declared the Spring Controller and viewResolver.
File : mvc-dispatcher-servlet.xml
 xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 
	http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 
     name="/welcome.htm" 
	class="com.mkyong.common.controller.HelloWorldController" />
 
     id="viewResolver"
    	class="org.springframework.web.servlet.view.InternalResourceViewResolver" >
         name="prefix">
            /WEB-INF/pages/
        
         name="suffix">
            .jsp
        
    
 
  1. Controller – Declared a bean name “/welcome.htm” and map it to HelloWorldController class. It means, if an URL with “/welcome.htm” pattern is requested, it will send to the HelloWorldController controller to handle the request.
  2. viewResolver – Define how Spring will looking for the view template. In this case, the controller “HelloWorldController” will return a ModelAndView object named “HelloWorldPage”, and the viewResolver will find the file with following mechanism : “prefix + ModelAndView name + suffix“, which is “/WEB-INF/pages/HelloWorldPage.jsp“.
Note
Actually, you don’t need to define the BeanNameUrlHandlerMapping in the web.xml, by default, if no handler mapping can be found, the DispatcherServlet will creates a BeanNameUrlHandlerMapping automatically. See this article – BeanNameUrlHandlerMapping example for detail.

7. Demo

Run it and access via URL : http://localhost:8080/SpringMVC/welcome.htm , the “SpringMVC” is your project context name.
spring mvc demo
How it works?
  1. http://localhost:8080/SpringMVC/welcome.htm is requested.
  2. URL is end with “.htm” extension, so it will redirect to “DispatcherServlet” and send request to the default BeanNameUrlHandlerMapping.
  3. BeanNameUrlHandlerMapping return HelloWorldController to the DispatcherServlet.
  4. DispatcherServlet forward request to the HelloWorldController.
  5. HelloWorldController process it and return a ModelAndView object named “HelloWorldPage”.
  6. DispatcherServlet received the ModelAndView and call the viewResolver to process it.
  7. viewResolver return the “/WEB-INF/pages/HelloWorldPage.jsp” back to the DispatcherServlet.
  8. DispatcherServlet return the “HelloWorldPage.jsp” back to user.
Spring MVC in annotation
You may interest at this Spring MVC hello world annotation example.

Download Source Code

Download it – SpringMVC-Hello-World-Example-XML.zip (7KB)

Reference

  1. Spring MVC documentation

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