Spring MVC - static resource handling with / servlet-mapping

A servlet mapping of "/" registers a "default" servlet - if a request comes in which matches a mapping in the web.xml file then the request will be handled by that servlet, however if no servlet is found matching a specific request pattern then the request is handled by the "default" servelt.

The "default" servlet is also responsible for handling the requests to the static content in a web application.

A convention for Spring MVC based applications is to register the Spring MVC Front Controller called the DispatcherServlet with a servlet mapping of '/'

    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:/META-INF/spring/web/webmvc-config.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>


    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

This enables Spring MVC to handle all the requests coming to the web application, except for cases where other specific mappings are available. A good example of a case where a specific mapping may be required is to configure the front controller for Apache CXF to accept webservice requests to /webservices servlet path:

 <servlet>
  <servlet-name>CXFServlet</servlet-name>
  <servlet-class>org.apache.cxf.transport.servlet.CXFServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>
 
 
 <servlet-mapping>
  <servlet-name>CXFServlet</servlet-name>
  <url-pattern>/webservices/*</url-pattern>
 </servlet-mapping>

Given that it is the "default" servlet which handles the request for the static resources like images, and the default servlet with Spring MVC is the DispatcherServlet, there are a few recommendations to serve out static content from Spring MVC based web applications:

1. Using mvc:resources -
For eg.

<mvc:resources mapping="/resources/**" location="/public-resources/"/>

This enables serving any static content whose location can be specified as a Spring Resource

2. Using mvc:default-servlet-handler:

 <mvc:default-servlet-handler />

This provides a way to serve out the static content from the root of the web application even though the Dispatcher Servlet is registered at /, the details of how Spring does this is available at the Spring documentation site here - in brief the responsibility is delegated to the containers default servlet.