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Tags/Keywords : Spring web, Spring mvc, Spring example, Example, Code, Tutorial, Article
Author : Amit
Date (Year/Month/Date): 2010-06-24
Working on some example using Spring WEB module

Please be informed that NONE of the design/code/matter from this page is claiming to be some
sort of best practice and we DO NOT expect any of our visitor/reader of this page to assume
this as some sort of best practice for any context and should not be using this as it is
without appropriate evaluation.
This page intends only to provide bits and pieces of known ways  for doing some sort of example
and may not be fit for any other purpose.

In spite of all precautions taken to provide accurate and avoid any typo in these pages,
there might be some issues like grammatical mistakes and typo being observed in these pages,
We extend our sincerest apologies for the same.


In this Page I am going to show and describe an example
using SpringFramework's Web and MVC related functionality.

To start with I am not going to write any custom class or POJOs
and not use any annotations, but I am going to use Spring's
own implementations for URL handling/mapping and Controller.

I assume that you as a reader have already know besics about
Spring core, web modules and know how to use these.

In this example/page I am not going to explain / provide 
definitions for all these components/modules.

Here I am going to use some of the modules/JARs from 
SpringFramework as follows:

org.springframework.aop-3.0.0.RELEASE.jar
org.springframework.asm-3.0.0.RELEASE.jar
org.springframework.aspects-3.0.0.RELEASE.jar
org.springframework.beans-3.0.0.RELEASE.jar
org.springframework.context-3.0.0.RELEASE.jar
org.springframework.context.support-3.0.0.RELEASE.jar
org.springframework.core-3.0.0.RELEASE.jar
org.springframework.expression-3.0.0.RELEASE.jar
org.springframework.web-3.0.0.RELEASE.jar
org.springframework.web.servlet-3.0.0.RELEASE.jar

These JAR files along with some other files placed in the 
WEB-INF/lib folder, as follows:

commons-logging-1.1.1.jar
log4j-1.2.15.jar

There are two main configuration/descriptor files such as
"web.xml" and "example-web-controller-servlet.xml"

The section in bold red in the file name is same as that
of the entry in web.xml file as follows:

/WEB-INF/web.xml


<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
   version="2.5"> 
  <servlet>
    <servlet-name>example-web-controller</servlet-name>
	<servlet-class>
	  org.springframework.web.servlet.DispatcherServlet
	</servlet-class>
	<load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>example-web-controller</servlet-name>
	<url-pattern>*.go</url-pattern>
  </servlet-mapping>
</web-app>


As you might have noticed that the web.xml file is having
declaration for the web app as web-app_2_5.xsd, so I have tested
this example on Tomcat web server version 6.0.18.

So the web.xml descriptor file is having a Spring's DispatcherServlet
configured to be load on web server startup.

Spring Framework requires a *-servlet.xml file for automatically
using this file for context related operations. So this file
example-web-controller-servlet.xml is having some tags used
such as follows:



<?xml version="1.0" encoding="UTF-8"?>
<beans 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-2.0.xsd">
   <bean id="exampleController" 
    class="org.springframework.web.servlet.mvc.UrlFilenameViewController">  
     <property name="prefix" value="/"/>
     <property name="suffix" value=".jsp"/>
   </bean>
  <bean id="exampleHandlerMapping" 
   class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="urlMap">
      <map>
        <entry key="test.go" value="exampleController"/>
      </map>
    </property>
  </bean>
</beans>


As mentioned above, I am going to use 
org.springframework.web.servlet.handler.SimpleUrlHandlerMapping as 
handler mapping implementation and 
org.springframework.web.servlet.mvc.UrlFilenameViewController as
controller.

The URL that I used to test this application is :

http://localhost:8080/example-spring-web/test.go

After completing the above example, I moved on to a slightly
different approach, whereby I created a custom/user defined
controller by implementing Spring's Controller interface          
and providing implementation for the abstract handleRequest
method, as shown below:

ExampleController.java


package example.controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

public class ExampleController implements Controller{
	public ModelAndView handleRequest(HttpServletRequest request,
			                          HttpServletResponse response) 
	                                  throws Exception {
     return new ModelAndView("/test.jsp");
	}
}


It does nothing apart from just returning the ModelAndView
instance along with the destination JSP file.

Now there is a little bit of change in the *-servlet.xml file as well:

example-web-controller-servlet.xml



<?xml version="1.0" encoding="UTF-8"?>
<beans 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-2.0.xsd">
   <bean id="exampleController" 
    class="example.controller.ExampleController">  
   </bean>
  <bean id="exampleHandlerMapping" 
   class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="urlMap">
      <map>
        <entry key="test.go" value="exampleController"/>
      </map>
    </property>
  </bean>
</beans>


These changes works pretty the same way it is expected to.
On exploring the following  URL, it is observed to show the output
from the test.jsp file as expected.

http://localhost:8080/example-spring-web/test.go

Then I moved onto another  phase of this example by exploring
some other ways of making this example work. I managed to do
this by changing/using some other type of handler mapping from
SpringFramework WEB module.

I used 
org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping

As per the official documentation from Spring, this handler mapping
automatically picks up bean that is defined with a name matching with
that of the URI, for this example, the bean that is required to be defined
with a name as "/test.go" and the class I used as that of the 
ExampleController, as shown in the following section:

example-web-controller-servlet.xml


<?xml version="1.0" encoding="UTF-8"?>
<beans 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-2.0.xsd">
  <bean id="exampleHandlerMapping" 
   class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping">
  </bean>
  <bean name="/test.go" class="example.controller.ExampleController"/>
</beans>


http://localhost:8080/example-spring-mvc/test.go
So the URL has the URI as /test.go, and it is mapped to the ExampleController.
Thus ExampleController returns the view as "/test.jsp".

Hope this helps.

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