Spring MVC RequestMapping

Question

I'm in the early stages of learning to use Spring MVC. I've created a controller and applied a RequestMapping annotation to it. When I run the project, the index page displays as expected at index.htm, but when I navigate to the URI that should be pointing to my controller, I get a 404 error, even though the controller seems to have been detected by Spring and started. Please help me understand what I am failing to grasp here:

Here is my web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 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_3_0.xsd">
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>
<session-config>
    <session-timeout>
        30
    </session-timeout>
</session-config>
<welcome-file-list>
    <welcome-file>redirect.jsp</welcome-file>
</welcome-file-list>

Here is my applicationContext.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"
   xmlns:context="http://www.springframework.org/schema/context" 

   xmlns:p="http://www.springframework.org/schema/p"
   xmlns:aop="http://www.springframework.org/schema/aop"
   xmlns:tx="http://www.springframework.org/schema/tx"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
   http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd  
   http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd
   http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd>

    <context:spring-configured/>

<context:component-scan base-package="org.blah.blah"/>

Here is my dispatcher-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"
   xmlns:context="http://www.springframework.org/schema/context" 
   xmlns:p="http://www.springframework.org/schema/p"
   xmlns:aop="http://www.springframework.org/schema/aop"
   xmlns:tx="http://www.springframework.org/schema/tx"
   xmlns:mvc="http://www.springframework.org/schema/mvc"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd  
                       http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd        
                       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd
                       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd">

<mvc:annotation-driven/>
<bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>

<bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="mappings">
        <props>
            <prop key="index.htm">indexController</prop>
        </props>
    </property>
</bean>

<bean id="viewResolver"
      class="org.springframework.web.servlet.view.InternalResourceViewResolver"
      p:prefix="/WEB-INF/jsp/"
      p:suffix=".jsp" />

<bean name="indexController"
      class="org.springframework.web.servlet.mvc.ParameterizableViewController"
      p:viewName="index" />

And, finally, here is my controller.

@Controller
@RequestMapping(value = "/hello")
public class Ctrl {

    @RequestMapping(method = RequestMethod.GET)
    @ResponseBody
    public String hello(){
    return "hello!";
    }

}

EDIT: This is what my browser displays:

Answer 1

I was half-wrong in the comments to gravityplanx' answer.

When you specify a <mvc:annotation-driven /> in your servlet configuration, Spring registers a RequestMappingHandlerMapping bean which is meant to collect and map all your @Controller handler methods, ie. those annotated with @RequestMapping.

It does this by looking at all the beans in the current context. Remember that when you load a context with DispatcherServlet, call it the servlet context, if a context was loaded by a ContextLoaderListener, call it the root context, the root context is made a parent of the servlet context. By default, the RequestMappingHandlerMapping bean does not look at the root context, which is a parent of the servlet context.

In your case, the @Controller beans are declared implicitly in the root context (your applicationContext.xml) because of the <context:component-scan/> which scans classes annotated with @Component or any of its specializations (@Controller for instance) and creates beans for them. So these beans are registered in the root context, where the RequestMappingHandlerMapping can't find them.

If instead you declare the <context:component-scan /> in the servlet context, then the @Controller (and other) beans are created in the servlet context where they are available to the RequestMappingHandlerMapping which can then register them to handle requests.

Note that <context:component-scan /> on its own doesn't do anything for the MVC stack. It needs further configuration, like <mvc:annotation-driven />. You should aim to specify packages that contain servlet specific beans in the servlet context and application wide beans in the root context.

Here's some literature:

• What is the difference between ApplicationContext and WebApplicationContext in Spring MVC?
• Difference between applicationContext.xml and spring-servlet.xml in Spring Framework

Answer 2

Your dispatcher servlet doesn't seem to be referenced correctly.

Replace:

<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>2</load-on-startup>
</servlet>

With:

<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>[insert the path to your dispatcher-servlet here]</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

And then move:

<context:spring-configured/>

<context:component-scan base-package="org.blah.blah"/>

From applicationContext to dispatcher-servlet