Monolithic Struts application to modules cookbook ?

[Karma Struts <ka...@yahoo.com>]

Hi all,

We are currently trying to split an existing Struts
application into sub-modules, but it seems it is not
as easy as it is usually said in the short articles we
have found about it.

So, I'll try to explain a bit more where we are and
what we have done until now.

1. File structure
-----------------

We have a classical Struts web-app directory
structure, with a sub-module as follows:

*.jsp
/WEB-INF - web.xml
         - struts-config.xml
         - tiles-definitions.xml
         - validator.xml
         /lib
         /classes/ourPackage - *.java
/scripts
/stylesheets
/templates
/testsubmodule
         *.jsp
         /WEB-INF - struts-config.xml
         /classes/ourPackage - *.java

2. Web.xml
----------

In our web.xml file, we have added the following xml
for the new sub-module: 

<init-param>
   <param-name>config/testsubmodule</param-name>
  
<param-value>/testsubmodule/WEB-INF/struts-config.xml</param-value>
</init-param>

3. struts-config.xml
--------------------

Then we have added the necessary ActionMapping entries
for this sub-module. These definitions are loaded and
the mapping is working fine. We only have
ActionMapping AND FormBeans really used by this
module.  Anyway, sometimes determining which FormBeans
from your root application is also used by your
sub-module is not easy.  Duplicating everything can
maybe be an easy solution.
As far as we have read and from our experience, it
seems that RequestProcessor, MessageResources and
PlugIns have to be duplicated from the root
struts-config.xml file.  Is this correct ? 
We have also created a SwitchAction and a global
forward:

<forward name="gotoTestModule"
path="/toTestModule.do?page=/bodyTest.jsp&amp;prefix=/testsubmodule"
/>

and

<action path="/toTestModule"
type="org.apache.struts.actions.SwitchAction"/>

As the path attribute is context-relative, there can
be a mapping in the root that has the same name as one
in the sub-module, i.e.
http://myserver/myapp/myaction.do is different from
http://myserver/myapp/testsubmodule/myaction.do
 
4. JSP and Tiles
----------------

Of course, accessing the stylesheets, scripts and
templates from the JSP files in the sub-modules must
be context (path) relative too. So one solution is to
use a relative path to the files, i.e.
./stylesheets/mycss.css for JSP in the root directory,
and ../stylesheets/mycss.css for JSP contained in the
testsubmodule directory.
Another solution can be to use a <BASE> tag in order
to set the base URI to the application URI. As we are
using tiles, this tag can be added in the main tile
file. But in this case, it is important to take care
about links used in the JSP.  But can it lead to
unexpected problems ?

5. Java
-------

Access to Java objects doesn't seem to have problems
in the sub-module, wherever they are located (root or
sub-module), if the objects in the sub-module are well
compiled.

6. Problems
-----------

Seems that our main problems are due to incorrect
context. 
First of all, as we use tiles, and that the main tile
template is contained in the root, <html:form> and
calls to mapping.getName() inside the template JSP are
NOT in the sub-module context.  So the ActionMapping
defined in the sub-modules are not known.  Well, first
of all, we don't use the SwitchAction yet, but will it
solve our problem ? Also another solution may be to
duplicate the template tile in our sub-module, and use
it instead of the one in the root directory.  For the
moment, we have found in the mailing list archive what
I would call a temporary solution, using
org.apache.struts.util.RequestUtils.selectModule("testsubmodule",request,application)
before any form or call to the mapping Object.
Another problem is that we are using a tile with two
frames.  If the first one is an action from the root
directory, and the second frame is an application from
the sub-module, and that they are called from a JSP in
the sub-module, then we can use the SwitchAction to
call both parts.  But the problem is that the final
context will be the last one called, i.e. the one from
the second frame.  So if we do some action in the part
from the root directory, it doesn't work as it thinks
the context is now the one of the sub-module.
Well, in general, it seems not easy, and needs more
care, to be sure to be in the right context for any
action that can be made from one JSP, which can be a
headache if you are using multiple tile levels.  

So, if anyone can help us giving some good pieces of
advice regarding our current work, or to complete this
text, he/she is welcome.
If I've got new information, I'll add it to this
thread too.

Thanks a lot

Alexandre Dumortier
 

=====
KARMA Project - Development Team

__________________________________
Do you Yahoo!?
Yahoo! Finance: Get your refund fast by filing online.
http://taxes.yahoo.com/filing.html

---------------------------------------------------------------------
To unsubscribe, e-mail: struts-user-unsubscribe@jakarta.apache.org
For additional commands, e-mail: struts-user-help@jakarta.apache.org