Welcome to Spring MVC.

The purpose of this tutorial is not just to get started with a spring mvc project but also have a clear understanding of its elements and their relevance.

Spring MVC is an implementation of MVC pattern using Front controller design pattern.

The front controller named ‘DispatcherServlet’ implementation is provided by spring framework and it redirects request to appropriate controllers configured in spring xml config or using annotations.

I personally prefer to use annotation based controllers as they provide a cleaner solution with the details inside the java files itself.

We will configure our project using eclipse and maven instead of STS so that the configuration will involve manual steps helpful in remembering the steps as well.:)

First click on File>New>Maven Projects

Then on the next screen to create a simple project (skip archetypes).

On next screen fill project structure details and click Finish:

Modify pom.xml to add following dependencies:

  4.0.0
  springaddon
  apring-mvc-basic
  0.0.1-SNAPSHOT
war
  com.springaddon.springmvc
  Spring MVC Project

    
	        
	            com.springsource.repository.bundles.release
	            EBR Spring Release Repository
	            http://repository.springsource.com/maven/bundles/release
	        
	        
	            com.springsource.repository.bundles.external
	            EBR External Release Repository
	            http://repository.springsource.com/maven/bundles/external
	        
	         
        java.net-m2
        java.net - Maven 2
        https://repository.jboss.org/nexus/content/repositories/java.net-m2
      
	    

	

		3.1.0.RELEASE
		1.2
	

	
	
			javax.servlet
			jstl
			${jstl.version}
		
		
			org.springframework
			spring-core
			${org.springframework.version}
		
		
			org.springframework
			spring-webmvc
			${org.springframework.version}
		
		
			javax.servlet
			servlet-api
			2.5
			provided
		

	
	
		springMVCBasic
	

Once the project is created then add inside webapp/WEB-INF/web.xml

	
	
contextConfigLocation
classpath:servlet-context.xml
	

	

org.springframework.web.context.ContextLoaderListener
	
	
	
		springaddon
		org.springframework.web.servlet.DispatcherServlet
		
contextConfigLocation
classpath:servlet-context.xml
		
		1
	
	
		springaddon
		*.htm
	
	
		/WEB-INF/jsp/index.jsp
	

Below is a small description of web.xml elements:
This is the location of application context which the spring container will load for all its servlets and filters

contextConfigLocation
classpath:servlet-context.xml
	

Spring framework looks for a dispatcherservlet-servlet in our case springaddon-servlet.xml in the classpath but we can always override this behavior by providing an init-param named contextConfigLocation.

contextConfigLocation
classpath:servlet-context.xml

Then finally we need to add an entry for a listener to load the Spring container(application context)for all servlets and filters(in our case dispatcher servlet loader is also same):

  org.springframework.web.context.ContextLoaderListener

Now we will add the spring container named servlet-context in the classpath i.e. inside the resource folder.

Below is the detail of elements inside spring container:
The view resolver purpose is to resolve various types of views for example jsps, pdf multipart files(i.e. attachments) etc. Spring provide multiple view resolver implementations and we can use more than one view resolvers in a single spring container as well.
Below code use the springs Internalviewresolver and we also specify the location and suffix of our view classes.

Next is an entry for component scan which is required to read annotation based configuration inside java files:

Here we specified ** to specify search all files in the folder and its subfolders.

There is also an entry to load messages.properties file from the classpath but that’s not part of spring mvc.
Now we will create a spring controller and here is the code for the same:

package com.springaddon.mvc.controllers;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class BeerController {
private static Map beerMap = new HashMap();
static{
	beerMap.put("lite", "Corona, ");
	beerMap.put("strong", "Kingfisher");
	beerMap.put("extraStrong", "Haywards");
}
@RequestMapping(value="/selectBeer.htm", method=RequestMethod.GET)
public ModelAndView selectBeerType(HttpServletRequest request){
	return new ModelAndView("index");
}
@RequestMapping(value="/getBeer.htm", method=RequestMethod.GET)
public ModelAndView getBeer(HttpServletRequest request, @RequestParam String beerType, Model model){
	model.addAttribute("suggestBeer", beerMap.get(beerType));
	return new ModelAndView("getBeer");
}
}

All we need to define a controller is put an @Controller annotation above the class name.
Then above each method we will add an annotation for request mapping @RequestMapping
From selectBeerType we return a ModelAndView which is a combination of view name (found using view resolver configuration) and model attributes similar to request attributes.
The index.jsp is also our default view. This will present us a drop down of beer types.
When the user selects a beertype and click get beer button getBeer method will be invoked and it will return getBeer view with the name of the beer set as a model attribute.
Please note that the user selection is autobinded using @RequestParam.
Jsp code is very primitive and does not need much explaination.
Note1: This example can be extended to a complete form submission by setting some model attributes inside selectBeerType method and index.jsp showing the empty form and when user submits then the complete form data will be send inside a command object @ModelAttribute. The same will be processed (or persisted) and the result sent back to user.
Note2 : RequestMethod restrict the request to a particular http method else spring container maps the request with other http methods as well.

Please find the code attached below. Try it and let me know if you have any problems or questions.

spring-mvc-basic

Please feel free to leave your comments/feedback on this.

Thanks !

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