Zeus web server - Java & XML, 2nd Edition 15.1.3 Marshalling Marshalling
Java & XML, 2nd Edition 15.1.3 Marshalling Marshalling is just the opposite of unmarshalling. It is the process of converting a Java object and its dependent objects into an XML representation. In many cases, marshalling is part of a repeated cycle of transformations to and from XML, and is paired with unmarshalling. As an example, check out Figure 15-2, which is a typical application flow. Figure 15-2. XML data binding application flow There are two distinct ways to marshal a Java object. The first is to invoke a marshal( ) method on an object; this method is usually generated along with the accessors and mutators during class generation. The method recursively calls the marshal( ) method on each of its dependent objects, until you end up with an XML document. Note that the target XML document does not have to be the same as the original XML; you can easily end up with a vast number of archived XML documents by supplying different filenames to the marshalling process. A different approach to marshalling, and the one I favor, is having a standalone class that performs marshalling. Instead of invoking marshal( ) on a generated object, you invoke marshal( ) on the standalone class, and pass it the object to marshal. This is useful because it performs the same tasks as illustrated previously, but also allows classes that were not originally unmarshalled from XML to be converted to XML. Think about it this way: data binding, used like this, becomes a persistence framework. Any object with bean-like properties (setXXX( ) and getXXX( )) can easily be converted to XML! You get the power of data binding with the flexibility of persistence. This is a handy combination, and supported by some of the frameworks I talk about in this chapter. I realize that if you’re new to data binding, this may sound a bit confusing and vague; sort of like talking about chemistry. I’d much rather blow some things up (err. . . you know!), so in the rest of the chapter I show you how to use some data binding frameworks. Since I’m going to cover four of these, none of the examples are immensely complex; instead I focus on how
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