[求助]关于eclipse下开发串口操作插件的问题

请教一下,我用eclipse开发一个可以读取串口信息的插件,把它单独作为应用程序可以正常运行.但以插件形式运行时点击按钮就会出现
Unhandled event loop exception
Reason:
javax/comm/NoSuchPortException异常.不知道是什么问题?
插件窗口程序:
package com.plugin.Hello;
import org.eclipse.core.runtime.*;
import org.eclipse.jface.dialogs.ErrorDialog;
import org.eclipse.jface.window.ApplicationWindow;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;
import com.leon.serial.*;
/**
* This class demonstrates JFace's ErrorDialog class
*/
public class DialogSample extends ApplicationWindow {
/**
* ShowError constructor
*/
public DialogSample() {
super(null);
}
/**
* Runs the application
*/
public void run() {
// Don't return from open() until window closes
setBlockOnOpen(true);
// Open the main window
open();
// Dispose the display
Display.getCurrent().dispose();
}
/**
* Configures the shell
*
* @param shell the shell
*/
protected void configureShell(Shell shell) {
super.configureShell(shell);
// Set the title bar text and the size
shell.setText("read com");
shell.setSize(400, 400);
}
/**
* Creates the main window's contents
*
* @param parent the main window
* @return Control
*/
protected Control createContents(Composite parent) {
Composite composite = new Composite(parent, SWT.NONE);
composite.setLayout(new GridLayout(1, false));
// Create a big text box to accept error text
final Text text = new Text(composite, SWT.MULTI | SWT.BORDER | SWT.V_SCROLL);
text.setLayoutData(new GridData(GridData.FILL_BOTH));
// Create the button to launch the error dialog
Button show = new Button(composite, SWT.PUSH);
show.setText("open serial port");
show.addSelectionListener(new SelectionAdapter() {
public void widgetSelected(SelectionEvent event) {
SerialBean SB = new SerialBean(2);
String Msg = "";
SB.Initialize();

Msg = SB.ReadPort(10);
SB.ClosePort();
text.setText(Msg);
}
});
return composite;
}
/**
* The application entry point
*
* @param args the command line arguments
*/
/* public static void main(String[] args) {
new DialogSample().run();
}
*/
}

插件是根据helloworld改过来的
package com.plugin.Hello;
import org.eclipse.ui.plugin.*;
import org.osgi.framework.BundleContext;
import java.util.*;
/**
* The main plugin class to be used in the desktop.
*/
public class HelloPlugin extends AbstractUIPlugin {
//The shared instance.
private static HelloPlugin plugin;
//Resource bundle.
private ResourceBundle resourceBundle;

/**
* The constructor.
*/
public HelloPlugin() {
super();
plugin = this;
try {
resourceBundle = ResourceBundle.getBundle("com.plugin.Hello.HelloPluginResources");
} catch (MissingResourceException x) {
resourceBundle = null;
}
}
/**
* This method is called upon plug-in activation
*/
public void start(BundleContext context) throws Exception {
super.start(context);
}
/**
* This method is called when the plug-in is stopped
*/
public void stop(BundleContext context) throws Exception {
super.stop(context);
}
/**
* Returns the shared instance.
*/
public static HelloPlugin getDefault() {
return plugin;
}
/**
* Returns the string from the plugin's resource bundle,
* or 'key' if not found.
*/
public static String getResourceString(String key) {
ResourceBundle bundle = HelloPlugin.getDefault().getResourceBundle();
try {
return (bundle != null) ? bundle.getString(key) : key;
} catch (MissingResourceException e) {
return key;
}
}
/**
* Returns the plugin's resource bundle,
*/
public ResourceBundle getResourceBundle() {
return resourceBundle;
}
}

/****************************串口初始化的package*********************************************/
/*
* Created on 2005-3-3
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.leon.serial;
/**
* @author leon.guo
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
import java.io.*;

/**
*
* This class reads message from the specific serial port and save
* the message to the serial buffer.
*
*/
public class ReadSerial extends Thread
{
private SerialBuffer ComBuffer;
private InputStream ComPort;
/**
*
* Constructor
*
* @param SB The buffer to save the incoming messages.
* @param Port The InputStream from the specific serial port.
*
*/
public ReadSerial(SerialBuffer SB, InputStream Port)
{
ComBuffer = SB;
ComPort = Port;
}
public void run()
{
int c;
try
{
while (true)
{
c = ComPort.read();
ComBuffer.PutChar(c);
}
} catch (IOException e) {}
}
}

