GetClass() and Output Streams

I'm trying to save user preferences to a .Properties file, but I can't seem to correctly find the file when I give a relative path. I had no problem loading the file using:
InputStream inStream = getClass().getResourceAsStream(filename);
try {
load(inStream);
catch (IOException e) {
System.out.println(e);
}The .getResourceAsStream(String) returned an InputStream, so that part was easy. I'm trying to find out if there is something similar to this method that returns an OutputStream or if there is a way to resolve the path to an InputStream to use in the construction of an OutputStream. Thank you for any information you can provide.

getResource() returns a URL...

Similar Messages

Java Input and Output streams

I have maybe simple question, but I can`t really understand how to figure out this problem.
I have 2 applications(one on mobile phone J2ME, one on computer J2SE). They commuinicate with Input and Output Streams. Everything is ok, but all communication is in sequence, for example,
from mobile phone:
out.writeUTF("GETIMAGE")
getImage();
form computer:
reply = in.readUTF();
if(reply.equals("GETIMAGE")) sendimage()
But I need to include one simple thing in my applications - when phone rings there is function in MIDlet - pauseApp() and i need to send some signal to Computer when it happens. But how can i catch this signal in J2SE, because mayble phone rings when computer is sending byte array? and then suddnely it receives command "RINGING"....?
Please explain how to correcly solve such problem?
Thanks,
Ervins

Eh?
TCP/IP is not a multiplexed protocol. And why would you need threads or polling to decipher a record-oriented input stream?
Just send your images in packets with a type byte (1=command, 2=image, &c) and a packet length word. At the receiver:
int type = dataInputStream.read();
int length = dataInputStream.readInt();
byte[] buffer = new byte[length];
int count, read = 0;
while ((count = dataInputStream.read(buffer,count,buffer.length)) > 0)
read += count;
// At this point we either have:
// type == -1 || count = -1 => EOF
// or count > 0, type >= 0, and buffer contains the entire packet.
switch (type)
case -1:
// EOF, not shown
break;
case COMMAND: // assuming a manifest constant somewhere
// process incoming command
break;
case IMAGE:
// process or continue to process incoming image
break;
}No threads, no polling, and nuthin' up my sleeve.
Modulo bugs.

Java Sockets and Output Streams

Hi All,
I am beginning sockets programming and I have a problem. If there is a server listening in the background for incoming connections and say for example 4 client programs programs which we shall call client1...client4 connect. How best can I capture the output streams associated with these newly created sockets so that the server can send back isome nformation to say clients1 and client4 only which is not seen by clients 2 and 3. Similarly I would like the server to send some infor to clients 2 and 3 only which is not seen by client1 and client 4.
Currently I have the server listening part as shown below, but not too sure how to add DISTINCT output streams for 1 and 4 on one hand and 2 and 3 on the other.
Thanks:
// bind socket to a port number
ServerSocket serverSocket = new ServerSocket(portNo);
// create socket to listen to client connection
while (true) {
//listen to an incoming connection
System.out.println("chatroom server waiting for incoming connections");
Socket incomingSocket = serverSocket.accept();
//launch new thread to take care of new connection
chatRoomThread chatThread = new chatRoomThread(incomingSocket);
chatThread.start();
//go back and wait for next connection
Please help.
Thanks,
Bleak

HouseofHunger wrote:
yes thats exactly the way I have my in and out streams, in the run method, but that doesn't help me in filtering traffic, in other words I am saying 2 clients, client1 and client4 for example should share a common in and out stream so that they will see eact other's messages... makes sense.....?No, doesn't make sense. That's the wrong design. Each socket should have its own input and output stream (yes, I know, that's been said several times before). If messages going to client1 should also be sent to client4, then whatever writes the messages to client1's output stream must also write them to client4's output stream. Trying to make those two output streams actually be the same output stream is the wrong way to do that. Just have the controller send the messages to whoever is supposed to get them.

Separate thread for input stream and output stream.

Hi Techies,
In a socket connection, can we run the input stream and output stream in separate threads. actually in my case, the input stream will be getting the input regularly and output stream will send data very rare. so if i impelment them in one class then unless there is data to send output stream will be blocked. i was thinking to impelment both the streams in separate threads. is it a good way? so how to implement it. your guidance will be of great help.
thanks in advance.

JavaBreather wrote:
Hi Techies,
In a socket connection, can we run the input stream and output stream in separate threads.I would say this is the most common way of handling sockets and threads. esp pre-NIO.
Iis it a good way? so how to implement it. your guidance will be of great help.Once you have a socket, create two threads, one which does the reading and one which does the writing.
You could use BlockingQueues to abstract access to these threads. i.e. the reading thread reads something from the socket and adds it to the BlockingQueue. The writing thread take()s something froma second BlockingQueue and writes it to the Socket. This way you add things to write or get thing to process by looking at the BlockingQueues.

