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A lightweight library to execute external processes from Java.
/*
* Copyright (C) 2014 ZeroTurnaround
* Contains fragments of code from Apache Commons Exec, rights owned
* by Apache Software Foundation (ASF).
*
* 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.
*
* NOTICE: This file originates from the Apache Commons Exec package.
* It has been modified to fit our needs.
*
* The following is the original header of the file in Apache Commons Exec:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.zeroturnaround.exec.stream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Map;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.MDC;
import org.zeroturnaround.exec.MDCRunnableAdapter;
/**
* Copies standard output and error of subprocesses to standard output and error
* of the parent process. If output or error stream are set to null, any feedback
* from that stream will be lost.
*/
public class PumpStreamHandler implements ExecuteStreamHandler {
private static final Logger log = LoggerFactory.getLogger(PumpStreamHandler.class);
protected Thread outputThread;
protected Thread errorThread;
protected Thread inputThread;
protected final OutputStream out;
protected final OutputStream err;
protected final InputStream input;
protected InputStreamPumper inputStreamPumper;
/**
* Construct a new PumpStreamHandler.
*/
public PumpStreamHandler() {
this(System.out, System.err);
}
/**
* Construct a new PumpStreamHandler.
*
* @param outAndErr
* the output/error OutputStream.
*/
public PumpStreamHandler(OutputStream outAndErr) {
this(outAndErr, outAndErr);
}
/**
* Construct a new PumpStreamHandler.
*
* @param out
* the output OutputStream.
* @param err
* the error OutputStream.
*/
public PumpStreamHandler(OutputStream out, OutputStream err) {
this(out, err, null);
}
/**
* Construct a new PumpStreamHandler.
*
* @param out
* the output OutputStream.
* @param err
* the error OutputStream.
* @param input
* the input InputStream.
*/
public PumpStreamHandler(OutputStream out, OutputStream err, InputStream input) {
this.out = out;
this.err = err;
this.input = input;
}
/**
* Set the InputStream from which to read the standard output
* of the process.
*
* @param is
* the InputStream.
*/
public void setProcessOutputStream(InputStream is) {
if (out != null) {
createProcessOutputPump(is, out);
}
}
/**
* Set the InputStream from which to read the standard error
* of the process.
*
* @param is
* the InputStream.
*/
public void setProcessErrorStream(InputStream is) {
if (err != null) {
createProcessErrorPump(is, err);
}
}
/**
* Set the OutputStream by means of which input can be sent
* to the process.
*
* @param os
* the OutputStream.
*/
public void setProcessInputStream(OutputStream os) {
if (input != null) {
if (input == System.in) {
inputThread = createSystemInPump(input, os);
}
else {
inputThread = createPump(input, os, true, true);
}
}
else {
try {
os.close();
}
catch (IOException e) {
log.info("Got exception while closing output stream", e);
}
}
}
/**
* Start the Threads.
*/
public void start() {
if (outputThread != null) {
outputThread.start();
}
if (errorThread != null) {
errorThread.start();
}
if (inputThread != null) {
inputThread.start();
}
}
/**
* Stop pumping the streams.
*/
public void stop() {
if (inputThread != null) {
if (inputStreamPumper != null) {
inputStreamPumper.stopProcessing();
}
// #33 Interrupt reading from a PipedInputStream to unblock the pumping thread
inputThread.interrupt();
log.trace("Joining input thread {}...", inputThread);
try {
inputThread.join();
inputThread = null;
}
catch (InterruptedException e) {
// ignore
}
}
if (outputThread != null) {
log.trace("Joining output thread {}...", outputThread);
try {
outputThread.join();
outputThread = null;
}
catch (InterruptedException e) {
// ignore
}
}
if (errorThread != null) {
log.trace("Joining error thread {}...", errorThread);
try {
errorThread.join();
errorThread = null;
}
catch (InterruptedException e) {
// ignore
}
}
flush();
}
public void flush() {
if (out != null) {
log.trace("Flushing output stream {}...", out);
try {
out.flush();
}
catch (IOException e) {
log.error("Got exception while flushing the output stream", e);
}
}
if (err != null && err != out) {
log.trace("Flushing error stream {}...", err);
try {
err.flush();
}
catch (IOException e) {
log.error("Got exception while flushing the error stream", e);
}
}
}
/**
* Get the output stream.
*
* @return OutputStream.
*/
public OutputStream getOut() {
return out;
}
/**
* Get the error stream.
*
* @return OutputStream.
*/
public OutputStream getErr() {
return err;
}
/**
* Get the input stream.
*
* @return InputStream.
*/
public InputStream getInput() {
return input;
}
/**
* Create the pump to handle process output.
*
* @param is
* the InputStream.
* @param os
* the OutputStream.
*/
protected void createProcessOutputPump(InputStream is, OutputStream os) {
outputThread = createPump(is, os);
}
/**
* Create the pump to handle error output.
*
* @param is
* the InputStream.
* @param os
* the OutputStream.
*/
protected void createProcessErrorPump(InputStream is, OutputStream os) {
errorThread = createPump(is, os);
}
/**
* Creates a stream pumper to copy the given input stream to the given
* output stream.
*
* @param is the input stream to copy from
* @param os the output stream to copy into
* @return the stream pumper thread
*/
protected Thread createPump(InputStream is, OutputStream os) {
return createPump(is, os, false, false);
}
/**
* Creates a stream pumper to copy the given input stream to the given
* output stream.
*
* @param is the input stream to copy from
* @param os the output stream to copy into
* @param closeWhenExhausted close the output stream when the input stream is exhausted
* @return the stream pumper thread
*/
protected Thread createPump(InputStream is, OutputStream os, boolean closeWhenExhausted) {
return createPump(is, os, closeWhenExhausted, false);
}
/**
* Creates a stream pumper to copy the given input stream to the given
* output stream.
*
* @param is the input stream to copy from
* @param os the output stream to copy into
* @param closeWhenExhausted close the output stream when the input stream is exhausted
* @param flushImmediately flush the output stream whenever data was written to it
* @return the stream pumper thread
*/
protected Thread createPump(InputStream is, OutputStream os, boolean closeWhenExhausted, boolean flushImmediately) {
return newThread(new StreamPumper(is, os, closeWhenExhausted, flushImmediately));
}
/**
* Creates a stream pumper to copy the given input stream to the given
* output stream.
*
* @param is the System.in input stream to copy from
* @param os the output stream to copy into
* @return the stream pumper thread
*/
protected Thread createSystemInPump(InputStream is, OutputStream os) {
inputStreamPumper = new InputStreamPumper(is, os);
return newThread(inputStreamPumper);
}
/**
* Override this to customize how the background task is created.
*
* @param task the task to be run in the background
* @return the thread of the task
*/
protected Thread newThread(Runnable task) {
Thread result = new Thread(wrapTask(task));
result.setDaemon(true);
return result;
}
/**
* Override this to customize how the background task is created.
*
* @param task the task to be run in the background
* @return the runnable of the wrapped task
*/
protected Runnable wrapTask(Runnable task) {
// Preserve the MDC context of the caller thread.
Map contextMap = MDC.getCopyOfContextMap();
if (contextMap != null) {
return new MDCRunnableAdapter(task, contextMap);
}
return task;
}
}