Launches a process, redirecting the output of that sub-process to the output of this (the parent) process.
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Launches a process, redirecting the output of that sub-process to the output
* of this (the parent) process.
*
* @author Klaas Waslander
*/
public final class ProcessLauncher {
/** the logger for this class */
private final static Logger LOGGER = Logger.getLogger(ProcessLauncher.class.getName());
private String commandLine;
private String[] commandArray;
private File baseDir;
private ArrayList listeners = new ArrayList(1);
private Process subProcess;
private boolean finished = false;
StringBuffer out = new StringBuffer();
StringBuffer err = new StringBuffer();
/**
* Constructs new process launcher with the given command line.
*/
public ProcessLauncher(String commandLine) {
this(commandLine, null);
}
public ProcessLauncher(String commandLine, File baseDir) {
this.commandLine = commandLine;
this.baseDir = baseDir;
}
/**
* Constructs new process launcher with the given command array.
*/
public ProcessLauncher(String[] commandArray) {
this(commandArray, null);
}
public ProcessLauncher(String[] commandArray, File baseDir) {
this.commandArray = commandArray;
this.baseDir = baseDir;
}
/**
* Constructs new process launcher with the given command element list.
*/
public ProcessLauncher(ArrayList commandList) {
this(commandList, null);
}
public ProcessLauncher(ArrayList commandList, File baseDir) {
this(toStringArray(commandList), baseDir);
}
private static String[] toStringArray(ArrayList list) {
String[] result = new String[list.size()];
Iterator iter = list.iterator();
int arrayIndex = 0;
while (iter.hasNext()) {
result[arrayIndex++] = iter.next().toString();
}
return result;
}
/**
* Classes implementing this interface can receive output generated by
* processes launched using the ProcessLauncher.
*/
public interface OutputListener {
public void standardOutput(char[] output);
public void errorOutput(char[] output);
}
/**
* Add a listener for output from the to-be-launched process.
*/
public void addOutputListener(OutputListener listener) {
this.listeners.add(listener);
}
/** fire error output event */
private void fireErr(char[] err) {
if (this.listeners.isEmpty()) {
this.err.append(out);
}
Iterator iter = this.listeners.iterator();
while (iter.hasNext()) {
((OutputListener) iter.next()).errorOutput(err);
}
}
/** fire standard output event */
private void fireOut(char[] out) {
if (this.listeners.isEmpty()) {
this.out.append(out);
}
Iterator iter = this.listeners.iterator();
while (iter.hasNext()) {
((OutputListener) iter.next()).standardOutput(out);
}
}
/**
* Get standard output, in case no listeners were registered - never returns
* null.
*/
public String getStandardOutput() {
if (!this.listeners.isEmpty()) {
throw new IllegalStateException(
"Cannot get standard output, because outputlisteners have been registered.");
}
return this.out.toString();
}
/**
* Get error output, in case no listeners were registered - never returns
* null.
*/
public String getErrorOutput() {
if (!this.listeners.isEmpty()) {
throw new IllegalStateException(
"Cannot get error output, because outputlisteners have been registered.");
}
return this.err.toString();
}
/**
* Get the commandline that is used to launch the process.
*/
public String getCommandLine() {
String usedCommand = this.commandLine;
if (this.commandLine == null && this.commandArray != null) {
usedCommand = "";
for (int i = 0; i < this.commandArray.length; i++) {
if (i > 0) {
usedCommand += " ";
}
usedCommand += this.commandArray[i];
}
}
return usedCommand;
}
/**
* Check whether execution has finished.
*/
public boolean hasFinished() {
return finished;
}
/**
* Launches the process, and blocks until that process completes execution.
*
* @throws CommandNotExistsException
* If the command could not be executed because it does not exist
*/
public int launch() throws CommandNotExistsException {
this.err.setLength(0);
this.out.setLength(0);
BackgroundPrinter stdout = null;
BackgroundPrinter stderr = null;
try {
if (this.commandArray != null) {
this.subProcess = Runtime.getRuntime().exec(this.commandArray, null, this.baseDir);
} else {
this.subProcess = Runtime.getRuntime().exec(this.commandLine, null, this.baseDir);
}
stdout = new BackgroundPrinter(subProcess.getInputStream(), false);
stderr = new BackgroundPrinter(subProcess.getErrorStream(), true);
stdout.start();
stderr.start();
// kill process and wait max 10 seconds for output to complete
int exitValue = this.subProcess.waitFor();
stdout.join(10000);
stderr.join(10000);
/*
* if (exitValue != 0) { LOGGER.fine("WARNING: exit value " + exitValue + "
* for command \"" + getCommandLine() + "\""); }
*/
return exitValue;
} catch (IOException ioe) {
// usually caused if the command does not exist at all
throw new CommandNotExistsException("Command probably does not exist: " + ioe);
} catch (Exception e) {
LOGGER
.log(Level.SEVERE, "Exception while running/launching \"" + getCommandLine() + "\".", e);
} finally {
if (this.subProcess != null) {
this.subProcess.destroy();
this.subProcess = null;
}
if (stdout != null) {
stdout.close();
}
if (stderr != null) {
stderr.close();
}
this.finished = true;
}
return -1;
}
/**
* Tries to abort the currently running process.
*/
public void abort() {
if (this.subProcess != null) {
this.subProcess.destroy();
this.subProcess = null;
}
}
/**
* Catches output from a "java.lang.Process" and writes it to either
* System.err or System.out.
*
* @author Klaas Waslander - Sun Java Center
*/
private class BackgroundPrinter extends Thread {
private InputStream in;
boolean isErrorOutput;
public BackgroundPrinter(InputStream in, boolean isErrorOutput) {
this.in = in;
this.isErrorOutput = isErrorOutput;
}
public void run() {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(this.in));
// read buffer
char[] buf = new char[1024];
// write data to target, until no more data is left to read
int numberOfReadBytes;
while ((numberOfReadBytes = reader.read(buf)) != -1) {
char[] clearedbuf = new char[numberOfReadBytes];
System.arraycopy(buf, 0, clearedbuf, 0, numberOfReadBytes);
if (this.isErrorOutput) {
fireErr(clearedbuf);
} else {
fireOut(clearedbuf);
}
}
/*
* } catch (IOException ioe) { // ignore this: process has ended,
* causing IOException } catch (NullPointerException ioe) { // ignore
* this: there was no resulting output
*/
} catch (Exception e) {
LOGGER.log(Level.FINE, "Exception while reading from stream from subprocess.", e);
}
}
public void close() {
try {
this.in.close();
} catch (Exception e) {
LOGGER.log(Level.WARNING,
"Closing background stream for launched process caused exception.", e);
}
}
}
/**
* Exception that is thrown when a command could not be executed because it
* (probably) does not exist at all.
*
* @author Klaas Waslander
*/
public static class CommandNotExistsException extends RuntimeException {
/**
* Construct a new exception for a command that does not exist.
*
* @param msg
* The message for this exception.
*/
public CommandNotExistsException(String msg) {
super(msg);
}
}
}
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