Fileinput and output stream

hi. i was trying to learn this fileinput and output stream in java. i was trying to solve this exercise problem in which a user need to ask for the inputfile (Which i have created mydata.txt which has 5 positive numbers and 5 negative numbers ). my program will ask the user for the input file and then output the results in 2 seperate files one output will be for positive integers which the program will extract from myData,txt and negative integers to another output file. i am very confused. my program does not give me any error msgs but outputs a number 0.
import java.util.Scanner;
import java.io.*;
class fileEg {
     public static void main (String[] args) throws IOException
     int num=0, num1;
     Scanner user = new Scanner(System.in);
     String inputFileName, outputFileName, fileName;
     System.out.println("Input File Name ");
     inputFileName = user.nextLine().trim();
     File input = new File (inputFileName);
     Scanner scan = new Scanner(input);
     System.out.print("Output File Name: ");
    outputFileName = user.nextLine().trim();
    File output = new File( outputFileName );
    PrintStream print = new PrintStream( output );
    while(scan.hasNextInt()) {
         if(num == '+') {
              print.println( "the numbers are " + num);
         else {
              print.println("The numbers ares " + num);
         print.close();
}any help will be really appreciated. any theories or example.
Thanks

import java.util.Scanner;
import java.io.*;
class fileEg {
     public static void main (String[] args) throws IOException
     int num;
     Scanner user = new Scanner(System.in);
     String inputFileName, outputFileName, negativeFileName;
     System.out.println("Input File Name ");
     inputFileName = user.nextLine().trim();
     File input = new File (inputFileName);
     Scanner scan = new Scanner(input);
     System.out.print("Output File positive Name: ");
    outputFileName = user.nextLine().trim();
    File output1 = new File( outputFileName );
    PrintStream positiveNumbers = new PrintStream( output1 );
    System.out.print("Output File negative Name: ");
    negativeFileName = user.nextLine().trim();
    File output = new File( negativeFileName );
    PrintStream negativeNumbers = new PrintStream( output );
while(scan.hasNextInt()) {
         num= scan.nextInt();
         if (num >0) {
              positiveNumbers.println( "the numbers are " + num);
         } else {
              negativeNumbers.println("The numbers ares " + num);
positiveNumbers.close();
negativeNumbers.close();
}Thanks paul
Message was edited by:
fastmike

