A couple of weeks ago I asked this forum on how to implement scripted
Actions in order to speed up development. I received a couple of ideas which
I tried to implement. Unfortunately none of these ideas meet my
requirements. Below is a kind of a small analysis.
Requirement:
Instead of writing (compiling and deploying) Action classes, I'd like to use
scripts based on Jython, Groovy, etc..
Problems:
How to define the Action using xwork.xml? According to the DTD, attribut
"class" must be a class which implements at least the Action interface. It
can not be a script. The first solution that comes in mind is to define a
class may be com.eds.webwork.action.ScriptedAction and use param-tag to
reference the script to be executed.
<action name="editProdukt"
class="com.eds.webwork.action.ScriptedAction">
<param name="script" type="myScript.gy" />
...
</action>
What is the problem with that?
BSF (bean scripting framework) is "standard" for executing scripts and
supports multiple scripting languages. Unfortunately the BSF API supports
only calling a script. You can not define and read variable used by the
script. You can not call methods. It is like a command line and you start a
program.
I implemented a simple ScriptedAction class extending ActionSupport and
calling a script while executing the execute() method. That was easy. But it
does not work. Depending on the Interfaces your Action class needs to
support, you'll have to wirte more than one ScriptedAction class. One for
each combination of Interfaces. And think about the number of parameters you
have to forward to the script. Sounds like this is not the ideal solution.
Because of some issues with BSF (might be my limited knowledge of bsf,
xwork/webwork as well), I tried using Groovy. Besides the script API, Groovy
also supports a reflection like api which allows to create Objects, call
methods, access and define variables etc.. Using the Groovy reflection like
API was fairly straight forward. But I have still the same problem. I need
several ScriptedAction classes.
So far I have not found a feasable solution. What might be a solution (not
implemented yet).
The features Groovy provides (load a class, call methods, implement and
extend interfaces, etc.) are very much like, though not identical, to Java
and Javas reflection api. Which made me think about using different
"actionLoaders". Maybe something like
<action name="editProdukt"
actionloader="com.eds.webwork.classloader.ScriptClassLoader"
classname="myScript.gy" >
...
</action>
Default would be the java's "default" functionality and ScriptedClassLoader
might be used for Groovy classes. Depending on the loader used, the class
attribute will have a different meaning. Issues with this approach:
The script language must be very very similar to Java suppporting objects
and interfaces and must be able to extend native Java classes. From what
I've read, Groovy would be a candidate.
The script language meta api must support reflection like interfaces to
create object, call methods introspection etc.
Xwork must support multiple loaders which not only load the objects but
which invokes the differents reflection like APIs as well. Kind of a
factory. That sound like its not a small change.
Sounds to me that using scripted Action with WebWork is not as easy to
implement as I originally thought. May be I missed something. I'd happy to
discuss may experience in order to find a solution. Or am I the only one
believing that scripted action will make development easier and faster and
still have the option of using Java actions if performance or any other
constraints require it?
regards
Juergen
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