Wednesday, April 21, 2004

The request, the session and the form

Struts sucks. Just kidding. Actually, struts really sucks. But it's better than nothing, and it's available everywhere, so like Microsoft Windows, it's the default bolt-on for J2EE webapps in spite of its short comings. And unlike Windows, it is open and free.

Complaints aside, I've been trying out three ways of passing data from an action to the corresponding controller:

Use the request
This is very sensible, but was not the initial approach in my current project. In the action stash the data as an attribute on the request, and fetch it back out in the controller. To ensure type safety, use wrapper methods and manifest constants (e.g., setFooId(Long) to set the FOO_ID attribute).
Use the session
This is similar to using the request, and was the initial approach in my current project, but leaves garbage littered about and occassionally tricks code into using an old value from a previous request. Avoid. I'm working on moving session-based code to request-based code as I encounter it.
Use the form
This is the most interesting choice. On the surface, the controller has no form to use, only the action has one. But the form is stored as an attribute in the request, and you can fetch it back out if only you know the key for it. Struts uses the name field of the form bean from struts-config.xml as the attribute name. This is nice if you know the name, but fragile if you ever change it. Better would be to take your action mapping, and use that to get at the form bean name. If this works, this would be the best choice of all.

Ah, but just how does one get at the action mapping from inside a controller? That is the question I am presently working on. One way is to use the request processor to give you the action mapping, but I don't know how to get the request processor. More research awaits.

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