Data Overload - XML

Let's take a closer look at the printData() function:

private void printData (NodeList NodeCollection) throws SAXException {
try {
if (NodeCollection != null) {
for (int i=0; i< 
NodeCollection.getLength(); 
i++) {
local = NodeCollection.item(i).getNodeName();
if(local.equals("item")) {
// "item" element 
starts a new 
row
out.write("<tr>");
getElementData(NodeCollection.item(i));
printData(NodeCollection.item(i).getChildNodes());
out.write("</tr>");
} else if( local.equals("name") 
|| local.equals("supplier"))
{
// create table cells within 
row
// align strings left
out.write("<td><p 
align=left><font face=Verdana size=2>");
getElementData(NodeCollection.item(i));
printData(NodeCollection.item(i).getChildNodes());
out.write("</font></p></td>");
} else if( local.equals("id") 
|| local.equals("cost") ||
local.equals("quantity")) {
// create 
table cells within row
// align numbers right
out.write("<td><p 
align=right><font face=Verdana size=2>");
getElementData(NodeCollection.item(i));
printData(NodeCollection.item(i).getChildNodes());
out.write("</font></p></td>");
}
}
}
} catch (IOException e) {
throw new SAXException(e);
}
}

The printData() function maps different XML elements to appropriate HTML markup.

The different "item" elements correspond to rows within the table. The details of each item - name, supplier, quantity et al - are formatted as cells within each row of the table. Since Xerces represents this entire document as a tree, getting to each individual node involves moving between the different levels of the tree until a leaf, or terminal node, is encountered - which is why printData() utilizes the same recursive technique demonstrated in previous examples.

As stated earlier, for most of the elements, I'm simply displaying the content as is. The only deviation from this standard policy occurs with the "quantity" element, where an alert needs to be generated if the actual quantity falls below the minimum level. That's where the getElementData() function comes in - it contains code to test the current quantity against the minimum quantity, and highlight the data in red if the test fails. This function is quite complex, but the inline comments provided should help make it clearer.

private void getElementData(Node parentNode) throws SAXException {
try 
{
// get the type of the first child of the nodeset.
int childType 
= parentNode.getFirstChild().getNodeType();
// only proceed further 
if it is a text node
if (childType == Node.TEXT_NODE) {
// get the value stored at the node
String Content = parentNode.getFirstChild().getNodeValue();
// check for whitespace
// proceed only if non-empty string
if (!Content.trim().equals("")){
// check if node 
needs 
special handling (does the parent
node has attributes?)
if(parentNode.hasAttributes()) 
{
// if parent has attributes, 
this one needs special
handling
// first get the attributes
NamedNodeMap AttributesList 
= parentNode.getAttributes();
// iterate through the collection 
and get attribute
details
for(int j = 0; j < AttributesList.getLength(); 
j++) {
// element-specific attribute handling
if ( parentNode.getNodeName().equals("quantity") &&
AttributesList.item(j).getNodeName().equals("alert") 
) {
Quantity = new Integer(Content);
Alert = new
Integer(AttributesList.item(j).getNodeValue());
// if quantity lower than expected, highlight in red
if(Quantity.intValue() < Alert.intValue()) {
out.write("<font color="#ff0000">" + Quantity
+ "</font>");
} else {
out.write("<font 
color="#000000">" 
+ Quantity
+ "</font>");
}
} 
else     {
// element has attributes, 
but no special 
treatment
required
out.write(Content);
}
}
} else {
// parent 
node has no attributes
// just display the 
text
out.write(Content);
}
}
}
} catch 
(IOException e) {
throw new SAXException(e);
}
}

This function does a couple of different things. First, it checks to see if the node passed to it as an input parameter is a text node. If it is, the value of the node is checked, as is whether or not the parent node (the enclosing element) has any attributes. If no attributes are present and the node passes the whitespace test, the value is printed as is. In case the parent node *does* contain attributes, it must be either a "cost" or "quantity" element. If it's a "quantity" element, an additional test needs to be performed between the stated and alert quantities, with the resulting output highlighted on the basis of the test result.

With that out of the way, all that's left is to connect the class with the JSP page:

<%@ page language="java" import="java.io.IOException" %>
<html>
<head>
</head>
<body>
<h1><font 
face=Verdana>Inventory Management</font></h1>
<table width="55%" cellpadding="5" 
cellspacing="5" border="1">
<!-header row à
<tr>
<td><p align=right><b><font 
face=Verdana size=2> Code</font></b></p></td>
<td><b><font 
face=Verdana size=2>Name</font></b></td>
<td><b><font face=Verdana 
size=2>Supplier</font></b></td>
<td><p align=right><b><font 
face=Verdana size=2>Cost</font></b></p></td>
<td><p align=right><font 
face=Verdana size=2><b>Quantity</b></font></p></td>
</tr>
<%
try 
{
MyFifthDomApp myFifthExample = new
MyFifthDomApp("/www/xerces/WEB-INF/classes/inventory.xml",out);
} 
catch (Exception e) {
out.println("<font face="verdana" size="2">The 
following
error occurred: <br><b>" + e + "</b></font>");
}
%>
</table>
</body>
</html>

Here's what it looks like:

>>> More XML Articles          >>> More By icarus, (c) Melonfire

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