MultiThreading with Input and Output Streams

Hi,
I have a problem and I think it's because I'm not coding correctly. Please help me if you can understand what I'm doing wrong.
I have a server that spawns a separate thread to go off and collect data from a serial port. It also waits to accept connections from any client and if a connection is made it will send that data to the clients connected.
There is data constantly coming in through the serial port. It is output through a DataOutputStream so when the thread is created in the server, I pipe it into a DataInputStream. I do does because I want the server to then read in the data from the inputstream and then send it out to all my clients.
So far, the way I have it set up seems to do this. But my problem occurs when I try to close a client connection. Instead of removing the socket connection it gives me an error that it can't send data to the client, but it shouldn't be sending data to the client because I just closed it. I realize this is probably because I'm still constantly receiving data from my inputstream and the connection was closed so it can't send that data to the client. I know I need to either close the stream or close my socket but I don't know where this needs to be done. I'm stuck on the correct way to fix this.
My second problem is the initial connection made to receive data from the inputstream. This is probably because I'm not very familiar with how input/output streams work. But instead of just sending the client the current data being received in real time, it'll send all the data that's buffered in the inputstream. I don't want all the data that's been collecting to go to that first client. I only want the recent data that is coming through while the client is connected. Does this make sense? Because after I make a second client connection I don't have this problem because the InputStream is no longer buffered up. Should I be using something else besides the DataInputStream?
I feel like I'm going about this the wrong way. Please advise. I'm shy about showing the code but I've included the bulk of it here in hopes that someone will see what I'm doing wrong. The only part that's left out is the thread that reads from the serial port. I don't seem to have any problems with that thread.
Thanks,
kim
===
import java.io.*;
import java.net.*;
import javax.comm.*;
import java.util.*;
// DataServer waits for a client connection
class DataServer
     static final int PORT = 7;
     // The ServerSocket to use for accepting new connections
     private ServerSocket ss;
     // A mapping from sockets to DataOutputStreams. This will
     // help us avoid from having to create a DataOutputStream each time
     // we want to write to a stream.
     private Hashtable outputStreams = new Hashtable();
     // The inputstream that will receive serial port data through a
     // piped inputstream
     public DataInputStream datalogger;
     // Constructor and while-accept loop all in one.
     public DataServer() throws IOException
          try {
               // Creating pipe to convert the outputstream from the
               // RS232 Thread to an inputstream for the server to read
               PipedOutputStream pout = new PipedOutputStream();
               PipedInputStream pin = new PipedInputStream(pout);
               // The inputstream that will receive data from the RS232Thread
               datalogger = new DataInputStream(pin);
               // Spawn the thread that will read data through from
               // the TINI serial port
               new RS232Thread( pout ).start();
               // Begin listening for connections and send data
               listen();
          } catch (IOException ioe) {
               System.out.println("Error >> DataServer::DataServer()");
               System.out.println(ioe.getMessage());
               ioe.printStackTrace();
          } finally {
               try     {
                    System.out.println( "Closing >> DataServer::DataServer()" );
                    datalogger.close();
               } catch (IOException i ) {
                    System.out.println( "Error2 >> DataServer::DataServer()" );
                    System.out.println(i); }
     private void listen() throws IOException
          // Create the ServerSocket
          ss = new ServerSocket( PORT );
          // Inform that the server is ready to go
          System.out.println( "Listening on " + ss );
          // Keep accepting connections forever
          while (true) {
               // Grab the next incoming connection
               Socket s = ss.accept();
               // Inform that connection is made
               System.out.println( "Connection from " + s );
               // Create a DataOutputStream for writing data to the
               // other side
               DataOutputStream dout = new DataOutputStream( s.getOutputStream() );
               // Save this stream so we don't need to make it again
               outputStreams.put( s, dout );
               // Create a new thread for this connection, and then foret
               // about it
               new ServerThread( this, s );
     // Get an enumeration of all the OutputStreams, one for each client
     // connected to the server
     Enumeration getOutputStreams() {
          return outputStreams.elements();
     // Send a message to all clients (utility routine)
     void sendToAll( byte[] b ) {
          // synchronize on this because another thread might be
          // calling removeConnection() and this would screw things up
          // while it walks through the list
          synchronized( outputStreams ) {
               // For each client...
               for (Enumeration e = getOutputStreams(); e.hasMoreElements();) {
                    // ... get the output stream ...
                    DataOutputStream dout = (DataOutputStream)e.nextElement();
                    // ... and send the message
                    try {
                         dout.write( b );
                    } catch(IOException ie) {
                         System.out.println( "Error >> ServerThread::sendToAll()" );
                         System.out.println( ie );
     // remove a socket, and it's corresponding output stream, from the
     // list. This is usually called by a connection thread that has
     // discovered that the connection to the client is dead.
     void removeConnection( Socket s ) {
          // Synchronize so it doesn't mess up sendToAll() while it walks
          // down the list of all output streams
          synchronized( outputStreams ) {
               // Inform about removal
               System.out.println( "Removing connection to " + s );
               // Remove if from our hastable/list
               outputStreams.remove( s );
               // Make sure it's closed
               try {
                    s.close();
               } catch( IOException ie ) {
                    System.out.println( "Error closing " + s );
                    ie.printStackTrace();
     // main - Opens a server socket and spins off a new thread each time
     // a new client connection is accepted on this socket.
     public static void main(String[] args) throws Exception
          System.out.println("Starting DataServer version 1.0 ...");
          try
               new DataServer();
          catch (IOException ioe)
               System.out.println( "Error >> DataServer::main()" );
               System.out.println(ioe.getMessage());
               ioe.printStackTrace();
class ServerThread extends Thread
     //The Server that spawned this thread
     private DataServer server;
     // The Socket connected to the client
     private Socket socket;
     //Constructor
     public ServerThread( DataServer server, Socket socket )
          // save the parameters
          this.server = server;
          this.socket = socket;
          // Start up the thread
          start();
     // This runs in a separate thread when start() is called in the
     // constructor
     public void run() {
          try {
               // The inputstream receiving data from the global inputstream
               // that is piped to the RS232 Thread
               // ???? is this where i'm messing up ???
               DataInputStream in = new DataInputStream( server.datalogger );
               int num = 0;
               byte[] d = new byte[1];
               // read from the inputstream over and over, forever ...
               while( ( num = in.read(d) ) > 0 ) {
                    // ... and have the server send it to all clients
                    server.sendToAll( d );
          } catch (IOException ioe) {
               System.out.println( "Error >> ServerThread::run()" );
               System.out.println(ioe.getMessage());
               ioe.printStackTrace();
          } finally {
               // The connection is closed for one reason or another,
               // so have the server dealing with it
               System.out.println( "Closing" );
               server.removeConnection( socket );

A couple of things to note...
First, you are looping infinitely in your server's constructor. Since the constructor is never completing, your server object is never completely constructed - this may cause indeterminate behaviour when you pass a reference to the server to another thread.
Second, I would recommend fixing your issues by modifying your design somewhat. The design I would recommend (read: The design I would use) is:
A server object, with a public listen method. The constructor spawns a thread to constantly read from the serial port and forward the data read back to the server, via a multicast (sendToAll) method.
The listen method sets up a server socket to accept connections, and in a loop opens client sockets and stores them in a set.
The multicast method iterates through the list of open client sockets, and for each in turn confirms that it is still open. If open, send the data down the socket's output stream; if closed, remove the socket from the set.
Note that this design includes only two threads - the main thread listens for and accepts new socket connections, while the extra thread collects data from the serial port, multicasts it to all of the open sockets, and removes all of the closed sockets. If you require to perform any other communication with the sockets, it may be necessary to create a thread for those sockets, to facilitate reading from their input streams, but in the given design, this is not necessary.
I hope this helps,
-Troy

