How to synchronize Serial communication?

My function is checking on work attendance with IC Card :
1. Read Serial, get IC cardno
2. check cardno, query cardno from database
3. if cardno is valid, send "S98" to serial, otherwise send "S97"
4. Save cardno and current time to database

My program is often running corret, but sometimes do absurdness things. For example, my ic cardno is 10 chars, but sometimes only get first 8 chars.
[ August 11, 2004: Message edited by: chen leon ]

my program is :
SerailValidator.validBytes() is XOR validation the data
CardManager.isCardValid() is query the cardno from database
CardManager.saveCardRecord() is execute an insert SQL.

package com.ditian.serial;

import javax.servlet.ServletContextListener;
import javax.servlet.ServletContextEvent;
import java.io.*;
import java.util.*;
import javax.comm.*;

public class SerialTerminal implements SerialPortEventListener, Runnable {
private InputStream in = null;
private OutputStream out = null;
private SerialPort serialPort = null;

public static final String ValidStr = "S98";
public static final String InvalidStr = "S97";

public static void main(String[] args) throws IOException {
SerialTerminal term = new SerialTerminal(args.length > 0 ? args[0]
: null);
}

public SerialTerminal(String port) {
System.out.println("serail termina init...............");
if (port == null) {
port = "COM2";
}
CommPortIdentifier portId = null;
System.out.println("Searching for port: " + port);
Enumeration portList = CommPortIdentifier.getPortIdentifiers();
while (portList.hasMoreElements()) {
CommPortIdentifier cpi = (CommPortIdentifier) portList
.nextElement();
if (cpi.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (cpi.getName().equals(port)) {
System.out.println("Found port: " + cpi.getName());
portId = cpi;
break;
}
}
}
if (portId == null) {
System.out.println("port " + port + " not found.");
}
try {
serialPort = (SerialPort) portId.open("SimpleReadApp", 2000);
serialPort.setSerialPortParams(9600, SerialPort.DATABITS_8,
SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
//serialPort.enableReceiveTimeout(2000);

serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
serialPort.notifyOnCTS(true);
serialPort.notifyOnDSR(true);
serialPort.notifyOnRingIndicator(true);
serialPort.notifyOnCarrierDetect(true);
serialPort.notifyOnOverrunError(true);
serialPort.notifyOnParityError(true);
serialPort.notifyOnFramingError(true);
serialPort.notifyOnBreakInterrupt(true);
//serialPort.notifyOnDataAvailable(true);
serialPort.notifyOnOutputEmpty(true);

in = serialPort.getInputStream();
out = serialPort.getOutputStream();

OutputStream out = serialPort.getOutputStream();
} catch (PortInUseException e) {
System.out.println("Port " + port + " is in use.");
} catch (Exception e) {
e.printStackTrace(System.out);
}
}
public void close() {
try {
in.close();
out.close();
serialPort.close();
} catch (Exception e) {
e.printStackTrace();
}
}
//implement Runnable
public void run() {
try
{
synchronized (this) {
wait(10000);
}
}
catch (InterruptedException e)
{
}

if (this.DA) {
readData();
notifyAll();
}
}

public void serialEvent(SerialPortEvent event) {
switch (event.getEventType()) {
case SerialPortEvent.BI:
case SerialPortEvent.OE:
case SerialPortEvent.FE:
case SerialPortEvent.PE:
case SerialPortEvent.CD:
case SerialPortEvent.CTS:
case SerialPortEvent.DSR:
case SerialPortEvent.RI:
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
break;
case SerialPortEvent.DATA_AVAILABLE:
this.DA = true;
readData();
try {
wait(5000);
} catch (Exception e){
}
notifyAll();
break;
}
}

private boolean DA;

synchronized private void readData() {
if (!DA) return;

byte[] buf = new byte[12];
int r = 0;
try {
while ((r = in.read(buf)) != -1) {
System.out.println("IN: " + new String(buf, 0, r));
//validation received data
boolean bb = false;

bb = SerailValidator.validBytes(buf);
String cardNo = "";
if (bb) {
cardNo = new String(buf, 0, r - 1);
// validation card
bb = CardManager.isCardValid(cardNo);
}
//try {Thread.sleep(50);} catch (Exception e) {}
if (bb) {
System.out.println("valid");
for (int k = 0; k < ValidStr.length(); k++) {
out.write(ValidStr.charAt(k));
}
try {Thread.sleep(100);} catch (Exception e) {}
} else {
System.out.println("invalid");
for (int k = 0; k < InvalidStr.length(); k++) {
out.write(InvalidStr.charAt(k));
}
}
//save card record
if (bb) CardManager.saveCardRecord(cardNo);

}
} catch (IOException e) {
System.err.println("ERR: " + e.getMessage());
}
this.DA = false;
notifyAll();
}
}
[ August 11, 2004: Message edited by: chen leon ]

My programm is often corret, but sometimes do absurdness things.

Life is full of surprises and absurd things, isn't it?
Sometimes even a card number may not be read correctly.

How about adding #5 to your spec:
5. if attempt to read a card number failed, then do something to address the issue

I have run some sun javacomm samples.

"BlackBox" is good.
"Simple" is the same with my program, sometimes occur error.
Why?
Is it a synchronization problem?

I follow James Bacon's topic, modify my program, but the error is exits.

public void run() {
try {
synchronized (this) {
wait(10000);
}
} catch (InterruptedException e) {
}
if (this.DA) {
//readData();
}
}

public void serialEvent(SerialPortEvent event) {
switch (event.getEventType()) {
case SerialPortEvent.BI:
case SerialPortEvent.OE:
case SerialPortEvent.FE:
case SerialPortEvent.PE:
case SerialPortEvent.CD:
case SerialPortEvent.CTS:
case SerialPortEvent.DSR:
case SerialPortEvent.RI:
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
break;
case SerialPortEvent.DATA_AVAILABLE:
while (this.DA) {
try {
wait();
} catch (InterruptedException e) {
}
}
//synchronized (lock) {
this.DA = true;
readData();
//}
break;
}
}

private boolean DA;

synchronized private void readData() {
while (!this.DA) {
try {
wait();
} catch (InterruptedException e) {
}
}

//synchronized (lock) {
byte[] buf = new byte[12];
int r = 0;
try {
while ((r = in.read(buf)) != -1) {
System.out.println("IN: " + new String(buf, 0, r));
//validation received data
boolean bb = false;

bb = SerailValidator.validBytes(buf);
String cardNo = "";
if (bb) {
cardNo = new String(buf, 0, r - 1);
// validation card
bb = CardManager.isCardValid(cardNo);
}

if (bb) {
System.out.println("valid");
for (int k = 0; k < ValidStr.length(); k++) {
out.write(ValidStr.charAt(k));
}
} else {
System.out.println("invalid");
for (int k = 0; k < InvalidStr.length(); k++) {
out.write(InvalidStr.charAt(k));
}
}
//save card record
if (bb)
CardManager.saveCardRecord(cardNo);
}
} catch (IOException e) {
System.err.println("ERR: " + e.getMessage());
}
this.DA = false;
notifyAll();
//}
}