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The Sample Implementation
Even if you are familar with Jakarta Struts, it may be helpful to review the usual sequence of interactions in the Web application when using this framework. Figure 1 is a simplified UML sequence diagram showing how everything will work.
Figure 1: The Sample UML Segence Diagram
This is the typical path for all calls. While users are browsing your pages, they are forced to go to the Struts Controller, which selects the appropriate Action class. In turn, the Action class performs all the necessary calculations, operations, etc. and the result data is placed into a JavaBean. This bean is placed into a request (session, application) scope and a JSP page. The JSP page uses the data (from the JavaBean inside the request scope) to create a presentation view.
What about this "typical" process will you need to change? Without a doubt, you'll want to get rid of the JSP pages. With each Action code, you can create XML document with the result data, apply the XSLT stylesheet to it, and output everything. However, this working solution is a bit crude. Here's a much more elegant scheme. Follow the typical process. The result Java Bean gets created and put into the request scope. But now, return the control to the special XML/XSLT controller. Now, the sequence diagram looks like Figure 2.
Figure 2: The Improved Sample UML Segence Diagram
The XML/XSLT controller, with the help of the java.beans.Introspector, learns about properties and methods supported by the result JavaBean from the request scope. The controller uses this information, along with the DOM (Document Object Model) API, to create an XML document.
The following code is an example of the JavaBean class filled with result data:
public class SomeResultBean {
private String textField1;
private String textField2;
...
// getters and setters below
...
}
This results in the following XML file:
<?xml version="1.0" ?>
<root>
<SomeResultBean>
<textField1> some value </textField1>
<textField2> other value </textField2>
...
</SomeResultBean>
</root>
After the XML document is ready, the XML/XSLT controller receives the name of the XSL file from request scope (in your own Web application, you may decide to hard-code the name of the stylesheet, or put it into the result bean, or whatever else you want). Using the Transformations API for XML from the Xalan library, the controller applies the stylesheet to the ready XML document and outputs it.
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