ObjectInput and Output streams

Hi all,
What is objectInput and Out Stream? For what purpose we r using it?
regards,
Mahe

From the Standard Java API
An ObjectInputStream deserializes primitive data and objects previously written using an ObjectOutputStream.
ObjectOutputStream and ObjectInputStream can provide an application with persistent storage for graphs of objects when used with a FileOutputStream and FileInputStream respectively. ObjectInputStream is used to recover those objects previously serialized. Other uses include passing objects between hosts using a socket stream or for marshaling and unmarshaling arguments and parameters in a remote communication system.
ObjectInputStream ensures that the types of all objects in the graph created from the stream match the classes present in the Java Virtual Machine. Classes are loaded as required using the standard mechanisms.
Only objects that support the java.io.Serializable or java.io.Externalizable interface can be read from streams.
The method readObject is used to read an object from the stream. Java's safe casting should be used to get the desired type. In Java, strings and arrays are objects and are treated as objects during serialization. When read they need to be cast to the expected type.
Primitive data types can be read from the stream using the appropriate method on DataInput.
The default deserialization mechanism for objects restores the contents of each field to the value and type it had when it was written. Fields declared as transient or static are ignored by the deserialization process. References to other objects cause those objects to be read from the stream as necessary. Graphs of objects are restored correctly using a reference sharing mechanism. New objects are always allocated when deserializing, which prevents existing objects from being overwritten.
Reading an object is analogous to running the constructors of a new object. Memory is allocated for the object and initialized to zero (NULL). No-arg constructors are invoked for the non-serializable classes and then the fields of the serializable classes are restored from the stream starting with the serializable class closest to java.lang.object and finishing with the object's most specific class.
For example to read from a stream as written by the example in ObjectOutputStream:
     FileInputStream fis = new FileInputStream("t.tmp");
     ObjectInputStream ois = new ObjectInputStream(fis);
     int i = ois.readInt();
     String today = (String) ois.readObject();
     Date date = (Date) ois.readObject();
     ois.close();
Classes control how they are serialized by implementing either the java.io.Serializable or java.io.Externalizable interfaces.
Implementing the Serializable interface allows object serialization to save and restore the entire state of the object and it allows classes to evolve between the time the stream is written and the time it is read. It automatically traverses references between objects, saving and restoring entire graphs.
Serializable classes that require special handling during the serialization and deserialization process should implement the following methods:
private void writeObject(java.io.ObjectOutputStream stream)
throws IOException;
private void readObject(java.io.ObjectInputStream stream)
throws IOException, ClassNotFoundException;
private void readObjectNoData()
throws ObjectStreamException;
The readObject method is responsible for reading and restoring the state of the object for its particular class using data written to the stream by the corresponding writeObject method. The method does not need to concern itself with the state belonging to its superclasses or subclasses. State is restored by reading data from the ObjectInputStream for the individual fields and making assignments to the appropriate fields of the object. Reading primitive data types is supported by DataInput.
Any attempt to read object data which exceeds the boundaries of the custom data written by the corresponding writeObject method will cause an OptionalDataException to be thrown with an eof field value of true. Non-object reads which exceed the end of the allotted data will reflect the end of data in the same way that they would indicate the end of the stream: bytewise reads will return -1 as the byte read or number of bytes read, and primitive reads will throw EOFExceptions. If there is no corresponding writeObject method, then the end of default serialized data marks the end of the allotted data.
Primitive and object read calls issued from within a readExternal method behave in the same manner--if the stream is already positioned at the end of data written by the corresponding writeExternal method, object reads will throw OptionalDataExceptions with eof set to true, bytewise reads will return -1, and primitive reads will throw EOFExceptions. Note that this behavior does not hold for streams written with the old ObjectStreamConstants.PROTOCOL_VERSION_1 protocol, in which the end of data written by writeExternal methods is not demarcated, and hence cannot be detected.
The readObjectNoData method is responsible for initializing the state of the object for its particular class in the event that the serialization stream does not list the given class as a superclass of the object being deserialized. This may occur in cases where the receiving party uses a different version of the deserialized instance's class than the sending party, and the receiver's version extends classes that are not extended by the sender's version. This may also occur if the serialization stream has been tampered; hence, readObjectNoData is useful for initializing deserialized objects properly despite a "hostile" or incomplete source stream.
Serialization does not read or assign values to the fields of any object that does not implement the java.io.Serializable interface. Subclasses of Objects that are not serializable can be serializable. In this case the non-serializable class must have a no-arg constructor to allow its fields to be initialized. In this case it is the responsibility of the subclass to save and restore the state of the non-serializable class. It is frequently the case that the fields of that class are accessible (public, package, or protected) or that there are get and set methods that can be used to restore the state.
Any exception that occurs while deserializing an object will be caught by the ObjectInputStream and abort the reading process.
Implementing the Externalizable interface allows the object to assume complete control over the contents and format of the object's serialized form. The methods of the Externalizable interface, writeExternal and readExternal, are called to save and restore the objects state. When implemented by a class they can write and read their own state using all of the methods of ObjectOutput and ObjectInput. It is the responsibility of the objects to handle any versioning that occurs.
Edited by: pgeuens on Dec 26, 2007 1:50 PM

