NullPointerException: name can't be null

[Darren Alexandria]

Good day!
I have this code which I want to implement in an Applet and put in on a JSP page after.

package com.stripmap;
 
import java.applet.Applet;
import java.io.*;
import java.util.*;
 
import javax.comm.CommDriver;
import javax.comm.CommPortIdentifier;
import javax.comm.SerialPort;
import javax.comm.SerialPortEventListener;
import javax.comm.PortInUseException;
import javax.comm.UnsupportedCommOperationException;
import javax.comm.SerialPortEvent;
import com.sun.comm.Win32Driver;
import com.stripmap.Bean;
public class ReadWriteC extends Applet implements Runnable, SerialPortEventListener {

 InputStream   inputStream;
 Thread        readThread;
 String        strReadBytes;

 static CommPortIdentifier portId;
 static Enumeration      portList;
     static OutputStream      outputStream;
 static SerialPort        serialPort;
 static byte[] messageString = {0x52, 0x45, 0x41, 0x44, 0x0D};
 
public void getPorts() throws ClassNotFoundException, InstantiationException, IllegalAccessException{


 portList = CommPortIdentifier.getPortIdentifiers();
 while (portList.hasMoreElements()) { 
            portId = (CommPortIdentifier) portList.nextElement();
            if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
            if (portId.getName().equals("COM1")) {
            try {
                            serialPort = (SerialPort)
                            portId.open("SimpleWriteApp", 2000);
                    } catch (PortInUseException e) {}
                    
                    try {
                        outputStream = serialPort.getOutputStream();
                    } catch (IOException e) {}
                    try {
                        serialPort.setSerialPortParams(9600,
                            SerialPort.DATABITS_8,
                            SerialPort.STOPBITS_1,
                            SerialPort.PARITY_NONE);
                    } catch (UnsupportedCommOperationException e) {}
                    
                                      
                    for(int i = 0; i < messageString.length; i++ ) 
                    {
                        try {                        
                        outputStream.write(messageString[i]);
                        //System.out.print(messageString[i]);
                        } catch (IOException e) {}
                    }// end of for
                    
                    System.out.println("The Strip ID is:  ");
            }//end of if (portId.getName().equals("COM1"))
            }// end of if if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL
 }// end of while (portList.hasMoreElements()
}// end of main
 
public ReadWriteC() {

try {
getPorts();
} catch (ClassNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (InstantiationException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IllegalAccessException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}

 try {
 
            serialPort = (SerialPort) portId.open("SimpleReadApp", 2000);
           
 } catch (PortInUseException e) {
        }
        try {
            inputStream = serialPort.getInputStream();
        } catch (IOException e) {
        System.out.println("Cannot open input stream");
        }
try {
            serialPort.addEventListener(this);
} catch (TooManyListenersException e) {}
        serialPort.notifyOnDataAvailable(true);
        try {
            serialPort.setSerialPortParams(9600,
                SerialPort.DATABITS_8,
                SerialPort.STOPBITS_1,
                SerialPort.PARITY_NONE);
        } catch (UnsupportedCommOperationException e) {}
        readThread = new Thread(this);
        readThread.start();
 }// end of  public ReadWriteC()
 
public void run() {
 try {
            Thread.sleep(20000);
            System.out.println("End of thread.");
        } catch (InterruptedException e) {}
}
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:
            byte[] readBuffer = new byte[60];
 
            try {
                while (inputStream.available() > 0) {
                    int numBytes = inputStream.read(readBuffer);
                }
                strReadBytes = new String(readBuffer);
                System.out.print(strReadBytes); 
            } catch (IOException e) {
            System.out.println("There is no byte to read.");
            }
            break;
        }// end of switch
}// end of public void serialEvent(SerialPortEvent event)

public String getReadBytes() {

return (strReadBytes);
    }// end of getBytes()

}// end of public class ReadWriteC implements Runnable, SerialPortEventListener
 

But after running this program, I get this error:

java.lang.NullPointerException: name can't be null
at java.io.FilePermission.init(Unknown Source)
at java.io.FilePermission.<init>(Unknown Source)
at java.lang.SecurityManager.checkDelete(Unknown Source)
at javax.comm.CommPortIdentifier.getPortIdentifiers(CommPortIdentifier.java:70)
at com.amkor.stripmap.ReadWriteC.getPorts(ReadWriteC.java:38)
at com.amkor.stripmap.ReadWriteC.<init>(ReadWriteC.java:78)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at sun.applet.AppletPanel.createApplet(Unknown Source)
at sun.applet.AppletPanel.runLoader(Unknown Source)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)


What is lacking in my code?

Thanks.

[Ulf Dittmer]

In order to perform socket I/O applets generally need to be signed; is that the case?

As an aside, you should remove the constructor, and move everything that's in it into an init() method.
[ October 19, 2007: Message edited by: Ulf Dittmer ]

[Darren Alexandria]

thank you for your reply!

God bless!