A Spring MVC web application, noticed all the Spring’s beans are loaded twice!?

package com.mkyong.config.db;
@Configuration
public class MongoDevConfig {
	private final static Logger logger = LoggerFactory.getLogger(MongoDevConfig.class);
	@Bean
	MongoDbFactory mongoDbFactory() throws Exception {
		logger.debug("Init...... MongoDbFactory() in production mode!");
		//...
		return new new SimpleMongoDbFactory(mongo, "db");;

During Application startup :

2015-03-05 17:52:32 DEBUG c.m.config.MongoLiveConfig - Init...... MongoDbFactory() in production mode!
2015-03-05 17:52:32 DEBUG c.m.config.MongoLiveConfig - Init...... MongoDbFactory() in production mode!

1. Spring Configuration

Here is the Spring MVC configuration.

<web-app>
	<servlet>
		<servlet-name>mvc-dispatcher</servlet-name>
		<servlet-class>
			org.springframework.web.servlet.DispatcherServlet
		</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>mvc-dispatcher</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
	<listener>
		<listener-class>
			org.springframework.web.context.ContextLoaderListener
		</listener-class>
	</listener>
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
	</context-param>
</web-app>

<beans...>
 	<context:component-scan base-package="com.mkyong" />
	<mvc:annotation-driven />
</beans>

2. Solution

Read this Spring DispatcherServlet reference to understand how Spring pick up the XML file :

Upon initialization of a DispatcherServlet, Spring MVC looks for a file named [servlet-name]-servlet.xml in the WEB-INF directory of your web application and …

In Above Spring configuration :

1. The servlet mvc-dispatcher will load mvc-dispatcher-servlet.xml
2. And the listener ContextLoaderListener will loadsmvc-dispatcher-servlet.xml again

To fix it, just renamed the servlet name mvc-dispatcher to something else.

<web-app>
	<!-- Now it will find hello-dispatcher-servlet.xml -->
	<servlet>
		<servlet-name>hello-dispatcher</servlet-name>
		<servlet-class>
			org.springframework.web.servlet.DispatcherServlet
		</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>hello-dispatcher</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>

In short, make sure Spring will not pick up the Spring XML configuration twice.

References

1. Spring IO : The DispatcherServlet
2. StackOverflow : spring web, security + web.xml + mvc dispatcher + Bean is created twice