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Java Tip 138: Still parsing to generate your JavaBeans' XML representation?

Delegate this job to a JavaBean-XML mapping component

By Paulo Caroli, JavaWorld.com, 05/09/03

By using Remote Method Invocation (RMI) in distributed Java application development, no low-level socket or network communication code is involved. The code remains at a higher level, leveraging its use of RMI classes. Similar gain comes with the use of Enterprise JavaBeans (EJB) technology, freeing developers from several low-level coding aspects (transaction, recovery, and activation). With this tip's JavaBean-XML mapping component, developers don't directly deal with XML-related APIs.

Note: You can download this tip's source code from Resources.

Write the component

The BeanXMLMapping component converts a JavaBean to an XML document and vice versa. By using JavaBean introspection, XML parsers, and DOM APIs, you can develop this component with a toXML() method to represent the received bean as an XML document and a fromXML() method to instantiate and populate the proper bean according to the XML document received.

Listing 1 shows a possible implementation for the BeanXMLMapping component. This particular implementation uses the JOX (Java Objects in XML) library. You can develop other implementations of this component using other APIs. I selected JOX for its simple, reusable solution.

Listing 1. BeanXMLMapping component

import com.wutka.jox.*;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class BeanXMLMapping {
  /**
   *  Retrieves a bean object for the
   *  received XML and matching bean class
   */
  public static Object fromXML(String xml, Class className) {
    ByteArrayInputStream xmlData = new ByteArrayInputStream(xml.getBytes());
    JOXBeanInputStream joxIn = new JOXBeanInputStream(xmlData);
    try {
      return (Object) joxIn.readObject(className);
    } catch (IOException exc) {
      exc.printStackTrace();
      return null;
    } finally {
      try {
        xmlData.close();
        joxIn.close();
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
  /**
   *  Returns an XML document String for the received bean
   */
  public static String toXML(Object bean) {
    ByteArrayOutputStream xmlData = new ByteArrayOutputStream();
    JOXBeanOutputStream joxOut = new JOXBeanOutputStream(xmlData);
    try {
      joxOut.writeObject(beanName(bean), bean);
      return xmlData.toString();
    } catch (IOException exc) {
      exc.printStackTrace();
      return null;
    } finally {
      try {
        xmlData.close();
        joxOut.close();
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
  /**
   *  Find out the bean class name
   */
  private static String beanName(Object bean) {
    String fullClassName = bean.getClass().getName();
    String classNameTemp = fullClassName.substring(
        fullClassName.lastIndexOf(".") + 1,
        fullClassName.length()
        );
    return classNameTemp.substring(0, 1)
         + classNameTemp.substring(1);
  }
}

The BeanXMLMapping class converts a JavaBean to and from an XML document and provides two methods: