XML Parsing With DOM and Xerces (part 2) - Data Overload (
Page 4 of 9 )
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:
