SAX Java problem

Question

Hi,
This is my first time to your forum. I would be grateteful if some one could tell me where Im going wrong.
My program use a SAX parser in a Java application. It should read an XML file and extract cetain attibutes if they appear.
Here is the program.
import java.io.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
import javax.xml.parsers.*;
public class PacketValues extends DefaultHandler {
public static void main(String[] arguments) {
if (arguments.length ==1) {
PacketValues pv = new PacketValues(arguments[0]);
} else {
System.out.println("input just the xml file please");
PacketValues(String xmlFile) {
File input = new File(xmlFile);
SAXParserFactory factory = SAXParserFactory.newInstance();
factory.setValidating(false);
try {
SAXParser sax = factory.newSAXParser();
PacketValueProcessor pvp = new PacketValueProcessor();
sax.parse(input, pvp);
System.out.println("The value is " + pvp.a);
} catch (ParserConfigurationException pce) {
System.out.println("Could not create that parser. ");
System.out.println(pce.getMessage());
} catch (SAXException se) {
System.out.println("Problem with the SAX parser. ");
System.out.println(se.getMessage());
} catch (IOException ioe) {
System.out.println("Error reading file.");
System.out.println(ioe.getMessage());
class PacketValueProcessor extends DefaultHandler {
String a;
PacketValueProcessor() {
super();
public void startElement(String URI, String localName,
String qName, Attributes atts) {
System.out.println("here in startElement");
if (localName.equals("field")) {
System.out.println("localname equals field");
String n = atts.getValue("","name");
System.out.println("n is " + n);
if (n.equals("timestamp")) {
String a = atts.getValue("","value");
System.out.println("a is " + a);
if (n.equals("tcp.seq")) {
String a = atts.getValue("","value");
System.out.println("a is " + a);
It aims to extract both the value of a field element which has a name attribute "timestamp" and the value of a field element which has the attribute "tcp.seq".
Here is part of the xml file
<?xml version="1.0"?>
<pdml version="0" creator="ethereal/0.10.0">
<packet>
<proto name="geninfo" pos="0" showname="General information" size="74">
<field name="num" pos="0" show="1" showname="Number" value="1" size="74"/>
<field name="len" pos="0" show="74" showname="Packet Length" value="4a" size="74"/>
<field name="caplen" pos="0" show="74" showname="Captured Length" value="4a" size="74"/>
<field name="timestamp" pos="0" show="Jan 22, 2004 12:04:58.646896000" showname="Captured Time" value="1074773098.646896000" size="74"/>
</proto>
<proto name="frame" showname="Frame 1 (74 bytes on wire, 74 bytes captured)" size="74" pos="0">
<field name="frame.marked" showname="Frame is marked: False" size="0" pos="0" show="0"/>
<field name="frame.time" showname="Arrival Time: Jan 22, 2004 12:04:58.646896000" size="0" pos="0" show="Jan 22, 2004 12:04:58.646896000"/>
<field name="frame.time_delta" showname="Time delta from previous packet: 0.000000000 seconds" size="0" pos="0" show="0.000000000"/>
<field name="frame.time_relative" showname="Time since reference or first frame: 0.000000000 seconds" size="0" pos="0" show="0.000000000"/>
<field name="frame.number" showname="Frame Number: 1" size="0" pos="0" show="1"/>
<field name="frame.pkt_len" showname="Packet Length: 74 bytes" size="0" pos="0" show="74"/>
<field name="frame.cap_len" showname="Capture Length: 74 bytes" size="0" pos="0" show="74"/>
</proto>
<proto name="eth" showname="Ethernet II, Src: 00:05:5d:6d:a0:87, Dst: 00:50:da:4f:6d:83" size="14" pos="0">
<field name="eth.dst" showname="Destination: 00:50:da:4f:6d:83 (3com_4f:6d:83)" size="6" pos="0" show="00:50:da:4f:6d:83" value="0050da4f6d83"/>
<field name="eth.src" showname="Source: 00:05:5d:6d:a0:87 (D-Link_6d:a0:87)" size="6" pos="6" show="00:05:5d:6d:a0:87" value="00055d6da087"/>
<field name="eth.addr" showname="Source or Destination Address: 00:50:da:4f:6d:83 (3com_4f:6d:83)" size="6" pos="0" show="00:50:da:4f:6d:83" value="0050da4f6d83"/>
<field name="eth.addr" showname="Source or Destination Address: 00:05:5d:6d:a0:87 (D-Link_6d:a0:87)" size="6" pos="6" show="00:05:5d:6d:a0:87" value="00055d6da087"/>
