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Question

Case 1

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

Case 2

  <servlet-mapping>
    <servlet-name>myapp</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>

If I use case 1 then I dont get any of my pages styled with <link rel="stylesheet" type="text/css" href="${contextPath}/assets/styles.css" />, but if I use case 2 everything gets styled.

Could someone help me understand why?

Also, could someone tell me which pattern should be used so that I don't have to worry about extensions? Like should I be using /*? The thing is that if I use /* now when I've been using *.do while developing my application, everything seems to be breaking, not only the styles but I don't get any pictures rendered, no JCaptcha and all that has to do with links.

And If I try to send a GET request from a REST Client like http://localhost:8080/myapp/user/1 it doesn't work and I need to add .do at the end and send the same request like http://localhost:8080/myapp/user/1.do.

Thanks.

score 4 · Accepted Answer · answered Jul 03 '11 at 16:43

Browsers sends separate HTTP requests on linked resources such as CSS files, JS files and images. The URLs of those requests also match the URL pattern of /. So your myapp servlet is also called on those requests. However, your myapp servlet doesn't seem to process them properly, so those requests returns something entirely different. Try requesting those resources yourself separately to learn what your servlet is actually returning to the webbrowser:

http://localhost:8080/myapp/assets/styles.css

In your case, you want to let your myapp servlet ignore requests on those resources. The best way is to create a filter which does that. Assuming that all of those resources are in a folder called /assets, then you can achieve this by mapping your servlet on a more specific URL pattern, such as for example /myapp/* and creating a Filter listening on /* which transparently continues the request/response chain for any requests on /assets and dispatches all other requests to /myapp.

So, this configuration

<filter>
    <filter-name>filter</filter-name>
    <filter-class>com.example.Filter</filter-class>
</filter>
<filter-mapping>
    <filter-name>filter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
    <servlet-name>controller</servlet-name>
    <servlet-class>com.example.Controller</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>controller</servlet-name>
    <url-pattern>/myapp/*</url-pattern>
</servlet-mapping>

in combination with the following in filter's doFilter():

String uri = ((HttpServletRequest) request).getRequestURI();
if (uri.startsWith("/assets")) {
    chain.doFilter(request, response); // Goes to container's default servlet.
} else {
    request.getRequestDispatcher("/myapp" + uri).forward(request, response);
}

should work for you.

`http://localhost:8080/myapp/assets/styles.css` is giving me the `styles.css` file If I change the `` from `*.do` to `/something/*` but if I change it to `/*` it gives me a `404` error. All the links seem to be working when I add a `/something` after the the context path. Will try to implement the same thing you answered above with Spring 3, as I have been using Spring 3 Controllers in the application. Just one more thing, could you help me understand why do I get a 404 error when I try `http://localhost:8080/myapp/assets/styles.css` for `/*` but not for `/something/*`? — skip, Jul 04 '11 at 11:27
Because the `/*` also matches that request on `styles.css`. However, the controller servlet apparently don't understand what to do with it, so it returns 404. — BalusC, Jul 04 '11 at 18:27

Stephen C · Answer 2 · 2011-07-03T11:59:31.047

Here is the relevant page from the Oracle J2EE Tutorial: http://download.oracle.com/docs/cd/E13222_01/wls/docs81/webapp/components.html#148787

This page gives some examples, and refers the reader to the Servlet specs:

For more information on servlet mappings, such as general servlet mapping rules and conventions, refer to Section 11 of the Servlet 2.3 specification at: http://www.jcp.org/aboutJava/communityprocess/final/jsr053/

The spec is worth a read, but you need to click an "I agree" to download the PDF, so I can't link to it directly.

A summary of what the spec says is that the following rules are used (in order):

An attempt is made to perform an exact match.
An attempt is made to do a prefix match, with priority given to the match with the longest prefix.
An attempt is made to do a suffix match.
"[T]he the container will attempt to serve content appropriate for the resource requested. If a "default" servlet is defined for the application, it will be used."

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