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
mvn packagejava -cp target\example.processhandle.jar;target\lib\* example.App --action powershell --wait 30000This 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 $info.id) | out-file -FilePath 'C:\TEMP\a123.txt' -encoding ascii; }"
2021-09-19 18:41:39 [main] - INFO Waiting for 30000 millisecond
2021-09-19 18:42:09 [main] - INFO C:\TEMP\pidfile.txt data:2832
2021-09-19 18:42:09 [main] - INFO is alive: true
2021-09-19 18:42:20 [main] - INFO Running the command: [cmd, /c, tasklist /FI "PID eq 2832"]
2021-09-19 18:42:29 [main] - INFO is alive (Windows version): true
2021-09-19 18:42:49 [main] - INFO Killing the process pid: 28322021-09-19 18:42:09 [main] - INFO Killing the process pid: 2832
NOTE the doubled commas in the `ProcessBuilder arguments` above is expected - needed to build Powershell's `start-process` `ArgumentListt` part:
```cmd
Start-Process [-FilePath] <string> [[-ArgumentList] <string[]>]
[-WorkingDirectory <string>] [-PassThru] [-Verb <string>] [-WindowStyle
<ProcessWindowStyle> {Normal | Hidden | Minimized | Maximized}] [-Wait]
[<CommonParameters>]
An alternative option (WIP) is to use invoke-expression
Due to the limitations of simulating a POSIX environment under Windows, there is little information one can get from built-in ps command. In particular no command line args.
To get that, use the following Powershell command from cygwin:
PID=956
powershell.exe '&{$id = $args[0]; $o = Get-CimInstance Win32_Process -Filter ("processid = {0}" -f $id ); $o.CommandLine }' $PIDNOTE: Cannot use variable $pid because variable PID because it is special,
read-only or constant and script would fail detecting attempt to override it
this will print
"C:\java\jdk1.8.0_101\bin\java.exe" -cp target\example.processhandle.jar;target\lib\* -Xms512m -Xmx512m example.Dialog
NOTE: Unrecognized option e.g. -Xmm512m will lead to hard to debug failures
* launch
```cmd
java -cp target\example.processhandle.jar;target\lib\* example.App -a powershell -w 5000 -file %TEMP%\pidfile.txt
NOTE: specify the pid file path, using Windows environment notation e.g. %TEMP%
- when run un debug mode
java -cp target\example.processhandle.jar;target\lib\* example.App --debug --action powershell --wait 30000 it will log some Powerhell settings to debug log file:
type c:\temp\debug.logwill display something like
currentdir: C:\developer\sergueik\selenium_java\basic-processhandle
path:C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\local\bin;C:\Program Files\Git\usr\bin;C:\Program Files\Git\usr\bin;C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\bin;C:\Users\sergueik\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0;c:\java\zulu11.45.27-ca-jdk11.0.10-win_x64\bin
without --debug flag there will be no logging
can not use the XML comment:
[ERROR] Non-parseable POM c:\developer\sergueik\selenium_java\basic-processhandle\pom.xml: in comment after two dashes (--) next character must be > not r ( position: END_TAG seen ...<target>${java.version}</target>\r\n<!-- invalid flag:
--r... @85:23) @ line 85, column 23 -> [Help 2]
When developing the code one may use a longer version of the Poweshell Process Creation helper snippet, e.g.
[System.Diagnostics.ProcessStartInfo] $startInfo = new-object System.Diagnostics.ProcessStartInfo
$startInfo.FileName = 'java.exe'
$startInfo.Arguments = ('-cp target\example.processhandle.jar;target\lib\* example.Dialog >> {0}' -f $logfile )
$startInfo.UseShellExecute = $true
# NOTE: The Process object must have the UseShellExecute property set to false in order to redirect IO streams.
$startInfo.RedirectStandardOutput = $false
$startInfo.WorkingDirectory = $process_workdir
$startInfo.WindowStyle = [System.Diagnostics.ProcessWindowStyle]::Hidden
$startInfo.ErrorDialog = $true
[System.Diagnostics.Process] $process = [System.Diagnostics.Process]::Start($startInfo)
# TODO: improve wait until exited
while (-not $process.HasExited) {
start-sleep -seconds 1
}
get-content -path "${process_workdir}\${logfile}"
if there is an error reported by Java code in the console
Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.base/java.lang.Integer.parseInt(Integer.java:662)
at java.base/java.lang.Integer.parseInt(Integer.java:770)
at example.Launcher.getPid(Launcher.java:173)
at example.App.main(App.java:106)
which is because there is no PID information in the pid file C:\TEMP\pidfile.txt:
Pid=
to find the root cause, extract and run directly the command from the log:
2024-03-21 14:40:48 [main] - INFO Launching command: powershell.exe /noprofile /executionpolicy bypass "&{ $o = new-object System.Diagnostics.ProcessStartInfo;$o.FileName = 'java.exe';$o.Arguments = ' -cp target\example.processhandle.jar;target\lib\* example.Dialog';$o.UseShellExecute = $false;$o.RedirectStandardOutput = $false;$o.WindowStyle = [System.Diagnostics.ProcessWindowStyle]::Hidden;$o.ErrorDialog = $false;$o.PriorityClass=System.Diagnostics.ProcessPriorityClass]::BelowNormal; $p = [System.Diagnostics.Process]::Start($o);while ($p.ID -eq 0) {start-sleep -millisecond 100;}write-output ('Pid={0}' -f $p.Id) | out-file -LiteralPath 'C:\TEMP\pidfile.txt' -encoding ascii; }"The command will be
powershell.exe /noprofile /executionpolicy bypass "&{ $o = new-object System.Diagnostics.ProcessStartInfo;$o.FileName = 'java.exe';$o.Arguments = ' -cp target\example.processhandle.jar;target\lib\* example.Dialog';$o.UseShellExecute = $false;$o.RedirectStandardOutput = $false;$o.WindowStyle = [System.Diagnostics.ProcessWindowStyle]::Hidden;$o.ErrorDialog = $false;$p = [System.Diagnostics.Process]::Start($o);$p.PriorityClass=System.Diagnostics.ProcessPriorityClass]::BelowNormal; while ($p.Id -eq 0) {start-sleep -millisecond 100;}write-output ('Pid={0}' -f $p.Id) | out-file -LiteralPath 'C:\T EMP\pidfile.txt' -encoding ascii; }"the error will be displayed in clear text in the console output e.g.
Exception calling "Start" with "1" argument(s): "The system cannot find the file specified"
At line:1 char:316
or
System.Diagnostics.ProcessPriorityClass]::BelowNormal : The term
'System.Diagnostics.ProcessPriorityClass]::BelowNormal' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
when JDK from the path containg special characters is used. using quotes in the evvironment variables corrupts the path
JAVA_HOME="c:\java\jdk-11.0.12+7"this leads to weird error:
where.exe javaINFO: Could not find files for the given pattern(s).
java -versionopenjdk version "11.0.12" 2021-07-20
OpenJDK Runtime Environment Temurin-11.0.12+7 (build 11.0.12+7)
OpenJDK Client VM Temurin-11.0.12+7 (build 11.0.12+7, mixed mode)
* 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)