Question

Starting my way with STS and created a new basic “Hello World” Spring MVC project.
I wanted to add a filter to my app so I created a filter (HelloWorldFilter.java) with the following doFilter method:

public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        System.out.println("Entering Filter");
        request.setAttribute("hello", "Hello World from HelloWorldFilter!");
        chain.doFilter(request, response);
        System.out.println("Exiting HelloWorldFilter");
    }

According to what I read it (my filter) should also be defined in the application context as a spring bean (Spring delegates it to my filter – from this manual )

So in my application context I have:

<bean id="helloWorldFilter" class="com.yl.mvc.filters.HelloWorldFilter"> </bean>

My web.xml contains the following:

<filter>
    <display-name>HelloWorldFilter</display-name>
    <filter-name>HelloWorldFilter</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
    <filter-name>HelloWorldFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

In my .jsp file I added:

<P><%=request.getAttribute("hello")%></P>

But all I see in my web-page is null (I expected Hello World from HelloWorldFilter!).
The filter doesn’t even get invoked..

Am I missing something here?

Thanks in advance,
Yogi

Answer 1

Ok go it solved.

The filter (which is a spring bean) must have the same name in the bean definition (in the application context) as that in the filter-name element (in the web.xml).

In my case I had in my application context:

<bean id="helloWorldFilter"...

and in my web.xml:

<filter-name>HelloWorldFilter</filter-name>

So once it is with a capital H and once a small h – which caused the issue.
To resolve it I simply changed the bean id in my application context to HelloWorldFilter.