/*************************************************************************************************/
/*
* Created on 2005-3-3
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.leon.serial;
/**
* @author leon.guo
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.comm.*;
/**
*
* This bean provides some basic functions to implement full dulplex
* information exchange through the srial port.
*
*/
public class SerialBean
{
static String PortName;
CommPortIdentifier portId;
SerialPort serialPort;
static OutputStream out;
static InputStream in;
SerialBuffer SB;
ReadSerial RT;
/**
*
* Constructor
*
* @param PortID the ID of the serial to be used. 1 for COM1,
* 2 for COM2, etc.
*
*/
public SerialBean(int PortID)
{
PortName = "COM" + PortID;
}

/**
*
* This function initialize the serial port for communication. It startss a
* thread which consistently monitors the serial port. Any signal capturred
* from the serial port is stored into a buffer area.
*
*/
public int Initialize()
{
int InitSuccess = 1;
int InitFail = -1;
try
{
portId = CommPortIdentifier.getPortIdentifier(PortName);
try
{
serialPort = (SerialPort)
portId.open("Serial_Communication", 2000);
} catch (PortInUseException e)
{
return InitFail;
}
//Use InputStream in to read from the serial port, and OutputStream
//out to write to the serial port.
try
{
in = serialPort.getInputStream();
out = serialPort.getOutputStream();
} catch (IOException e)
{
return InitFail;
}
//Initialize the communication parameters to 9600, 8, 1, none.
try
{
serialPort.setSerialPortParams(9600,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
} catch (UnsupportedCommOperationException e)
{
return InitFail;
}
} catch (NoSuchPortException e)
{
return InitFail;
}
// when successfully open the serial port, create a new serial buffer,
// then create a thread that consistently accepts incoming signals from
// the serial port. Incoming signals are stored in the serial buffer.
SB = new SerialBuffer();
RT = new ReadSerial(SB, in);
RT.start();
// return success information
return InitSuccess;
}
/**
*
* This function returns a string with a certain length from the incomin
* messages.
*
* @param Length The length of the string to be returned.
*
*/
public String ReadPort(int Length)
{
String Msg;
Msg = SB.GetMsg(Length);
return Msg;
}
/**
*
* This function sends a message through the serial port.
*
* @param Msg The string to be sent.
*
*/
public void WritePort(String Msg)
{
int c;
try
{
for (int i = 0; i < Msg.length(); i++)
out.write(Msg.charAt(i));
} catch (IOException e) {}
}
/**
*
* This function closes the serial port in use.
*
*/
public void ClosePort()
{
RT.stop();
serialPort.close();
}
}

/*************************************************************************************************/
/*
* Created on 2005-3-3
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.leon.serial;
/**
* @author leon.guo
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
/**
*
* This class implements the buffer area to store incoming data from the serial
* port.
*
*/
public class SerialBuffer
{
private String Content = "";
private String CurrentMsg, TempContent;
private boolean available = false;
private int LengthNeeded = 1;
/**
*
* This function returns a string with a certain length from the incomin
* messages.
*
* @param Length The length of the string to be returned.
*
*/
public synchronized String GetMsg(int Length)
{
LengthNeeded = Length;
notifyAll();

if (LengthNeeded > Content.length())
{
available = false;
while (available == false)
{
try
{
wait();
} catch (InterruptedException e) { }
}
}
CurrentMsg = Content.substring(0, LengthNeeded);
TempContent = Content.substring(LengthNeeded);
Content = TempContent;
LengthNeeded = 1;
notifyAll();
return CurrentMsg;
}
/**
*
* This function stores a character captured from the serial port to the
* buffer area.
*
* @param t The char value of the character to be stored.
*
*/
public synchronized void PutChar(int c)
{
Character d = new Character((char) c);
Content = Content.concat(d.toString());
if (LengthNeeded < Content.length())
{
available = true;
}
notifyAll();
}
}