At 07:18 AM 6/18/2004, Bill Schneider wrote:
Form beans can be thought of as a special case of DTOs: they are the argument the client (web browser) passes to the remote method call (HTTP POST). So passing form beans directly to business logic is _almost_ reasonable, putting the dependency issue aside for now (form beans have to extend ActionForm).
The difference is, form beans are a model of the /user input/, and since there may be invalid inputs (for example: "asdfjkjkd" in a field that's supposed to be numeric) form bean fields often need to be Strings when the corresponding field in a "real" DTO would be a Date or Integer.
To deal with this, I've used a tool called XSnapshot (just released to SourceForge: http://xsnapshot.sourceforge.net) to generate form beans and other DTOs from XDoclet tags in a POJO data model. That way you get _both_ real DTOs and Form Beans without writing all the classes by hand, and you can copy between DTOs and form beans with BeanUtils.copyProperties.
-- Bill -- Bill Schneider Chief Architect
I don't think we should be thinking of action forms as DTOs. DTOs or VOs have a special use and a special problem that they are meant to solve. Action forms are related to an entirely different set of issues about data farming. I don't think we can put the dependency issue aside. That is really the whole point of frameworks like Struts. If you can put the dependency issues aside, you probably don't need Struts. If you don't need a hammer, that is not a critique of a hammer. Likewise, Struts has an objective and, with clear areas that could be improved, does that really well. There is a good reason that Struts is so successful. Craig is a sweetheart, but that is not the reason for the success of Struts.
I think that a lot of the problems people have with repetitive programming is not the fault of the framework but the failure to use coding techniques that are readily available, such as dynamic proxies.
Michael
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