Cure Your Java XML Troubles with a Dose of Castor Oil

Now you're ready to generate some XML. As before, you read the mapping file in, but this time you create a Marshaller, handing it a java.io.Writer (in this case a StringWriter, that will store the XML for us to print.) Then you have only to set the mapping on the marshaller, and marshall the top-level object, in this case our book collection.

        Mapping mapping = new Mapping();
        InputStream mappingStream =
            Example3.class.
           getResourceAsStream("collection-mapping.xml");
        mapping.loadMapping(new InputSource(mappingStream));
                            
        Writer stringWriter = new StringWriter();
            
        Marshaller marshaller = new Marshaller(stringWriter);
        marshaller.setMapping(mapping);
        marshaller.marshal(col);
        stringWriter.close();
        System.out.println(stringWriter.toString());
    } catch (MarshalException e) {
        e.printStackTrace();
    } catch (ValidationException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (MappingException e) {
        e.printStackTrace();
    }
}

The resulting XML looks just like you want it:

<?xml version="1.0" encoding="UTF-8"?>
<collection>
	<book isbn="0672323095">
		<title>MySQL and JSP Web Applications</title>
		<author>
			<lastname>Turner</lastname>
			<firstname>James</firstname>
		</author>
	</book>
	<book isbn="0672324725">
		<title>Struts Kick Start</title>
		<author>
			<lastname>Bedell</lastname>
			<firstname>Kevin</firstname>
		</author>
		<author>
			<lastname>Turner</lastname>
			<firstname>James</firstname>
		</author>
	</book>
</collection>

This article only begins to scratch the surface of what Castor can do, a particularly good walkthrough of how to use mapping files with Castor can be found at: http://www.castor.org/xml-mapping.html.

About the Author

James Turner is a Senior Software Engineer at Kronos, Inc. He has written two books on Java Web Development and writes frequently on technology and software development.

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