<field name="eth.type" showname="Type: IP (0x0800)" size="2" pos="12" show="0x0800" value="0800"/>
</proto>
<proto name="ip" showname="Internet Protocol, Src Addr: 192.168.2.21 (192.168.2.21), Dst Addr: 192.168.3.10 (192.168.3.10)" size="20" pos="14">
<field name="ip.version" showname="Version: 4" size="1" pos="14" show="4" value="45"/>
<field name="ip.hdr_len" showname="Header length: 20 bytes" size="1" pos="14" show="20" value="45"/>
<field name="ip.dsfield" showname="Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)" size="1" pos="15" show="0" value="00">
<field name="ip.dsfield.dscp" showname="0000 00.. = Differentiated Services Codepoint: Default (0x00)" size="1" pos="15" show="0x00" value="00"/>
<field name="ip.dsfield.ect" showname=".... ..0. = ECN-Capable Transport (ECT): 0" size="1" pos="15" show="0" value="00"/>
<field name="ip.dsfield.ce" showname=".... ...0 = ECN-CE: 0" size="1" pos="15" show="0" value="00"/>
</field>
<field name="ip.len" showname="Total Length: 60" size="2" pos="16" show="60" value="003c"/>
<field name="ip.id" showname="Identification: 0xd779 (55161)" size="2" pos="18" show="0xd779" value="d779"/>
<field name="ip.flags" showname="Flags: 0x04" size="1" pos="20" show="0x04" value="40">
<field name="ip.flags.df" showname=".1.. = Don't fragment: Set" size="1" pos="20" show="1" value="40"/>
<field name="ip.flags.mf" showname="..0. = More fragments: Not set" size="1" pos="20" show="0" value="40"/>
</field>
<field name="ip.frag_offset" showname="Fragment offset: 0" size="2" pos="20" show="0" value="4000"/>
<field name="ip.ttl" showname="Time to live: 64" size="1" pos="22" show="64" value="40"/>
<field name="ip.proto" showname="Protocol: TCP (0x06)" size="1" pos="23" show="0x06" value="06"/>
<field name="ip.checksum" showname="Header checksum: 0xdcd2 (correct)" size="2" pos="24" show="0xdcd2" value="dcd2"/>
<field name="ip.src" showname="Source: 192.168.2.21 (192.168.2.21)" size="4" pos="26" show="192.168.2.21" value="c0a80215"/>
<field name="ip.addr" showname="Source or Destination Address: 192.168.2.21 (192.168.2.21)" size="4" pos="26" show="192.168.2.21" value="c0a80215"/>
<field name="ip.dst" showname="Destination: 192.168.3.10 (192.168.3.10)" size="4" pos="30" show="192.168.3.10" value="c0a8030a"/>
<field name="ip.addr" showname="Source or Destination Address: 192.168.3.10 (192.168.3.10)" size="4" pos="30" show="192.168.3.10" value="c0a8030a"/>
</proto>
<proto name="tcp" showname="Transmission Control Protocol, Src Port: 32862 (32862), Dst Port: 5001 (5001), Seq: 0, Ack: 0, Len: 0" size="40" pos="34">
<field name="tcp.srcport" showname="Source port: 32862 (32862)" size="2" pos="34" show="32862" value="805e"/>
<field name="tcp.dstport" showname="Destination port: 5001 (5001)" size="2" pos="36" show="5001" value="1389"/>
<field name="tcp.port" showname="Source or Destination Port: 32862" size="2" pos="34" show="32862" value="805e"/>
<field name="tcp.port" showname="Source or Destination Port: 5001" size="2" pos="36" show="5001" value="1389"/>
<field name="tcp.len" showname="TCP Segment Len: 0" size="4" pos="34" show="0" value="805e1389"/>
<field name="tcp.seq" showname="Sequence number: 0" size="4" pos="38" show="0" value="8dc936ab"/>
<field name="tcp.hdr_len" showname="Header length: 40 bytes" size="1" pos="46" show="40" value="a0"/>
<field name="tcp.flags" showname="Flags: 0x0002 (SYN)" size="1" pos="47" show="0x02" value="02">
<field name="tcp.flags.cwr" showname="0... .... = Congestion Window Reduced (CWR): Not set" size="1" pos="47" show="0" value="02"/>
<field name="tcp.flags.ecn" showname=".0.. .... = ECN-Echo: Not set" size="1" pos="47" show="0" value="02"/>
<field name="tcp.flags.urg" showname="..0. .... = Urgent: Not set" size="1" pos="47" show="0" value="02"/>
<field name="tcp.flags.ack" showname= etc etc
The output is
here in startElement
here in startElement
here in startElement
here in startElement
here in startElement
here in startElement
here in startElement
here in startElement
etc
etc
here in startElement
here in startElement
The value is null
this of course means that all the program gets as far as startElement
it never gets beyond the condition
if (localName.equals("field")) {
Can someone tell me why? Im not an experienced programmer.
