Highlights - XML

Now, how about something a little more useful? Let's suppose I want to display this same information in a neatly-formatted table, with those items that I'm low on highlighted in red. My preferred output would look something like this:



Here's the code to accomplish this:

import org.apache.xerces.parsers.DOMParser;
import org.xml.sax.SAXException;
import 
org.w3c.dom.*;
import java.io.*;
public class MyFifthDomApp {
private Writer 
out;
private String local = "";
private Integer Alert, Quantity;
// constructor
public MyFifthDomApp (String xmlFile, Writer out) throws 
SAXException
{
this.out = out;
// create a Xerces DOM parser
DOMParser parser = new DOMParser();
// parse the document
// get to the root node's children
// call a recursive function 
to process the tree
try {
parser.parse(xmlFile);
Document document = parser.getDocument();
Element 
RootElement = document.getDocumentElement();
NodeList Children 
= RootElement.getChildNodes();
printData(Children);
out.flush();
} catch (IOException e) {
throw new SAXException(e);
}
}
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);
}
}
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);
}
}
}

Before you consider diving out of your window to escape the squiggles above, you might want to read the explanation - it's nowhere near as complicated as it looks.

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, which has an additional "alert" attribute. This "alert" attribute specifies the minimum number of items that should be in stock of the corresponding item; if the quantity drops below this minimum level, an alert should be generated.

With this in mind, I've designed the class above around two main functions, one to traverse the document tree and the other to actually print the content it finds. And so, I have the printData() function, which recursively processes the document tree, and the getElementData() function, which retrieves the data enclosed with the XML elements.

Let's take a closer look at the different elements of the listing above:

// constructor
public MyFifthDomApp (String xmlFile, Writer out) throws SAXException 
{
this.out = out;
// create a Xerces DOM parser
DOMParser 
parser 
= new DOMParser();
//  parse the document
//  get to the 
root node's 
children
// call a recursive function to process the tree
try {
parser.parse(xmlFile);
Document document = parser.getDocument();
Element RootElement = document.getDocumentElement();
NodeList 
Children = RootElement.getChildNodes();
printData(Children);
out.flush();
} catch (IOException e) {
throw new SAXException(e);
}
}

If you look at this closely, you'll see that I've been holding out on you a little in the previous examples. I never told you about the getDocumentElement() method, which lets you immediately access the document (outermost) element of the XML document. Well, now you know.

Once a reference to the document element has been obtained, the nest step is to obtain a list of its children, and hand these over to printData() for processing.

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

blog comments powered by Disqus