XML Parsing With SAX and Xerces (part 2) - The Write Stuff
(Page 2 of 5 )
As in the first part of this article, we'll begin with something simple.
Let's go back to that XML file I created in the first part of this article:
<?xml version="1.0"?>
<inventory>
<item>
<id>758</id>
<name>Rusty,
jagged nails for nailgun</name>
<supplier>NailBarn, Inc.</supplier>
<cost>2.99</cost>
<quantity>10000</quantity>
</item>
<item>
<id>6273</id>
<name>Power
pack for death ray</name>
<supplier>QuakePower.domain.com</supplier>
<cost>9.99</cost>
<quantity>10</quantity>
</item>
</inventory>
Remember that event trail you saw in one of the very first examples? This next
example ports that code to work with a Web server.
import org.apache.xerces.parsers.SAXParser;
import org.xml.sax.*;
import org.xml.sax.helpers.DefaultHandler;
import
java.io.*;
public class MyFourthSaxApp extends DefaultHandler {
private Writer
out;
// constructor
public MyFourthSaxApp (String xmlFile, Writer out)
{
this.out = out;
// create a Xerces SAX parser
SAXParser parser = new SAXParser();
// set the content handler
parser.setContentHandler(this);
// parse the document
try {
parser.parse(xmlFile);
out.flush();
}
catch (SAXException e) {
// something went wrong!
} catch
(IOException e) {
// something went wrong!
}
}
//
call at document start
public void startDocument() {
try {
out.write
("<h1>Document
begins</h1><br>");
} catch (IOException e) {
//
do nothing
}
}
//
call at element start
public void startElement (String
uri, String local,
String qName,
Attributes atts) {
try {
out.write
("<h2>Element
begins: "" + local + ""</h2>");
String AttributeName,AttributeType,AttributeValue
= "";
for (int i = 0; i < atts.getLength(); i++) {
AttributeName =
atts.getLocalName(i);
AttributeType
= atts.getType(AttributeName);
AttributeValue
= atts.getValue(AttributeName);
out.write
("<h3>Attribute: "" + AttributeName
+ ""<br>");
out.write (" Type:
"" + AttributeType
+ ""<br>");
out.write (" Value:
"" + AttributeValue
+
""<br></h3>");
}
} catch (IOException
e) {
// do nothing
}
}
// call when cdata found
public void characters(char[]
text,
int start, int length) {
try {
String Content = new String(text, start,
length);
if (!Content.trim().equals("")){
out.write("<h4>Character
data: "" + Content + ""<br></h4>");
}
} catch (IOException e) {
//
do nothing
}
}
// call at element end
public void endElement (String
uri, String local, String qName){
try {
out.write("<h2> Element ends:
"" + local + ""<br></h2>");
} catch (IOException e) {
// do nothing
}
}
//
call at document end
public void endDocument() {
try {
out.write
("<h1>Document
ends</h1><br>");
} catch (IOException e) {
// do
nothing
}
}
}
I don't want to get into the details of the callbacks here - refer to the explanation
for the original example if there's something that doesn't seem to make sense - but I will point out some items of interest.
The most important difference between this example and the previous one is the introduction of a new Writer object, which makes it possible to stream output to the browser instead of the standard output device.
private Writer out;
The constructor also needs to be modified to accept two parameters: the name
of the XML file, and a reference to the Writer object.
// constructor
public MyFourthSaxApp (String xmlFile, Writer out) {
this.out
= out;
// constructor code comes here<sum>
}
This Writer object will be used to output HTML code to the browser, thereby enabling
the dynamic generation of a Web page - as the following snippets demonstrates:
out.write("<h2>Element begins: "" + local + ""</h2>");
out.write ("<h1>Document
ends</h1><br>");
Once this class has been compiled, it can easily be imported and used in a JSP
document, thereby immediately making the application Web-friendly.
Here's the code:
<%@ page language="java" import="java.io.IOException" %>
<html>
<head>
</head>
<body>
<%
try
{
MyFourthSaxApp myFourthExample = new
MyFourthSaxApp("/www/xerces/WEB-INF/classes/inventory.xml",out);
}
catch (Exception e) {
out.println("Something bad happened!");
}
%>
</body>
</html>
The output of this example is the HTML equivalent of the output of the previous
example. Here's what it looks like:
Next: Nailing It To The Wall >>
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