de.pawlidi.openaletheia.utils.exec.ProcessExecutor.java Source code

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Here is the source code for de.pawlidi.openaletheia.utils.exec.ProcessExecutor.java

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/*
 * Copyright (C) 2016 Maximilian Pawlidi
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.pawlidi.openaletheia.utils.exec;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.commons.exec.CommandLine;
import org.apache.commons.exec.DefaultExecutor;
import org.apache.commons.exec.ExecuteWatchdog;
import org.apache.commons.exec.Executor;
import org.apache.commons.exec.PumpStreamHandler;
import org.apache.commons.lang.ArrayUtils;
import org.apache.commons.lang.StringUtils;

/**
 * This class provides methods to execute shell commands from jvm.
 * 
 * @author PAWLIDIM
 *
 */
public final class ProcessExecutor {

    /** Process watchdog timeout definition */
    public static final long WATCHDOG_TIMEOUT = 60000;

    /** Process output level definition */
    public static final int PROCESS_OUTPUT_LEVEL = 1;

    /** Invisible default constructor. */
    private ProcessExecutor() {
        super();
    }

    /**
     * Execute given system command without arguments.
     * 
     * @param command
     *            to execute
     * @return command output as String, null otherwise
     */
    public static String executeCommand(final String command) {
        return executeCommand(command, new String[] {});
    }

    /**
     * Execute given system command with arguments.
     * 
     * @param command
     *            to execute
     * @param args
     *            as command arguments
     * @return command output as String, null otherwise
     */
    public static String executeCommand(final String command, String... args) {
        if (StringUtils.isNotEmpty(command)) {

            // create string output for executor
            ProcessStringOutput processOutput = new ProcessStringOutput(PROCESS_OUTPUT_LEVEL);
            // create external process
            Executor executor = createExecutor(processOutput);

            // create command line without any arguments
            final CommandLine commandLine = new CommandLine(command);

            if (ArrayUtils.isNotEmpty(args)) {
                // add command arguments
                commandLine.addArguments(args);
            }
            int exitValue = -1;

            try {
                // execute command
                exitValue = executor.execute(commandLine);
            } catch (IOException e) {
                // ignore exception
            }

            if (!executor.isFailure(exitValue)) {
                return processOutput.getOutput();
            }
        }
        return null;
    }

    /**
     * Creates executor with system watchdog for given output stream.
     * 
     * @param outputStream
     * @return
     */
    private static Executor createExecutor(OutputStream outputStream) {

        // create process watchdog with timeout 60000 milliseconds
        ExecuteWatchdog watchdog = new ExecuteWatchdog(WATCHDOG_TIMEOUT);

        // set watchdog and stream handler
        Executor executor = new DefaultExecutor();
        executor.setWatchdog(watchdog);
        executor.setStreamHandler(new PumpStreamHandler(outputStream, outputStream));
        return executor;
    }
}