[MVC]Why in this example I have to use annotation-driven tag? Difference beetwen component-scan

[Andrea Nobili]

Some days ago I begin to study this Spring Hello World Tutorial: http://viralpatel.net/blogs/spring-3-mvc-create-hello-world-application-spring-3-mvc/

In this tutorial Spring DispatcherServlet is configured using the spring-servlet.xml file, this one:

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <context:component-scan base-package="net.viralpatel.spring3.controller" /> <bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" /> <property name="prefix" value="/WEB-INF/jsp/" /> <property name="suffix" value=".jsp" /> </bean>

In this file I am using the context:component-scan tag to say that Spring have to scan my file serching the annotation, so for exemple, when in the controller class find that a method is annoted by @RequestMapping("/hello") annotation know that this method handle the HTTP Request toward the URL ending with "/hello". This is simple...

Now my doubt is related to the Spring MVC template project that I could automatically build in STS\Eclipse

When I create a new Spring MVC project in STS I have that my DispatcherServlet is configured by a file named servlet-context.xml that contains some configuration similar to the previus example file.

In this file, I still have the component scan tag:

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

but I have also another tag (that look like have similar task), this one:

<annotation-driven />

What is the difference between these two tags? between these two tags?

An other "strange" thing is that the previus example (that don't use the annotation-driven tag) is very very similar to the project create by STS using the Spring MVC Template project but if I delete the annotation-driven tag from its configuration file the project don't run and give me the following error: HTTP Status 404 -

And in the stacktrace I have:

WARN : org.springframework.web.servlet.PageNotFound - No mapping found for HTTP request with URI [/maventestwebapp/] in DispatcherServlet with name 'appServlet'

But why? In the previus example work well without annotation-driven tag, and this controller class is very similar...infact have only one method that handles HTTP request toward "/" path

This is the code of my controller class:

package com.mycompany.maventestwebapp;

import java.text.DateFormat;
import java.util.Date;
import java.util.Locale;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * Handles requests for the application home page.
*/
@Controller
public class HomeController {

private static final Logger logger = LoggerFactory.getLogger(HomeController.class);

/**
 * Simply selects the home view to render by returning its name.
 */
@RequestMapping(value = "/", method = RequestMethod.GET)
public String home(Locale locale, Model model) {
    logger.info("Welcome home! The client locale is {}.", locale);

    Date date = new Date();
    DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, locale);

    String formattedDate = dateFormat.format(date);

    model.addAttribute("serverTime", formattedDate );

    return "home";
}

Can someone help me to understand this thing?

Thank you very much

Andrea

[Bill Gorder]

Please have a look at this thread.
http://www.coderanch.com/t/586286/Spring/mvc-annotation-driven-context-annotation