Thread: Sending SMS in java

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You have provided quite a bit of code with a line that doesn't line up to anything, can you explicitly highlight or write which line of code the exception is thrown on?

Below codes are the one that it couldn't run and occur the error "java.lang.NullPointerException at SMSGateway$SMSQueueThread.run(SMSGateway.java:350) ".

Guide me.Thank you.

 
       while(true)
            {
                Socket connectToClient = ss.accept();
                    HandleAClient thread = new HandleAClient(connectToClient);
                thread.start();
            }
        }
        catch(IOException ex)
        {
            System.err.println(ex);
        }
    }
 
    public void receiveSms(int statusCode, String errmsg, SmsMsgIncoming msg)
 
    {
 
        if(statusCode == SmsTerminal.SC_OK)
            {
            System.out.println(res.getString("samplesmsapp.msg_received:_") + msg.toString());
 
 
            // Recieved SMS & HP
            String rAdm = msg.getMessage();
            String rNum = msg.getSenderNumber();
 
            System.out.println("Recieve Message : " + rAdm);
            System.out.println("Recieve Number : " + rNum);
 
            // INSERT SMS & HP INTO DATABASE
            try {
 
                String xxx;
                xxx="";
                System.out.println("+65 ooo : " + xxx);
                stmt = con.createStatement();
                stmt.executeUpdate("INSERT INTO records(sms_id,admission_no,mobile_no,status,datetime) VALUES(null,'"+rAdm+"','"+rNum.substring(3, rNum.length())+"','in', now())");
 
 
            }
            catch (Exception e)
            {
                System.out.println("Exception in mySQL(): " + e.getMessage() );
            }
        }
        else
        {
            System.err.println(res.getString("samplesmsapp.error_receiving_SMS_message:_") + errmsg);
        }
    }
 
    public void destroy()
    {
        try {
            if (con != null)
                con.close();
        }
        catch (SQLException excIgnored){}
    }   // End destroy()
 
 
    class HandleAClient extends Thread
    {
        private Socket connectToClient;
 
        public HandleAClient(Socket socket)
        {
            this.connectToClient = socket;
        }
 
        public void run()
        {
 
            synchronized(connectToClient)
            {
                try
                    {
                    BufferedReader fromClient = new BufferedReader(new InputStreamReader(connectToClient.getInputStream()));
                    PrintWriter toClient = new PrintWriter(connectToClient.getOutputStream(), true);
 
                    String selection, outputLine;
                    while ((selection = fromClient.readLine()) != null)
                    {
                        String msg = "";
                        String num = "";
 
                        if(selection.equals("phone"))
                        {
                            // RECIEVE NUMBERS AND MSG FROM SERVLET
                            num = fromClient.readLine();
                            msg = fromClient.readLine();
 
                            System.out.println("Phone = " + num);
                            System.out.println("Message = " + msg);
 
                            try {
                                smsQueue.offer(new OutMessage(num, msg),10,TimeUnit.SECONDS);
                            }
                            catch (InterruptedException ie)
                            {
                                ie.printStackTrace();
                            }
 
                        //  SendSMS sms = new SendSMS(num, msg);
                        //  sms.start();
                        }
                        else
                        {
                            // RECIEVE GROUP AND MSG FROM SERVLET
                            String group = fromClient.readLine();
                            msg = fromClient.readLine();
 
                            System.out.println("Group : "+group);
 
                            try
                            {
                                stmt = con.createStatement();
                                rs = stmt.executeQuery("SELECT mobile_no FROM student WHERE course = '"+group+"'");
 
                                while(rs.next())
                                {
                                    num = num + rs.getString(1) + ",";
                                }
 
                                System.out.println("Numbers = " + num);
 
                                smsQueue.offer(new OutMessage(num, msg),10,TimeUnit.SECONDS);
 
                            //  SendSMS sms = new SendSMS(num, msg);
                            //  sms.start();
                            }
                            catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
                catch(IOException ex)
                {
                    System.err.println(ex);
                }
            }
        }
    }
 
    class SendSMS extends Thread
    {
        private String num;
        private String msg;
 
        public SendSMS(String numbers, String message)
        {
            num = numbers;
            msg = message;
            System.out.println("Message = " + message);
        }
 
        public void run()
        {
            // BREAKING NUMBERS INTO TOKENS
            StringTokenizer st = new StringTokenizer(num,",");
 
            while (st.hasMoreTokens())
            {
 
                String sendNum_65 =st.nextToken().trim();
                String sendNum = "65" + sendNum_65;
                System.out.println("Phone = " + sendNum);
 
                // SEND INDIVIDUAL TOKENS
                try
                {
                    System.err.println(res.getString("samplesmsapp.msg:_'") + sendNum + "', '" + msg + "'");
                    term.sendMessage(sendNum, msg);
 
                    try
                    {
                        stmt = con.createStatement();
                        stmt.executeUpdate("INSERT INTO smsrecords(admission_no,mobile_no,status,datetime)  VALUES('"+sendNum_65+"','"+msg+"', now(), 'out')");
 
