//SAXNodes.java
//Gerard Uffelman
//XMLJ Homework #2 Answer Key Example
import org.xml.sax.*;
import org.xml.sax.helpers.DefaultHandler;
import org.apache.xerces.parsers.SAXParser;
import java.io.FileOutputStream; //output file stream
import java.io.PrintStream; //FileOutputStream wrapper
import java.io.IOException; //catch user io errors
public class SAXNodes
{
public static void main(String[] args)
{
FileOutputStream fos;
PrintStream ps;
int nodeSize = 0;
//Check input parameters
if(args.length <= 2 || args.length > 3)
{
System.err.println("Invalid Command: Wrong number of arguments!");
System.err.println("Usage:\tjava SaxNodes graphFile nodeSize outputFile");
System.exit(0);
}
//Get maximum page size from input
try{
Integer intWrapper = new Integer( args[1] );
nodeSize = intWrapper.intValue();
}
catch(NumberFormatException nfe)
{
System.err.println("Error, invalid number: " + args[1]);
return;
}
//Try to open file for output
try{
fos = new FileOutputStream( args[2] );
}
catch(IOException ioe)
{
System.err.println("Can't open output file: " + args[2]);
return;
}
//Instantiate ps with fos
ps = new PrintStream(fos);
//Create NodeHandler class to handle SAX events and parse
//input file.
try{
NodeHandler handler = new NodeHandler(ps, nodeSize);
SAXParser parser = new SAXParser();
parser.setContentHandler(handler);
parser.setErrorHandler(handler);
parser.parse(args[0]);
}
catch(Exception e){
e.printStackTrace(System.err);
}
ps.close(); //Close PrintStream
}
}
//This class extends DefaultHandler and handles SAX events for us.
//NodeHandler overloads startElement, startDocument, and endDocument from
//DefaultHandler
class NodeHandler extends DefaultHandler
{
PrintStream ps;
int nodeSize;
//Constructor takes reference to a printStram and nodeSize value
public NodeHandler(PrintStream ps_in, int nodeSize_in)
{
nodeSize = nodeSize_in;
if(ps_in != null)
ps = ps_in;
else
System.err.println("Output PrintStream is null");
}
//Write the following to our output file when the startDocument event occurs.
public void startDocument()
{
ps.println("");
ps.println("");
ps.println("Report of Nodes with size greater than " + nodeSize + " ");
ps.println("");
ps.println("");
ps.println("Node Report by size:\n
");
ps.println("
");
ps.println("");
}
//Write the following to our output file when the endDocument event occurs.
public void endDocument()
{
ps.println("
");
ps.println("");
ps.println("");
}
//Every time we encounter the start of a new element, check to see if it is a
//node element.
public void startElement(String uri, String localName, String rawName, Attributes attributes)
{
if(localName.equals("node"))
{
//get node information
String weight = attributes.getValue("weight");
Integer wWrapper = new Integer(weight);
int size = wWrapper.intValue();
String label = attributes.getValue("label");
String id = attributes.getValue("id");
//if the nodes is the right size, write its info to the output file.
if(size > nodeSize )
{
if(label != null)
{
ps.println(" Node ID: " + id + "
\n" +
" " + label +
"
\n Size: " + size + "");
}
else
{
ps.println(" Node ID: " + id + "
\n" +
"
\n Size: " + size + "");
}
}
}
}//end startElement()
}//end class NodeHandler