Pipes (Input- and Output-streams) to a Process are not closed

Hello experts!
I have a long-living server-process that opens external programs with
Runtime.getRuntime().exec() all the time. For communication with one
of the external program I use stdin and stdout. I close all streams in
finally-blocks, so there should not be any open stream.
The problem is, that most of the time the used streams are closed
correctly. But sometimes some of them left open. I check that with
the linux command-line tool lsof. So over time the number of open
pipes increases and eat up all file-handles till an IOException (too
many open files) is thrown.
If I watch the -verbosegc output, I see that most of the open pipes
are cleaned up after a GC-run. But over time - not all.
I start the external program in a thread, what could explain that
it happens only sometimes.
I'm hunting this bug now for quite a long time. Are there any known
problems with using pipes to/from other processes (under linux?)
thanks
lukas

Hi!
Now I did some heavy logging and I saw that the remaining pipes are the ones I DON'T
open to read or write! No joke! For example - for one process I don't read or write any of
stdin,stdout,stderr - then in one of X executions all three pipes are left open (shown by
lsof for the java-process, after many GC-runs).
To test it I read the stdin of this process - then this stream was closed in the error case,
but stdout and stderr are still open. This is really strange!
anybody seen this before?
lukas

Input and Output Stream conversion

I have problem. In my application I should change OutputStream to InputStream and vv. I try to explain it using easy example.
I am creatin xml document and using XMLOutputter (I am using org.jdom parser) I could write it to file using FileOutputStream, but first I'd like to encrypt this file. For that reason I need InputStream. I write this file on disc, next i read this file, encrypt and write again and at last delete the unencrypted file. Could do It without writeing unencrypted file on disc? Maybe using only streams? Pleas help me, how to do it. Maybe I should convert OutputStream to InputStream.
When I reading information from encrypted file I have the same problem - streams conversion.

I wrote an article about how to convert an OutputStream to an InputStream. You can read the article at:
http://ostermiller.org/convert_java_outputstream_inputstream.html
It discusses three methods for conversion: byte arrays, piped streams, and circular buffers.

Input and output streams

I am struggling with this, if any of you have any advice I would appreciate it.
I am creating a java server that can communicate with a client over tcp sockets and to a device through a serial port. I have have the TCP part all set up. I found this packet and code to be able to communicate through a serial port.
http://rxtx.qbang.org/wiki/index.php/Two_way_communcation_with_the_serial_port
it works by itself, but I don't think I can make it work with my server because I am already using a system.in for the tcp portion of it. In the long run what I want to be able to do is take information from the socket connection, play with it a little bit, and then send it out the serial port to the device.
Is it possible to convert this code to instead of asking for input from the keyboard, to take a string that I can pass in from somewhere, or if something comes in on the serial port to write it to a string or something?

Sorry I was so vague.
this code that i found on the website, creates a connection with the serial port, then it waits for input from the keyboard. once that input comes in, it sends out that stuff through the serial port. I want it to instead of wanting for input from the keyboard, to check to see if there is something in a string or something, if there is write it out to the serial port.
Basically instead of having a listener constantly waiting for input from the keyboard, be able to call a method from the rest of my program to send stuff out the serial port.

Synchronize input and output tasks to start at the same sample point [C++ NI_DAQmx Base]

