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From "Craig R. McClanahan" <>
Subject Re: Images and STRUTS
Date Wed, 03 Apr 2002 18:12:36 GMT

On Tue, 2 Apr 2002, Micael Padraig Og mac Grene wrote:

> Date: Tue, 02 Apr 2002 22:29:28 -0800
> From: Micael Padraig Og mac Grene <>
> Reply-To: Tomcat Users List <>
> To:
> Subject: Images and STRUTS
> I tried to do an ordinary image tag with the struts application, and could
> not.  What is happening with that?  I could not get the index.jsp page to
> reference an image in the same location.  I used the same page without
> struts, and it worked.  I am just getting the clue on struts.  I am
> familiar with the whole of Model 2 architectures, just not struts.  Is it
> the forwarding mechanism that is calling the problem?

You probably want to ask this sort of question on the STRUTS-USER list
instead of here, but here's a common scenario that can cause Struts users
(or anyone else using an architecture that uses RequestDispatcher.forward)
grief:  if you are using relative path references for your images, those
paths get resolved against the request URI that the browser submitted to
-- not the URI of the page itself.  This is because the browser has no
clue that a RequestDispatcher.forward() call was done on the server side.


- Your app is installed at "http://localhost:8080/myapp"

- You have a main page "index.jsp", which therefore has the absolute URI

- You have an image in an "images" subdirectory, which therefore has the
  absolute URI "http://localhost:8080/myapp/images/logo.gif".

- You have Struts set up to use path based mapping to the controller
  servlet, so you get URIs like "http://localhost:8080/myapp/do/getCustomer"
  in it (to execute the "getCustomer" action).

Now, consider what happens if you have the following tag in index.jsp:

  <img src="images/logo.gif">

and you execute "http://localhost:8080/myapp/do/mainMenu".  This fails to
retrieve the image.  Why?  Because the *browser* is the one that resolves
the absolute URI of the image -- and it resolves it against the URI that
it submitted for this request:


which is obviously wrong.  Ways to get around this:

- (Struts-specific) Use extension mapping instead of path mapping
  for the controller.  Then, all requests and pages are in the same
  "directory level" and relative references work as expected.

- (Struts-specific) Use the <html:base/> tag in the <head> section
  of your index.jsp page.  This creates an HTML <base> tag that tells
  the browser to base relative references on *this* page, instead of
  the request URI of the submit.

- (Struts-specific) Use the Struts <html:img> tag instead, which knows
  all about this problem and generates the correct URI automatically.

- (General) Use a relative path like "../images/logo.gif" to convince
  the browser to do the path correctly.

- (General) Include your own <base> tag to tell the browser what the
  absolute URL of this page is.

> Micael


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