Streaming with commons-exec?

Question

Can someone give me an example of how to pass the result of an external program executed using DefaultExecutor ? I do not find documentation describing how to do this.

My external process will work for several hours, so just grabbing all the output is impossible; It must be streaming.

Answer 1

Note: this solution is synchronous, so it will not be transmitted. You will need to read in a separate stream or use the asynchronous version of the execute command.

 private InputStream getStream() { String dataParsingCommand = "java"; PipedOutputStream output = new PipedOutputStream(); PumpStreamHandler psh = new PumpStreamHandler(output); CommandLine cl = CommandLine.parse(command); cl.addArgument("-jar"); cl.addArgument(dataParserPath); DefaultExecutor exec = new DefaultExecutor(); DataInputStream is = null; try { is = new DataInputStream(new PipedInputStream(output)); exec.setStreamHandler(psh); exec.execute(dataParserCommandLine); } catch (ExecuteException ex) { } catch (IOException ex) { } return is; } 

Answer 2

The following is sample code for using Runtime.exec. It would be easy to adapt it to your use. From http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html?page=4

 import java.util.*; import java.io.*; class StreamGobbler extends Thread { InputStream is; String type; StreamGobbler(InputStream is, String type) { this.is = is; this.type = type; } public void run() { try { InputStreamReader isr = new InputStreamReader(is); BufferedReader br = new BufferedReader(isr); String line=null; while ( (line = br.readLine()) != null) System.out.println(type + ">" + line); } catch (IOException ioe) { ioe.printStackTrace(); } } } public class GoodWindowsExec { public static void main(String args[]) { if (args.length < 1) { System.out.println("USAGE: java GoodWindowsExec <cmd>"); System.exit(1); } try { String osName = System.getProperty("os.name" ); String[] cmd = new String[3]; if( osName.equals( "Windows NT" ) ) { cmd[0] = "cmd.exe" ; cmd[1] = "/C" ; cmd[2] = args[0]; } else if( osName.equals( "Windows 95" ) ) { cmd[0] = "command.com" ; cmd[1] = "/C" ; cmd[2] = args[0]; } Runtime rt = Runtime.getRuntime(); System.out.println("Execing " + cmd[0] + " " + cmd[1] + " " + cmd[2]); Process proc = rt.exec(cmd); // any error message? StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), "ERROR"); // any output? StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT"); // kick them off errorGobbler.start(); outputGobbler.start(); // any error??? int exitVal = proc.waitFor(); System.out.println("ExitValue: " + exitVal); } catch (Throwable t) { t.printStackTrace(); } } } 

EDIT: This does not exactly answer the question, since it uses JDK classes, but it works.