how to use java jps

Daniel Parker

3 min read

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15-01-2025

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The Java Virtual Machine (JVM) is the heart of any Java application. Understanding its processes is crucial for developers. One invaluable tool for this is jps, the Java Virtual Machine Process Status Tool. This article provides a comprehensive guide on how to effectively use jps to monitor and manage your Java processes. We'll explore its basic functionality and delve into advanced usage scenarios.

What is jps?

jps (Java Virtual Machine Process Status Tool) is a command-line utility included in the Java Development Kit (JDK). Its primary function is to list the Java Virtual Machines (JVMs) currently running on your system. This simple yet powerful tool is essential for troubleshooting, monitoring, and managing Java applications.

Basic Usage of jps

The simplest way to use jps is to simply type jps into your terminal or command prompt. This will list all the JVMs running, displaying their process IDs (PIDs). Each line shows the PID and the main class name or JAR file name of the running application.

jps

Example Output:

1234 MainClass
4567 MyApplication.jar
7890 MyApp

Here, 1234, 4567, and 7890 are the process IDs of the running Java applications.

Advanced jps Options

jps offers several options to refine its output and tailor it to specific needs.

-l (Long Listing)

The -l option provides a long listing, showing the full path of the JAR file or the main class name. This is particularly helpful when dealing with many applications or complex setups.

jps -l

Example Output:

1234 /path/to/my/app/MainClass.jar
4567 /usr/local/myapp/MyApplication.jar
7890 com.example.MyApp

-m (Print Main Method Arguments)

The -m option displays the main method arguments passed to each JVM. This is useful for debugging or understanding how a particular application was launched.

jps -m

Example Output: (Illustrative, arguments will vary based on application)

1234 MainClass arg1 arg2
4567 MyApplication.jar -config config.xml -port 8080

-v (Print JVM Arguments)

This option lists the JVM arguments used to launch each process. This information is crucial for understanding JVM configuration and potential performance issues.

jps -v

Example Output: (Illustrative, arguments will vary)

1234 MainClass -Xms128m -Xmx512m -XX:+UseG1GC

-q (Quiet Mode)

The -q option suppresses the output of the class name or JAR file, displaying only the PIDs.

jps -q

Example Output:

1234
4567
7890

-V (Print Full VM Arguments)

The -V option gives even more details about the JVM arguments than -v. It's useful for advanced troubleshooting scenarios.

Combining Options

You can combine these options to get the most detailed information. For instance, jps -lvm will show the full path, main method arguments, and JVM arguments for each process.

Troubleshooting with jps

jps is invaluable for troubleshooting. If an application crashes, you can use jps to confirm it's no longer running or to identify its PID for further investigation using other tools like jstack or jmap.

jps and Remote JVMs

While jps primarily targets local JVMs, with some configuration it can be used to monitor remote JVMs using JMX. This requires setting up JMX remotely and then using appropriate flags with jps. This is a more advanced topic and typically involves specifying a hostname and port. Consult the official Java documentation for details on configuring and using JMX.

Conclusion

jps is a fundamental tool for any Java developer. Its simplicity and power make it an indispensable asset for monitoring, managing, and troubleshooting Java applications. By mastering the different options and combining them effectively, developers can gain valuable insights into the health and performance of their JVM processes. Remember to consult the official Java documentation for the most up-to-date information and detailed explanations.