com.crushpaper.ThreadedSynchronousStreamReader.java Source code

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Here is the source code for com.crushpaper.ThreadedSynchronousStreamReader.java

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/*
Copyright 2015 CrushPaper.com.
    
This file is part of CrushPaper.
    
CrushPaper is free software: you can redistribute it and/or modify
it under the terms of version 3 of the GNU Affero General Public
License as published by the Free Software Foundation.
    
CrushPaper 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 Affero General Public License for more details.
    
You should have received a copy of the GNU Affero General Public License
along with CrushPaper.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.crushpaper;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.commons.lang3.ArrayUtils;

/** See the javadoc for `exec()` static member function of this class. */
public class ThreadedSynchronousStreamReader {

    /** A helper class that reads input into a string buffer in its own thread. */
    private static class ReaderThread extends Thread {
        InputStream inputStream;
        StringBuffer result;

        private ReaderThread(InputStream inputStream, StringBuffer result) {
            this.inputStream = inputStream;
            this.result = result;
        }

        @Override
        public void run() {
            try {
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                String line = null;
                while ((line = bufferedReader.readLine()) != null)
                    result.append(line);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    /**
     * Synchronously forks a child process capturing its standard out and err
     * into StringBuffers. Returns the child process's exit code or -1 if it is
     * not available. It creates threads for each stream because that is
     * required in Java to avoid the possibility of deadlock.
     */
    public static int exec(StringBuffer output, StringBuffer error, String args[]) {
        try {
            String osName = System.getProperty("os.name");
            if (osName.equals("Windows 95")) {
                String[] prefix = new String[2];
                prefix[0] = "command.com";
                prefix[1] = "/C";
                args = ArrayUtils.addAll(prefix, args);
            } else if (osName.startsWith("Windows")) {
                String[] prefix = new String[2];
                prefix[0] = "cmd.exe";
                prefix[1] = "/C";
                args = ArrayUtils.addAll(prefix, args);
            }

            Runtime runtime = Runtime.getRuntime();
            Process childProcess = runtime.exec(args);
            ReaderThread errorReader = new ReaderThread(childProcess.getErrorStream(), output);
            ReaderThread outputReader = new ReaderThread(childProcess.getInputStream(), error);
            errorReader.start();
            outputReader.start();
            int exitValue = childProcess.waitFor();
            return exitValue;
        } catch (Throwable t) {
            t.printStackTrace();
        }

        return -1;
    }
}