Spring MVC component Scan does not pick up controller

All,

I am trying to setup a new Spring MVC project and have created a dummy controller.
The problem that i am facing is Spring is not creating the bean of the controller. otherwise the logging statement inside the constructor should have printed.
The package of the controller is also defined in the beans configuration xml.

<context:component-scan base-package="com.blah.apps" annotation-config="true"/>

Spring Version: 5.2.8
Tomcat Version: 8

There is a specific reason why i am using the above versions and using xml based configuration.

The error that i get is:

Aug 25, 2020 10:53:02 AM org.springframework.web.servlet.DispatcherServlet noHandlerFound
WARNING: No mapping for GET /[app-name]/health

which is not surprising considering the bean did not get created.

Please find the code below...

package com.blah.apps.xyz.shopping.health;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class HealthController {

public HealthController() {
		System.out.println("Event this is not getting printed...the component scan should allow spring bean discovery..");
	}


	@ResponseBody
	@RequestMapping(value = "/health")
	public String getHealth() {
		return "App is running!";
	}
}

My Web.xml is

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://xmlns.jcp.org/xml/ns/javaee"
	xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
	id="WebApp_ID" version="3.1">
	<absolute-ordering />
	<servlet>
		<servlet-name>dispatcherServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>dispatcherServlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>

The dispatcherServlet-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:mvc="http://www.springframework.org/schema/mvc"
	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  
        http://www.springframework.org/schema/mvc  
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">

<mvc:annotation-driven />

<!-- have tried removing annotation-config as well-->

	<context:component-scan
		base-package="com.blah.apps" annotation-config="true"/> 
</beans>

You need to add a listener in your web.xml to load you Spring context.

<listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<context-param>
  <param-name>contextConfigLocation</param-name>
  <param-value>/WEB-INF/dispatcherServlet-servlet.xml</param-value>
</context-param>

<servlet>
  <servlet-name>spring</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <init-param>
    <param-name>contextConfigLocation</param-name>
    <param-value></param-value>
  </init-param>
</servlet>

Well since you are using Spring mvc, you should have a listener i.e. ContextLoaderListener in your web.xml. Add the below code in your web.xml.

 <listener>
      <listener-class>
        org.springframework.web.context.ContextLoaderListener
      </listener-class>
    </listener>
      
    <context-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>/WEB-INF/spring/applicationContext.xml</param-value>
    </context-param>

<servlet>
  <servlet-name>spring</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <init-param>
    <param-name>contextConfigLocation</param-name>
    <param-value></param-value>
  </init-param>
</servlet>

DispatcherServlet primary purpose is to handle incoming web requests matching the configured URL pattern. It take an incoming URI and find the right combination of controller and view.

ContextLoaderListener creates the root application context and will be shared with child contexts created by all DispatcherServlet contexts. Its job is to take the Spring configuration files as input and creates the Spring-managed beans as per configuration and make it ready during server startup and destroys them during server shutdown.

If you want to read more about ContectLoaderListener do visit https://www.java67.com/2019/05/contextloaderlistener-in-spring-mvc-10.html.

All,

Finally figured out what the problem was. The code was all correct... Even though the target folder had the controller class files, eclipse was changing the default output folder to project specific output folder (even though I have not specified anywhere.. not sure why this is hapenning on every build...).