Thanks in advance.

Answer 1

I based my program on this program:
import java.io.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
import org.apache.xerces.parsers.SAXParser;
public class Flour extends DefaultHandler {
float amount = 0;
public void startElement(String namespaceURI, String localName,
String qName, Attributes atts) {
if (namespaceURI.equals("http://recipes.org") && localName.equals("ingredient")) {
String n = atts.getValue("","name");
if (n.equals("flour")) {
String a = atts.getValue("","amount"); // assume 'amount' exists
amount = amount + Float.valueOf(a).floatValue();
public static void main(String[] args) {
Flour f = new Flour();
SAXParser p = new SAXParser();
p.setContentHandler(f);
try { p.parse(args[0]); }
catch (Exception e) {e.printStackTrace();}
System.out.println(f.amount);
which has as the data
<?xml version="1.0" encoding="UTF-8" ?>
<?dsd href="recipes.dsd"?>
- <collection xmlns="http://recipes.org" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://recipes.org recipes.xsd">
<description>Some recipes used in the XML tutorial.</description>
- <recipe>
<title>Beef Parmesan with Garlic Angel Hair Pasta</title>
<ingredient name="beef cube steak" amount="1.5" unit="pound" />
<ingredient name="onion, sliced into thin rings" amount="1" />
<ingredient name="green bell pepper, sliced in rings" amount="1" />
<ingredient name="Italian seasoned bread crumbs" amount="1" unit="cup" />
<ingredient name="grated Parmesan cheese" amount="0.5" unit="cup" />
<ingredient name="olive oil" amount="2" unit="tablespoon" />
<ingredient name="spaghetti sauce" amount="1" unit="jar" />
<ingredient name="shredded mozzarella cheese" amount="0.5" unit="cup" />
<ingredient name="angel hair pasta" amount="12" unit="ounce" />
<ingredient name="minced garlic" amount="2" unit="teaspoon" />
<ingredient name="butter" amount="0.25" unit="cup" />
- <preparation>
<step>Preheat oven to 350 degrees F (175 degrees C).</step>
<step>Cut cube steak into serving size pieces. Coat meat with the bread crumbs and parmesan cheese. Heat olive oil in a large frying pan, and saute 1 teaspoon of the garlic for 3 minutes. Quick fry (brown quickly on both sides) meat. Place meat in a casserole baking dish, slightly overlapping edges. Place onion rings and peppers on top of meat, and pour marinara sauce over all.</step>
<step>Bake at 350 degrees F (175 degrees C) for 30 to 45 minutes, depending on the thickness of the meat. Sprinkle mozzarella over meat and leave in the oven till bubbly.</step>
<step>Boil pasta al dente. Drain, and toss in butter and 1 teaspoon garlic. For a stronger garlic taste, season with garlic powder. Top with grated parmesan and parsley for color. Serve meat and sauce atop a mound of pasta!</step>
</preparation>
my program doesnt need to account for namespaces apart from that I cant see why this would work and my one not.