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README.md

Info

launch capture

This directory contains example code to launch the java jar in background process and get the process PID. The Java 11 ProcessHandle.of method was found to be unreliable, so th get the Java process pid, a small inline Powershell script is launched and java PID is written to a pidfile by that script allowing the calling Java program to read the pid.

The jna is still added the dependencies to have the legacy JNA based code snippets for

examples available in the same application for comparison

Usage

mvn package
java -cp target\example.processhandle.jar;target\lib\* example.App --action powershell --wait 30000

This will launch a mini Swing App to test itself. It passes a lot of Java options (to test ability). It waits a litle bit (configurable) then reads the java process PID from pidfile and kills that process. It will log the following to the console:

2021-09-19 18:41:39  [main] - INFO  processing command: java.exe -cp target\example.processhandle.jar;target\lib\* -XX:+UseG1GC -Xms512m -Xmx512m -XX:ParallelGCThreads=6 -Xlog:gc* -XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default example.Dialog
2021-09-19 18:41:39  [main] - INFO  New Command Arguments:['-cp', 'target\example.processhandle.jar;target\lib\*', '-XX:+UseG1GC', '-Xms512m', '-Xmx512m', '-XX:ParallelGCThreads=6', '-Xlog:gc*', '-XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default', 'example.Dialog']
2021-09-19 18:41:39  [main] - INFO  New Command: "-filepath 'java.exe' -argumentlist '-cp', 'target\example.processhandle.jar;target\lib\*', '-XX:+UseG1GC', '-Xms512m', '-Xmx512m', '-XX:ParallelGCThreads=6', '-Xlog:gc*', '-XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default', 'example.Dialog'"
2021-09-19 18:41:39  [main] - INFO  processing command: java.exe -cp target\example.processhandle.jar;target\lib\* -XX:+UseG1GC -Xms512m -Xmx512m -XX:ParallelGCThreads=6 -Xlog:gc* -XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default example.Dialog
2021-09-19 18:41:39  [main] - INFO  New Command Arguments:['-cp', 'target\example.processhandle.jar;target\lib\*', '-XX:+UseG1GC', '-Xms512m', '-Xmx512m', '-XX:ParallelGCThreads=6', '-Xlog:gc*', '-XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default', 'example.Dialog']
2021-09-19 18:41:39  [main] - INFO  New Command: "-filepath 'java.exe' -argumentlist '-cp', 'target\example.processhandle.jar;target\lib\*', '-XX:+UseG1GC', '-Xms512m', '-Xmx512m', '-XX:ParallelGCThreads=6', '-Xlog:gc*', '-XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default', 'example.Dialog'"
2021-09-19 18:41:39  [main] - INFO  ProcessBuilder arguments: 
powershell.exe,
/noprofile,
/executionpolicy,
bypass,
"&{,
$info,
=,
start-process,
-filepath,
'java.exe',
-argumentlist,
'-cp',,
'target\example.processhandle.jar;target\lib\*',,
'-XX:+UseG1GC',,
'-Xms512m',,
'-Xmx512m',,
'-XX:ParallelGCThreads=6',,
'-Xlog:gc*',,
'-XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default',,
'example.Dialog',
-passthru;,
$info.PriorityClass=[System.Diagnostics.ProcessPriorityClass]::BelowNormal;,
write-output,
('Pid={0}',
-f,
$info.id),
|,
out-file,
-FilePath,
'C:\TEMP\pidfile.txt',
-encoding,
ascii;,
}"
2021-09-19 18:41:39  [main] - INFO  Launching command: powershell.exe /noprofile /executionpolicy bypass "&{ $info = start-process -filepath 'java.exe' -argumentlist '-cp', 'target\example.processhandle.jar;target\lib\*', '-XX:+UseG1GC', '-Xms512m', '-Xmx512m', '-XX:ParallelGCThreads=6', '-Xlog:gc*', '-XX:StartFlightRecording=disk=true,delay=30s,maxsize=100m,name=continuous,settings=default', 'example.Dialog' -passthru; $info.PriorityClass=[System.Diagnostics.ProcessPriorityClass]::BelowNormal; write-output ('Pid={0}' -f $info.id) | out-file -FilePath 'C:\TEMP\a123.txt' -encoding ascii; }"
2021-09-19 18:41:39  [main] - INFO  Waiting for 30000 millisecond
2021-09-19 18:42:09  [main] - INFO  C:\TEMP\pidfile.txt data:2832
2021-09-19 18:42:09  [main] - INFO  is alive: true
2021-09-19 18:42:09  [main] - INFO  Killing the process pid: 2832

NOTE the doubled commas in the ProcessBuilder arguments above is expected - needed to build Powershell's start-process ArgumentListt part:

    Start-Process [-FilePath] <string> [[-ArgumentList] <string[]>]
    [-WorkingDirectory <string>] [-PassThru] [-Verb <string>] [-WindowStyle
    <ProcessWindowStyle> {Normal | Hidden | Minimized | Maximized}] [-Wait]
    [<CommonParameters>]

An alternative option (WIP) is to use invoke-expression

Testing in Cygwin Environment

Due to the limitations of simulating a POSIX environment under Windows, there is little information one can get from built-in ps command. In particular no command line args.

To get that, use the following Powershell command from cygwin:

PID=956
powershell.exe '&{$id = $args[0]; $o = Get-CimInstance Win32_Process -Filter ("processid = {0}" -f $id ); $o.CommandLine }' $PID

NOTE: Cannot use variable $pid because variable PID because it is special, read-only or constant and script would fail detecting attempt to override it

this will print

"C:\java\jdk1.8.0_101\bin\java.exe" -cp target\example.processhandle.jar;target\lib\* -Xms512m -Xmx512m example.Dialog

NOTE: Unrecognized option e.g. -Xmm512m will lead to hard to debug failures
* launch
```cmd
java -cp target\example.processhandle.jar;target\lib\* example.App -a powershell -w 5000 -file %TEMP%\pidfile.txt

NOTE: specify the pid file path, using Windows environment notation e.g. %TEMP%

Debug Log

  • when run un debug mode
java -cp target\example.processhandle.jar;target\lib\* example.App --debug --action powershell --wait 30000

it will log some Powerhell settings to debug log file:

type c:\temp\debug.log

will display something like

currentdir: C:\developer\sergueik\selenium_java\basic-processhandle
path:C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\local\bin;C:\Program Files\Git\usr\bin;C:\Program Files\Git\usr\bin;C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\bin;C:\Users\sergueik\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0;c:\java\zulu11.45.27-ca-jdk11.0.10-win_x64\bin

without --debug flag there will be no logging

See Aso

* https://docs.oracle.com/javase/9/docs/api/java/lang/ProcessHandle.html
* https://docs.oracle.com/javase/9/docs/api/java/lang/ProcessHandle.Info.html
* https://www.tabnine.com/code/java/methods/com.sun.jna.platform.win32.Kernel32/GetProcessId
* https://www.tabnine.com/code/java/classes/java.lang.ProcessHandle
* https://dev.to/harithay/introduction-to-java-processhandle-5950
* https://www.baeldung.com/java-process-api (legacy)
* https://www.baeldung.com/java-9-process-api (improvements)

Author

Serguei Kouzmine