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ProcTool.java

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package net.threebit.utils.sosc;

/*
        Copyright 2003 Shawn Deleurme
        Copyright 2003 Kevin O'Donnell

        This program is free software; you can redistribute it and/or modify
        it under the terms of the GNU General Public License as published by
        the Free Software Foundation; either version 2 of the License, or
        (at your option) any later version.

        This program is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with this program; if not, write to the Free Software
        Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

import com.oreilly.servlet.*;
import java.io.*;
import java.sql.*;
import java.util.*;

public class ProcTool {

        String[] cmd = null;
        Process process = null;
        BufferedReader stdout = null;
        BufferedReader stderr = null;
        PrintWriter stdin = null;
        StringBuffer sbout = new StringBuffer();
        StringBuffer sberr = new StringBuffer();
        ReaderToBuffer bo = null;
        ReaderToBuffer be = null;

        public ProcTool (String[] cmd) throws Exception {
                this.cmd = cmd;
                start();
        }

        public String getOutput() throws Exception {
                if (bo == null) { return null; }
                return bo.getBuffer();
        }

        public String getError() throws Exception {
                if (be == null) { return null; }
                return be.getBuffer();
        }

        public OutputStream getStdin() throws Exception {
                return process.getOutputStream();
        }

        public synchronized void waitFor() throws Exception {
                if (process == null) { throw new Exception("Cannot wait for the process: It has not been started."); }

                // BEGING BLOCK OF THINGS TO TRY AND NOT DEADLOCK THE SYSTEM
                stdout = null;
                stderr = null;
                stdin = null;
                bo = null;
                be = null;
                try { process.getInputStream().close(); } catch (Exception e) { }; // TODO: log
                try { process.getErrorStream().close(); } catch (Exception e) { }; // TODO: log
                try { process.getOutputStream().close(); } catch (Exception e) { }; // TODO: log
                // END
                System.gc();
                process.waitFor();
        }

        private synchronized void start() throws Exception {

                if (process != null) { throw new Exception("Cannot start(): Process has already been started."); }
                process = Runtime.getRuntime().exec(cmd);

                // Connect the processes stdin/stdout/stderr streams to higher level objects.
                stdout = new BufferedReader( new InputStreamReader( process.getInputStream() ));
                stderr = new BufferedReader( new InputStreamReader( process.getErrorStream() ));
                stdin = new PrintWriter( process.getOutputStream() );

                // Start 2 threads to continually read from the processes "output" steamds; 
                bo = new ReaderToBuffer(stdout);
                be = new ReaderToBuffer(stderr);
                bo.start();
                be.start();

        }

        class ReaderToBuffer extends Thread {
                BufferedReader br;
                StringBuffer sb = new StringBuffer();
                public ReaderToBuffer (BufferedReader br) {
                        this.br = br;
                }
                public void run() {
                        try {
                                String line;
                                while ((line = br.readLine()) != null) {
                                        synchronized (sb) { sb.append(line); sb.append("\n"); }
                                        // System.out.println("ReaderToBuffer.run(): " + line);
                                }
                        }
                        catch (Exception e) {
                                // TODO: handle exceptions
                        }
                }
                public String getBuffer() {
                        synchronized (sb) {
                                String result = sb.toString();
                                if (sb.length() > 0) { sb.delete(0, sb.length()-1); }
                                return result;
                        }
                }
        }

}

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