Raible Designs

Integrating WebWork into AppFuse

Last week was a busy one as I was trying to finish up AppFuse 1.6 before starting my new gig (more on that later). Most of this involved 1) integrating WebWork and 2) writing the Ant-based installer for replacing Struts with WebWork. I've worked with WebWork before, so this post is mostly an extension of that - as well as documentation on what I did so others can understand AppFuse+WebWork better. Below is a list of things I found.

• WebWork's concept of "results" are very similar to Struts "action-forwards". However, they also allow you to chain to other actions and use expressions.
• Implementing the ModelDriven interface in your Actions is a good idea, but it's not that great. I found that by simply using get/setUser(), I got the same functionality - except that I had to add "user." to all my form elements in my JSP. The advantage to doing things this way (over ModelDriven) is you can have an Action that services many objects. The main reason I'm not using ModelDriven is because the following tag doesn't render the label (it's just blank). Strangely enough, it renders just fine after validation fails.

    <ww:textfield label="getText('user.firstName')" name="'user.firstName'"
        value="user.firstName" required="true"/>

• WebWork is similar to Tapestry in that they encourage you to specify i18n messages (properties files) on a per-action basis (Tapestry is per page). Some might think this is a good idea, but after using Struts and Spring, I'm used to using one ResourceBundle for everything. To migrate AppFuse from using 1 bundle to many bundles just for WebWork would've been a pain. Luckily, in WebWork 2.1, they added the ability to specify a custom bundle using "webwork.custom.i18n.resources=ApplicationResources" in webwork.properties. I believe my issue with ModelDriven and labels is caused by this new feature.
• The Spring-integration provided by SpringObjectFactory is quite nice. Unfortunately, client-side visitor validation doesn't work with it.
• Unit-testing WebWork actions is easy, though it's kinda wierd to not send request parameters and such to set values (instead, you just set values directly on the Action).
• I experimented with putting stuff on the stack and pulling it off in JSPs, but never got it to work quite right. After failing the 10 minute test, I decided to just put stuff in the request and get it working. Looking through the code now, there's only 3 places where I'm stuffing attributes into the request: 2 in FileUploadAction and 1 in ExceptionHandlerInterceptor.
• With most frameworks I've used in the past, I rarely jumped into the source to try and see how things worked. Because of this, I rarely extended framework classes for my own use. However, with WebWork/XWork, I found it quite easy to dig in and extend the framework. Especially with Interceptors - which I dig.
• Following up on Interceptors, I was able to easily create my own ValidationInterceptor that cancels validation on GET requests, and when cancel or delete is clicked.
• Other interceptors that came in handy are a UserRoleAuthorizationInterceptor (which I borrowed from Spring) and an ExceptionHandlerInterceptor (which is modeled after Spring's SimpleMappingExceptionResolver). The 1st interceptor made it easy to mimic Struts' ability to declare a "roles" attribute on an action-mapping. The 2nd one allows you to map exceptions to results. This is something I was looking for when I first started using WebWork.
• The "required" attribute in WebWork's JSP tags have nothing to do with validation, except that they add an asterisk to the field label. I'd rather this be integrated with validation - where an asterisk shows up when a field is "required" in its Action/POJO-validation.xml file.
• I had a few other issues with validation: client-side validation shows one error at a time, client-side validation doesn't allow cancelling and field errors are displayed in a random order. If I were to start a project tomorrow that wanted WebWork with client-side validation, I'd probably try to integrate Commons Validator.
• Testing Actions is easy, as it should be. Using Spring's Servlet API mocks made it easy to test Actions that used ServletActionContext to set cookies and other such request-related stuff.
• I dig the rich set of form tags and it's great that these can be easily customized. I customized a few for AppFuse to make the syntax a bit more XHTML-compliant.
• I'm a stickler for formatting and good-looking XHTML in JSPs. I try to keep lines less than 80 characters. Here's a comparison of the LOC required by the different frameworks for userForm.jsp:
  • Struts: 298
  • Spring: 319
  • WebWork: 186

All in all, I enjoyed working with WebWork and if given a choice of an AppFuse combination to use on my next project - it would probably be WebWork+Hibernate. If the client wanted client-side validation, I'd either integrate Commons Validator (which shouldn't be too hard) or use Spring+Hibernate. After using Spring and WebWork, which allow you to use your model objects directly in the view, it would be tough to go back to Struts. However, I still do know Struts better than the other two - so if I had a really tight deadline, that might be the smart way to go.