                                        }
                    catch (Exception e)
                    {
                        System.out.println("Exception in mySQL(): " + e.getMessage() );
                    }
                    Thread.sleep(4800);
                }
                catch (StringIndexOutOfBoundsException e)
                {
                    System.err.println(res.getString("samplesmsapp.msg_format:_number:message"));
                }
                catch(Exception ex) { }
            }
        }
    }
 
            public class SMSQueueThread extends Thread
    {
        private SynchronousQueue smsQueue;
        private String consumerName;
        private PrintStream printStream;
        public SMSQueueThread(String consumerName, SynchronousQueue smsQueue, PrintStream printStream)
        {
            this.consumerName = consumerName;
            this.smsQueue = smsQueue;
            this.printStream = printStream;
        }
 
        public void run()
        {
            while (true)
            {
              try
              {
 
                OutMessage poll = (OutMessage)smsQueue.poll(20,TimeUnit.SECONDS);
                printStream.println(this.consumerName + ": " + poll.getMsg() + " " + poll.gethpnumbers());
 
                // BREAKING NUMBERS INTO TOKENS
                StringTokenizer st = new StringTokenizer(poll.gethpnumbers(),",");
 
                while (st.hasMoreTokens())
                {
                    String sendNum_65 =st.nextToken().trim();
                    String sendNum = "65" + sendNum_65;
                    System.out.println("Phone = " + sendNum);
 
                    // SEND INDIVIDUAL TOKENS
                    try
                    {
                        System.err.println(res.getString("samplesmsapp.msg:_'") + sendNum + "', '" + poll.getMsg() + "'");
                        term.sendMessage(sendNum, poll.getMsg());
 
                        try
                        {
                            stmt = con.createStatement();
                            stmt.executeUpdate("INSERT INTO records(admission_no,mobile_no,status,datetime)  VALUES('"+sendNum_65+"','"+poll.getMsg()+"', now(), 'out')");
                                }
                        catch (Exception e)
                        {
                            System.out.println("Exception in mySQL(): " + e.getMessage() );
                        }
                        Thread.sleep(4800);
                    }
                    catch (StringIndexOutOfBoundsException e)
                    {
                        System.err.println(res.getString("samplesmsapp.msg_format:_number:message"));
                    }
                    catch(Exception ex) {
                        ex.printStackTrace();
                    }
                }
              }
              catch (InterruptedException ie)
              {
                ie.printStackTrace();
              }
              catch (NullPointerException ne)
              {
                ne.printStackTrace();
              }
            }
        }
    }
}

That still doesn't help. The exception has a line number in it (350), which doesn't seem to match up to anything in your code...it is important to tell us where that is. In more general terms, should you want more expedient help you have to help those trying to answer your question with all the info available, which includes the EXACT location the exception is thrown on (given the length of code, I and probably others don't have the time to try and run the code let alone inspect every variable, line, and loop for a Null reference).

Line 350

  OutMessage poll = (OutMessage)smsQueue.poll(20,TimeUnit.SECONDS);

Read the API for SynchronousQueue.poll, null is returned if no element is available. Suggest you first check the size of the queue first before trying to remove and cast something that isn't there.

Thank you for the above error.But it encounter the same java.lang.NullPointerExcerption in the next line which is line 351.

  printStream.println(this.consumerName + ": " + poll.getMsg() + " " + poll.gethpnumbers());

Are you sure what the status of the variables on that line are? Try debugging by adding some println statements in there to make sure your variables are not null. For example

if ( poll == null ){
    System.out.println("Poll is null");
}

Doing so allows you to run through your code several times and backtrack through the variables to see if/where a variable is set to some value (in this case null) - an important technique to learn in debugging, stripping apart code and figuring out its status at a given time to see where the errors are.

Pardon me..but I still got the same error even thou I took your advice.=(

Originally Posted by pipi

Pardon me..but I still got the same error even thou I took your advice.=(

You will still get an error if you follow my advice from my previous post. What did it print out? The point of my previous post was for you to determine what is null using println's, then backtrack through the code using using a similar technique to determine the source of the null reference. If a NullPointerException is thrown, something is null. Add some println's to determine what is, then figure out why it is null.

I am still confuse.
Anyway did I place the code correctly

 
	public void run()
		{
			while (true)
			{
			  try
			  {
			  	//Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time, for another thread to insert it.
			  	//timeout - how long to wait before giving up, in units of unit,unit - a TimeUnit determining how to interpret the timeout parameter
			    OutMessage poll = (OutMessage)smsQueue.poll(30,TimeUnit.SECONDS);
			   printStream.println(this.consumerName + ": " + poll.getMsg() + " " + poll.gethpnumbers());
			   if ( poll == null ){
               System.out.println("Poll is null");
                  }

That println statement is for your benefit, not the code. It lets you see the values of variables through the runtime of a program. I doubt it prints anything as you try to access poll as an object and if it is null the Exception will be thrown before that statement is reached.

Sorry but I'm kinda of lost.What should I do?