Java Enterprise Best Practices

Don’t Be Afraid to Use Helper Classes

This is more of a general tip for working with DOM, but it still certainly belongs in the category of best practices. When working with the DOM, you should always write yourself a suite of helper classes, or at least look around for existing suites.

I have several versions of helper classes floating around my development environments at any given time, usually with names such as DOMHelper, DOMUtil, or some other permutation. I’ve omitted many of these from this chapter, as the methods in those classes are specific to the kinds of DOM manipulation I perform, which are likely different from the kinds of DOM manipulation you will perform. If, for example, you often need to walk trees, you may want a method such as the one shown in Example 5-12 to easily obtain the text of a node.

Example 5-12. Helper class for walking DOM trees

// Get the text of a node without the extra TEXT node steps.
   
public static String getText(Node node) {
   
    // Make sure this is an element.
   
    if (node instanceof Element) {
   
        // Make sure there are children.
   
        if (node.hasChildNodes(  )) {
   
            StringBuffer text = new StringBuffer(  );
            NodeList children = node.getChildNodes(  );
            for (int i=0; i<children.getLength(  ); i++) {
                Node child = children.item(i);
                if (child.getNodeType(  ) =  = Node.TEXT_NODE) {
                    text.append(child.getNodeValue(  ));
                }
            }
            return text.toString(  );
        } else {
            return null;
        }
    } else {
        return null;
    }
}

This is one of two types of methods that retrieve the text of an element. This ...