I'm trying to initiate the analog input and output streams to start reliably at the same sample. I've tried triggering the output from the start of the input using the following code [NI-DAQmx Base 2.1 under Mac OS X with an M-Series multifunction board]. It compiles and runs, but gives an error message at the call to "DAQmxBaseCfgDigEdgeStartTrig". Any suggestions about synchronized I/O on this platform?
#include "NIDAQmxBase.h"
#include
#include
#include
#define DAQmxErrorCheck( functionCall ) { if ( DAQmxFailed( error=( functionCall ) ) ) { goto Error; } }
int main( int argc, char *argv[] )
// Task parameters
int32 error = 0;
TaskHandle inputTaskHandle = 0;
TaskHandle outputTaskHandle = 0;
char errorString[ 2048 ] = {'\0'};
int32 i;
time_t startTime;
// input channel parameters
char inputChannelList[] = "Dev1/ai0, Dev1/ai1";
float64 inputVoltageRangeMinimum = -10.0;
float64 inputVoltageRangeMaximum = 10.0;
// output channel parameters
char outputChannelList[] = "Dev1/ao0, Dev1/ao1";
char outputTrigger[] = "Dev1/ai/StartTrigger";
float64 outputVoltageRangeMinimum = -10.0;
float64 outputVoltageRangeMaximum = 10.0;
// Timing parameters
char clockSource[] = "OnboardClock";
uInt64 samplesPerChannel = 100000;
float64 sampleRate = 10000.0;
// Input data parameters
static const uInt32 inputBufferSize = 100;
int16 inputData[ inputBufferSize * 2 ];
int32 pointsToRead = inputBufferSize;
int32 pointsRead;
float64 timeout = 10.0;
int32 totalRead = 0;
// Output data parameters
static const uInt32 outputBufferSize = 1000;
float64 outputData[ outputBufferSize * 2 ];
int32 pointsToWrite = outputBufferSize;
int32 pointsWritten;
for( int i = 0; i < outputBufferSize; i++ )
outputData[ 2 * i ] = 9.95 * sin( 2.0 * 3.14159 * i / outputBufferSize );
outputData[ 2 * i + 1 ] = -9.95 * sin( 2.0 * 3.14159 * i / outputBufferSize );
// ------------------- configure input task -----------------------
DAQmxErrorCheck ( DAQmxBaseCreateTask( "", &inputTaskHandle ) );
printf( "Created input task\n" );
DAQmxErrorCheck ( DAQmxBaseCreateAIVoltageChan( inputTaskHandle, inputChannelList, "", DAQmx_Val_RSE, inputVoltageRangeMinimum, inputVoltageRangeMaximum, DAQmx_Val_Volts, NULL ) );
printf( "Created AI Voltage Chan\n" );
DAQmxErrorCheck ( DAQmxBaseCfgSampClkTiming( inputTaskHandle, clockSource, sampleRate, DAQmx_Val_Rising, DAQmx_Val_ContSamps, samplesPerChannel ) );
printf( "Set sample rate\n" );
// ------------------- configure output task -----------------------
DAQmxErrorCheck ( DAQmxBaseCreateTask( "", &outputTaskHandle ) );
printf( "Created output task\n" );
DAQmxErrorCheck ( DAQmxBaseCreateAOVoltageChan( outputTaskHandle, outputChannelList, "", outputVoltageRangeMinimum, outputVoltageRangeMaximum, DAQmx_Val_Volts, NULL ) );
printf( "Created AO Voltage Chan OK\n" );
DAQmxErrorCheck ( DAQmxBaseCfgSampClkTiming( outputTaskHandle, clockSource, sampleRate, DAQmx_Val_Rising, DAQmx_Val_ContSamps, samplesPerChannel ) );
printf( "Set sample rate\n" );
// trigger output when input starts
DAQmxErrorCheck ( DAQmxBaseCfgDigEdgeStartTrig( outputTaskHandle, outputTrigger, DAQmx_Val_Rising ) );
printf( "Set output trigger\n" );
// ------------------- configuration -----------------------
// write output signal
DAQmxErrorCheck ( DAQmxBaseWriteAnalogF64( outputTaskHandle, pointsToWrite, 0, timeout, DAQmx_Val_GroupByScanNumber, outputData, &pointsWritten, NULL ) );
printf( "Write output signal\n" );
// set up input buffer
DAQmxErrorCheck ( DAQmxBaseCfgInputBuffer( inputTaskHandle, 200000 ) ); // use a 100,000 sample DMA buffer
// initiate acquisition - must start output task first
DAQmxErrorCheck ( DAQmxBaseStartTask( outputTaskHandle ) );
DAQmxErrorCheck ( DAQmxBaseStartTask( inputTaskHandle ) );
// The loop will quit after 10 seconds
Dr John Clements
Lead Programmer
AxoGraph Scientific

