RE: [equinox-dev] JSP support in the servlet bridge incubator project

[Richard Backhouse <backhous@xxxxxxxxxx>]

Simon,

I should be able to contribute what
I have. How is it best to package it up for you ? 

Richard

"Kaegi, Simon" <Simon.Kaegi@xxxxxxxxxx>
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06/02/2006 01:27 AM

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Subject	RE: [equinox-dev] JSP support in the servlet bridge incubator project

Hi Richard,
 
Great post.
I found myself in agreement with
most of your observations and your approach definitely sounds interesting.

For my part I've been experimenting
with packaging so in particular I'm very curious to see the details of
how you've handled tag libraries. 
 
I think your work here sounds
excellent and is very much in line with what's going on. There's been considerable
interest in this problem so if you're willing to contribute your work here
that would be appreciated and really help things get moving. The RSP-UI
folk also alluded to similar work in their proposal so we might also have
that as source for a final solution.
 
There's an enhancement request
here (https://bugs.eclipse.org/bugs/show_bug.cgi?id=140430)
to track this work. I can update it with a bit more information, as we
now have the go ahead for using Jasper2, Commons EL, and Commons Logging.
Before we can really get going in the incubator we still need approval
for Servlet 2.4 and JSP 2.0 (hopefully not to long now). In the interim
I can certainly post what I've got in terms of packaging so we can perhaps
begin a discussion on how we might want to bundle this stuff. 
-Simon

---

From: equinox-dev-bounces@xxxxxxxxxxx
[mailto:equinox-dev-bounces@xxxxxxxxxxx] On Behalf Of Richard Backhouse
Sent: Thursday, June 01, 2006 1:48 PM
To: equinox-dev@xxxxxxxxxxx
Subject: [equinox-dev] JSP support in the servlet bridge incubator
project


I have spent a little time investigating supporting JSPs within the server
side OSGi incubator project. Having taken a look at what Harald Niesche
had achieved with his JasperBundle I felt that instead of having to prefix
all my JSP requests with "/jasper-jsp" it would be preferable
to support JSP's just as requests for static resources are handled.

Here is what I have put together : 

1.) Created a org.apache.jasper bundle containing the required Jasper jars
to run the JSP Container (commons-el.jar, jasper-compiler.jar, jasper-compiler-jdt.jar
and jasper-runtime.jar). This bundle is also a fragment bundle whose bundle
host is org.eclipse.equinox.servlet.bridge.http bundle. This allows references
to the Jasper classes to be made without having to add explicit imports
to the org.eclipse.equinox.servlet.bridge.http manifest.

2.) In the org.eclipse.equinox.servlet.bridge.http bundle I created a JspEnabledProxyServlet
class that extends the ProxyServlet class. Within this new class a single
JSPServletRegistration object is created that wrappers the Jasper org.apache.jasper.servlet.JspServlet.
Also a specialized JspServletHtpContext class has been created to handle
setting the correct resouce http context for the bundle that contains the
JSP resource. 

3.) In the org.eclipse.equinox.servlet.bridge.http bundle I created a JspEnabledResourceRegistration
class that extends the existing ResourceRegistration class and overides
the handleRequest method. When created it is passed a reference to the
JSPServletRegistration object .When the  handleRequest method is called
if the supplied alias has an extension identified as a JSP extension the
JSPServletRegistration object is used to handle the request instead of
the standard ResourceRegistration. 

4) All of the above is enabled by making some slight modifications to some
of the org.eclipse.equinox.servlet.bridge.http classes, specifically the
Activator class and the ProxyServlet class. The ProxyServlet changes were
simply changing some of the class attributes and methods to protected access.
The change to the Activator class was to invoke the new JspEnabledProxyServlet
instead of the standard ProxyServlet. The manifest for the org.eclipse.equinox.servlet.bridge.extensionbundle
was also modified to filter the javax.servlet.jsp classes down from the
running webcontainer. 
  
So this works nicely for any JSP resources configure via the standard resources
extension point but what if the JSP's reference Custom Tag Libraries ?
The solution I have come up with allows Custom Tag Libraries to be created
as standard OSGi bundles. They register their provided TLD's via a TldProvider
service I added to the org.eclipse.equinox.http.registry bundle. The JspEnabledProxyServlet
class tracks the registered services and adds their  TLD uri's to
the Jasper JSP Servlet. via an extended URLClassloader  I could have
achieved the registration of the TLDProviders by using a new extension
point added to the org.eclipse.equinox.http.registry bundle but getting
access to the registry details seemed as though it would be quite hard
to achieve in simple manor. 

Thoughts ? 

Richard Backhouse
 
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