Tuesday, February 20, 2018

JDK 10: Accessing Java Application's Process ID from Java

A popular question on StackOverflow.com is, "How can a Java program get its own process ID?" There are several answers associated with that question that include parsing the String returned by ManagementFactory.getRuntimeMXBean().getName() [but that can provide an "arbitrary string"], using ProcessHandle.getPid() [JEP 102], using Java Native Access (JNA), using System Information Gatherer And Reporter (SIGAR), using JavaSysMon, using Java Native Runtime - POSIX, parsing the results of jps (or jcmd) via invocation of Runtime.getRuntime().exec(String), and other approaches. JDK 10 introduces perhaps the easiest approach of all for obtaining a JVM process's PID via a new method on the RuntimeMXBean.

JDK-8189091 ("MBean access to the PID") introduces the RuntimeMXBean method getPid() as a default interface method with JDK 10. That issue states the "Problem" as: "The platform MBean does not provide any API to get the process ID of a running JVM. Some JMX tools rely on the hotspot implementation of RuntimeMXBean::getName which returns < pid >@< hostname >." The issue also provides the "Solution": "Introduced new API java.lang.management.RuntimeMXBean.getPid, so that JMX tools can directly get process ID instead of relying on the implementation detail, RuntimeMXBean#getName().split("@")[0]."

The next code listing is a simple one and it demonstrates use of this new getPid() method on RuntimeMXBean.

Using JDK 10's RuntimeMXBean.getPid()

final RuntimeMXBean runtime = ManagementFactory.getRuntimeMXBean();
final long pid = runtime.getPid();
final Console console = System.console();
out.println("Process ID is '" + pid + "' Press <ENTER> to continue.");

When the code above is contained within an executable main(String[]) function and that function is executed from the command line, the output is as shown in the next screen snapshot (which also includes a separate terminal used to verify the PID is correct via jcmd).

The process ID is provided as a long and no parsing of an "arbitrary string" is necessary. This approach also does not require a third-party library or elaborate code to determine the current Java process's identifier.

This post has provided a brief introduction to what will perhaps be the easiest approach for a Java application (written with JDK 10 or later) to determine its own underlying process ID.

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