Hi Michael,
First of all, thanks very much for taking the time to investigate this problem! Much appreciated.
You asked for "an actual error code you got and any description that is given". The full output from the program that I posted earlier in this thread is appended to the end of this message. In summary, following the call to...
DAQmxErrorCheck ( DAQmxBaseCfgDigEdgeStartTrig( outputTaskHandle, outputTrigger, DAQmx_Val_Rising ) );
... with ...
char outputTrigger[] = "Dev1/ai/StartTrigger";
...the error message is ...
DAQmxBase Error: Specified route cannot be satisfied, because the hardware does not support it.
You asked "specifically which M series device you are using"? It is the PCIe 6251 (with BNC 2111 connector block). I'm testing and developing on an Intel Mac Pro (dual boot OS X and Windows XP).
You asked for "the location you pulled the code from". Here it is...
http://zone.ni.com/devzone/cda/epd/p/id/879
...specifically from the file "Multi-Function-Synch AI-AO_Fn.c".
I adapted the NI-DAQmx calls to their NI-DAQmx Base equivalents.
Finally, you asked "Is the trigger necessary, or do you just need to know that the measurements are running on the same clock?". I believe that some kind of sychronized trigger is necessary in my situation (correct me if I'm wrong). Timing is crucial. Say I initiate an analog output stream that delivers a voltage command step 5 ms from the onset. I need to record the response (analog input stream) so that its onset is accurately aligned (synchronized) at 5 ms. A typical recording situation would stimulate and record a short data 'sweep', then wait for the (biological) system to recover, then stimulate and record another short sweep, and repeat. I need all the recorded sweeps to align accurately so that they can be averaged and analyzed conveniently.
I definitely do not want my customers to rely on an expensive external TTL pulse generator to initiate and synchronize each 'sweep'. That would effectively eliminate the cost advantage of an NI board, as well as adding unnecessary complexity in setup and use. It would be a show-stopper for me.
It seems perverse, but would it be possible to use a digital output channel connected directly to a digital input chanel to trigger the input and output streams?
Regards,
John.
Full output from test program. Compiled with gcc 4 under OS X...
[Session started at 2007-05-23 14:17:01 +1000.]
LoadRuntime: MainBundle
CFBundle 0x303cc0 (executable, loaded)
_CompatibleWithLabVIEWVersion: linkedAgainst: 08208002
_CompatibleWithLabVIEWVersion: result= false, mgErr= 1, theActualVersion= 00000000
_CompatibleWithLabVIEWVersion: linkedAgainst: deadbeef
_CompatibleWithLabVIEWVersion: Reseting Linked Against
_CompatibleWithLabVIEWVersion: linkedAgainst: 08208002
_CompatibleWithLabVIEWVersion: result= true, mgErr= 0, theActualVersion= 00000000
_CompatibleWithLabVIEWVersion: linkedAgainst: 08208002
_CompatibleWithLabVIEWVersion: result= true, mgErr= 0, theActualVersion= 00000000
com.ni.LabVIEW.dll.nidaqmxbaselv
CFBundle 0x313760 (framework, loaded)
{type = 15, string = file://localhost/Library/Frameworks/nidaqmxbaselv.framework/, base = (null)}
Amethyst:Library:Frameworks:nidaqmxbaselv.framework
2007-05-23 14:17:02.248 test-ni[4445] CFLog (21): Error loading /Library/Frameworks/LabVIEW 8.2 Runtime.framework/resource/nitaglv.framework/nitaglv: error code 4, error number 0 (no suitable image found. Did find:
/Library/Frameworks/LabVIEW 8.2 Runtime.framework/resource/nitaglv.framework/nitaglv: mach-o, but wrong architecture)
CFBundle 0x1751fdc0 (framework, not loaded)
Created input task
Created AI Voltage Chan
Set sample rate
Created output task
Created AO Voltage Chan OK
Set sample rate
DAQmxBase Error: Specified route cannot be satisfied, because the hardware does not support it.
test-ni has exited with status 0.
Dr John Clements
Lead Programmer
AxoGraph Scientific

Sending Data Through a Output Stream...

Hello,
I am writing a program that works on a network...a server is running and client will connect to the server and send specific data for the server to complete transactions on.
The transactions that are mainly seen are SQL SELECT statements and as you can imagine a statement could bring back many records.
At present I have been able to send specific data through streams and have turned this into parameters on the server side and performed SQL. What I need help with or suggestions on is how to get the data back to the client. In some cases it may need to be displayed on screen or just used for further processing?
Please let me know if this is not 100% clear.
Thanks,
P

If you are able to send data over a network, then I assume that you know how to do network programming in Java, as well as knowing SQL.
Java has JDBC - Java DataBase Connectivity API that supports your requirements in full.
If you require a custom solution, then you need to be able to read data back from the server - when the server returns the ResultSet back to the client.
A Socket object has both input and output streams. Seems that you know about the output stream, do you not know about the input stream?
If the server is setup to send data back to the client over the same socket, then you should simply be able to read the results back from the socket's input stream.

Runtime.exec() output streams

Hi,
I am using Runtime.exec() to execute a whole slew of commands - running batch files and executables. It is really important that I can see the output of my programs, and the fact that Runtime.exec() doesn't spawn its own Command-Prompts is a little disconcerting. In order to get around this, I am handling the stdout and stderr output streams from the processes synchronously with threads (as detailed in the Java Pitfall article - http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html). I call Runtime.exec(command[], env[], dir) where command contains "cmd.exe" "\C" command.
My question is, if one of my processes crashes, will my threads receive ALL of the output from stdout and stderr just as a Command-Prompt would? If not, what is the workaround? Using Psexec to run the processes seems to bring up the Command-Prompts like I would like it to, but that doesn't always behave the way it should be, so I cannot rely on that just to see the command prompts.
I don't want to have to switch to C# or C++ to do this at this point, but if there's no real answer, it looks like I might have to.

