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XML JavaBeans, Part 3

Integrate the XMLBeans package with the Java core

By Mark Johnson, JavaWorld.com, 07/24/99

After a hiatus of three months, this article completes the three-part series on the XMLBeans package. Simply put, XMLBeans can transform a JavaBean in memory into an XML document, or can transform an XML document (of a particular form) into a running JavaBean. Figure 1 shows an extremely simplified schematic of the concept.

Figure 1. The XMLBeans package

If you've experimented with XML and JavaBeans in this series, you'll have noticed that the XMLBeanWriter class we created in Part 2 is capable of creating XMLBeans XML files that the XMLBeanReader from Part 1 can't read. Some readers have also noted that the XMLBeans file format is somewhat complicated, and that controlling which properties are encoded in XML and which properties are ignored requires a lot of tedious coding. This month, we'll solve these problems by restructuring the XMLBeanReader and XMLBeanWriter classes. In the process, we'll simplify the file format while maintaining backward compatibility. Perhaps most interestingly, we'll simplify and generalize controlling XMLBeans properties by integrating XMLBeans with the core java.beans package.

Background reading

This article covers some intermediate-to-advanced JavaBeans topics, so you may need to do some background reading to get up to speed. The links to the articles described here appear in the Resources section.

TEXTBOX:

TEXTBOX_HEAD: XML JavaBeans: Read the whole series!

• Part 1. Make JavaBeans mobile and interoperable with XML
  
  

• Part 2. Automatically convert JavaBeans to XML documents
  
  

• Part 3. Integrate the XMLBeans package with the Java core
  
  

:END_TEXTBOX

First, I assume you've read and understand the first two articles (Parts 1 and 2) in this series. If you haven't read these articles, this month's article may not make much sense to you.

If you're new to XML, you might consider reading "XML for the absolute beginner," (JavaWorld April 1999). This article discusses JavaBeans property descriptors, property editor classes, and BeanInfo objects, topics previously covered in "The trick to controlling bean customization," and "Soup up your Java classes with customization." Once you have a passing understanding of these subjects, you'll be ready to tackle this final installment of the XML JavaBeans series.

As always, I shortened the code listings in this article by putting the code section under discussion into a scrolling list box. Since some readers dislike this convention, each code listing's caption includes a hyperlink to a printable HTML file. You can pop open a new browser and scroll this complete listing, if you'd like, or you can print the file and follow along on paper.

Improving XMLBeans

I find software to be in some ways like art: in practically every instance, as soon as I've completed a project, I'm aware of my work's weaknesses and how it could have been done better. The code we're going to discuss is a second attempt at creating an interface to read and write JavaBeans objects as XML documents. We won't spend a lot of time discussing the weaknesses of the previous design, but you'll see as we go along that the new implementation is cleaner and more flexible than the original.

 

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