Servlet sample "navimage.png.java" from CQ5-Docu "How to get fully featured Website" does not work.

Question

When working on the sample described in "How to create a fully featured Website", I got an error in the part "Creating the Top Navigation Component". I have discussed this at the page itself (see the comments there) and in the sling mailing list. I was told,  this forum would be the best place to find a solution. So I will ask the remaining question here:
The sample uses a servlet "navimage.png.java" to create dynamically top navigation buttons with a meaningful text displayed.
We have got a node "/content/mywebsite/en/products" (there are more, but it is easier to explain when focusing on one of them) with jcr:primaryType=cq:Page with childnode jcr:content with the property sling:resourceType=mywebsite/components/contentpage.
The path "/apps/mywebsite/components/contentpage" contains a node body.jsp. The request http://localhost:4502//content/mywebsite/en/products.html renders the node /apps/mywebsite/components/contentpage/body.jsp.
The body.jsp includes another jsp "topnav.jsp" which refers to /content/mywebsite/en/products.navimage.png by the expression "src="<%= child.getPath() %>.navimage.png"></a><%".
The servlet "navimage.png.java" has been placed to /apps/mywebsite/components/contentpage/navimage.png.java. See inserted screenshot for the layout.
When issuing the request, none of the expected buttons is displayed. The "Recent Requests"-tab at the OSGi-Console shows a whole bunch of message requests.
The "GET customers.navimage.png", "GET services.navimage.png" and "GET products.navimage.png" tell me, that the request has been resolved (excerpt from the messages):
  10 (2013-02-01 15:45:18) LOG Including resource JcrNodeResource, type=mywebsite/components/contentpage, superType=null, path=/content/mywebsite/en/products/jcr:content (SlingRequestPathInfo: path='/content/mywebsite/en/products/jcr:content',  selectorString='navimage', extension='png', suffix='null')
     10 (2013-02-01 15:45:18) TIMER_START{resolveServlet(JcrNodeResource, type=mywebsite/components/contentpage, superType=null, path=/content/mywebsite/en/products/jcr:content)}
     10 (2013-02-01 15:45:18) TIMER_END{0,resolveServlet(JcrNodeResource, type=mywebsite/components/contentpage, superType=null, path=/content/mywebsite/en/products/jcr:content)} Using servlet /apps/mywebsite/components/contentpage/navimage.png.java
     10 (2013-02-01 15:45:18) LOG Applying Includefilters
But the "GET navimage.png" does not find anything:
  10 (2013-02-01 16:08:06) TIMER_END{10,ResourceResolution} URI=/apps/mywebsite/components/contentpage/navimage.png resolves to Resource=NonExistingResource, path=/apps/mywebsite/components/contentpage/navimage.png
     10 (2013-02-01 16:08:06) LOG Resource Path Info: SlingRequestPathInfo: path='/apps/mywebsite/components/contentpage/navimage.png', selectorString='null', extension='png', suffix='null'
     10 (2013-02-01 16:08:06) TIMER_START{ServletResolution}
     10 (2013-02-01 16:08:06) TIMER_START{resolveServlet(NonExistingResource, path=/apps/mywebsite/components/contentpage/navimage.png)}
     10 (2013-02-01 16:08:06) LOG {0}: no servlet found
So the servlet has been detected. Why isn't it displayed. When I place a real picture in the path (navimage.png) the sample works fine.
- What can I do to detect the cause of the error
- When becomes the servlet compiled and where is the class-file stored?
Thank you for your support.
Ulrich

Answer 1

I almost found it now. The reason was, that I had not copied (puposely!) the images-folder to the design-folder (/etc/design/mywebsite). The servlet itself requires a node from this folder
line 64: "String imgPath = new String(dg.getDesignPath(currentPage)+"/images/navimage_bg.jpg");"
line 65: "Layer bg = ImageHelper.createLayer(ctx.resolver.resolve(imgPath));"
The servlet must have failed and this is why I didn't see any buttons o my page.
I say, I have not supplied the images purposely, because I don't like to introduce too much stuff without knowing what it is meant for. I prefer to cause an error. Learning by researching errors is most of the time more effective than having something run without exactly to understand the prerequisites.
At the end this is also true for this case. I had many discussions on several platforms, read a lot of documents to go this short step.
Thank you.
Ulrich