alma.acs.util

Class ProcessStreamGobbler

java.lang.Object

alma.acs.util.ProcessStreamGobbler

public class ProcessStreamGobbler
extends java.lang.Object

Continuously reads the stdout and stderr streams of Process in separate threads, so that the OS will not block out the JVM, as it could otherwise happen if lines are read from these streams sequentially in one thread.

This class is only useful if the external process's output is either not interesting at all for the user, or if the output should be read only after the process has terminated. Otherwise the streams should be read directly without using this class.

The gobble(long, TimeUnit) call returns either when both stdout and stderr streams deliver a null, or if the timeout is reached. @TODO check if relying on the null from both streams is as robust as Process.waitFor().

Author:

hsommer

Constructor Summary

Constructors

Constructor and Description
ProcessStreamGobbler(java.lang.Process proc, java.util.concurrent.ThreadFactory tf, boolean storeStreamContent)

Method Summary

Modifier and Type	Method and Description
java.util.List<java.lang.String>	getStderr() Returns the stderr data read, or null if storeStreamContent==false
java.util.List<java.lang.String>	getStdout() Returns the stdout data read, or null if storeStreamContent==false
boolean	gobble(long timeout, java.util.concurrent.TimeUnit unit) Starts fetching process output from stdout/stderr, storing it internally so that it can later be read via getStdout() and getStderr().
void	gobbleAsync() Starts fetching process output from stdout/stderr, storing it internally so that it can later be read via getStdout() and getStderr().
boolean	hasStreamReadErrors()
boolean	hasTerminated()
void	setDebug(boolean DEBUG)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ProcessStreamGobbler

public ProcessStreamGobbler(java.lang.Process proc,
                            java.util.concurrent.ThreadFactory tf,
                            boolean storeStreamContent)

Parameters:

proc - The process whose streams we want to read.

tf - ThreadFactory to be used to create the two threads that read the stdout and stderr streams

storeStreamContent - If true, then the stdout and stderr content will be stored and can be read using getStdout() and getStderr()

Method Detail

gobbleAsync

public void gobbleAsync()

Starts fetching process output from stdout/stderr, storing it internally so that it can later be read via getStdout() and getStderr().

Use this method if you do not want to wait for the process to end. The status can anyway be checked using hasTerminated().

gobble

public boolean gobble(long timeout,
                      java.util.concurrent.TimeUnit unit)
               throws java.lang.InterruptedException

Starts fetching process output from stdout/stderr, storing it internally so that it can later be read via getStdout() and getStderr().

Use this method if you want to wait for the process to end, limited by a timeout.

Parameters:

timeout - maximum time to wait for the process to finish

unit - unit for the timeout

Returns:

true if returning because the process ended, otherwise false if the timeout applied (in which case the streams will continue to be read though).

Throws:

java.lang.InterruptedException

getStdout

public java.util.List<java.lang.String> getStdout()

Returns the stdout data read, or null if storeStreamContent==false

getStderr

public java.util.List<java.lang.String> getStderr()

Returns the stderr data read, or null if storeStreamContent==false

hasStreamReadErrors

public boolean hasStreamReadErrors()

Returns:

true if there was 1 or more errors reading the stdout or stderr stream.

Throws:

java.lang.IllegalStateException - if called before gobble(long, TimeUnit) or gobbleAsync().

hasTerminated

public boolean hasTerminated()

setDebug

public void setDebug(boolean DEBUG)