cotton.m wrote:
munky135 wrote:
Hi,
I am using Runtime.exec() to execute a whole slew of commands - running batch files and executables. It is really important that I can see the output of my programs, and the fact that Runtime.exec() doesn't spawn its own Command-Prompts is a little disconcerting.Hilarious. Oh. You were being serious there were you? :|Yes, I was being serious. I call runtime exec and I am not getting Command-Prompts to pop up, their output is being piped to my Java application. Reading directly from the API:
The Runtime.exec methods may not work well for special processes on certain native platforms, such as native windowing processes, daemon processes, Win16/DOS processes on Microsoft Windows, or shell scripts. The created subprocess does not have its own terminal or console. All its standard io (i.e. stdin, stdout, stderr) operations will be redirected to the parent process through three streams (Process.getOutputStream(), Process.getInputStream(), Process.getErrorStream()). The parent process uses these streams to feed input to and get output from the subprocess. Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, and even deadlock.
>
I don't want to have to switch to C# or C++ to do this at this point, but if there's no real answer, it looks like I might have to.Based on your attitude you should switch. You obviously hate Java and are ready to see faults that don't exist based on misconceptions that you hold. Fine, to each their own. Choose a language you like then. Which at a guess I would say is likely VB.Huh? I love Java. Any misconceptions I hold are from this guys article here - http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html

Read Zip File and output it to the Stream

Hi,
I really need help with this topic. I need to write a function which as input read the zip file (inside: jpeg, mp3, xml)
and as output provide the output Stream of this zip file.
public OutputStream readZipToStream(String sourceZipFile) { ....}
I've tried something....
public static OutputStream    readZipToStream(String src, HttpServletResponse response) throws Exception {
        File fsrc = null;
        ZipOutputStream out = null;
        byte buffer [] = null;
        FileInputStream in = null;
        try {
            buffer = new byte[BUFFER_CREATE];
            fsrc = new File(src);
            out = new ZipOutputStream(response.getOutputStream());
            ZipEntry zipAdd = new ZipEntry(fsrc.getName());
            zipAdd.setTime(fsrc.lastModified());
            out.putNextEntry(zipAdd);
            // Read input & write to output
            in = new FileInputStream(fsrc);
            while (true) {
                int nRead = in.read(buffer, 0, buffer.length);
                if (nRead <= 0)
                    break;
                out.write(buffer, 0, nRead);
            out.flush();
            in.close();
        } catch (IOException ioe) {
            logger.error("Zip Exception: " + ioe.getMessage());
            ioe.printStackTrace();
            throw ioe;
        return out;
    } But the problem with this code when it returns ( I called from servlet: bellow)
it ask user to save the file as servlet.jsp file. So I would have to rename it to zip file later.
What I want to achive is it would ask to save zip file from the stream as name of the original zip file (if that is possible)
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%
OutputStream stream = null;
response.setContentType("application/zip");
target = mount_media + File.separator + "test_swf.zip";
try {
stream = ZipUtil.readZipToStream(target, response);
} catch (Exception ex) {
        System.out.println(ex.getMessage());
    } finally {
if(stream != null) {
            stream.close();
%>
<%@page import="java.io.File" %>
<%@page import="java.io.OutputStream" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
</body>
</html>

Hi oleg_s ,
There's a contradiction of content in your JSP :
response.setContentType("application/zip");
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">The html part of your JSP seems useless for what you mean to do. Therefore, instead of a JSP, you should use a simple servlet to send your zip file.

Servlet Output Streams and clearing

I am using servlets, and I want to be able to print something repeatedly. Well, that's not exactly true: I can print something repeatedly. Using a ServletOutputStream, it doesn't seem possible to clear what has already been written. Here's the code:
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.io.*;
public class AlwaysTime extends HttpServlet {
     public void doPost(HttpServletRequest req, HttpServletResponse res)                throws ServletException, IOException {
          HttpServletResponse oldRes = res;
          Date now = new Date();
          res.setContentType("text/html");
          ServletOutputStream out = res.getOutputStream();
          out.println("<html>");
          out.println("<head>");
          out.println("<title>Clock</title>");
          out.println("</head>");
          out.println("<body>");
          out.println("<h1 align=\"Center\">");
          out.println(now.toString());
          out.println("</h1>");
          out.println("</body>");
          out.println("</html>");
          try {
             Thread.sleep(1000);
          } catch (InterruptedException ie) {}
          // Do nothing: wait for 1 second.
          doPost(req, oldRes);
     public void doGet(HttpServletRequest req, HttpServletResponse res)
          throws ServletException, IOException {
          doPost(req, res);
}This code prints the time every second, but I want to clear the previous output stream. I thought the code shown above would work, but of course, oldRes points to the same object as res. But I don't know how to clear an output stream, so that it is completely empty. Instead, each of the new lines are appended to the same output stream.
This doesn't only apply to servlet output streams: is there some way to clear the System output stream, for instance?
But mainly the servlet output stream ...

You would not want to use HTTP for this type of functionality. HTTP is known as a 'stateless' protocol that simply returns one exact response for each request. So, there is not way to 'clear' the stream (technically, you would not do so for 'normal' streams either, but when you add HTTP into the mix, the task is definitely not possible).
You could implement the above using a RSS feed, or by using HTTP meta-refresh tags on the page itself ot resubmit the requests every second (though this would be inefficient). An applet would also do the task.
- Saish

GetClass() and Output Streams

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