Tutorials : Converting XML documents to Java objects with Castor XML :

The way Castor XML works

In order for Castor to convert between XML documents and Java objects, it needs "mapping information" which can be obtained from several sources:

• through introspection of classes
• from a mapping file (XML-format)
• from class descriptors

 The first possibility alone is only an option in simple situations. Normally you'd need to tell Castor how XML-elements and Java-classes should be mapped, and this is done using a mapping file in XML-format.  

Here is a very small example: Assume that you have a class called demo.Person with instance variables called occupation and lastName, and an XML-document containing:

. . . 
<person occupation="programmer">
  <lastname>Gosling</lastname>
</person>
. . . 

A Castor mapping file that will match this document to the Person class is this:  

. . .
<class name="demo.Person">
  <map-to xml="person"/>
  <field name="occupation" type="string">
    <bind-xml name="occupation" node="attribute"/>
  </field>
  <field name="lastName" type="string">
    <bind-xml name="lastname" node="element"/>
  </field>
</class>
. . .

The class- and field-elements refer to the Java class, and the map-to- and bind-xml-elements to the XML-document.  

I won't go into details about how to construct the mapping file--there are several very good articles on the web giving examples on this, and I've listed some of the best in the resources section at the end of the article. Instead we'll start looking at the third mapping option using class descriptors.  

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