How to Persist Spring Boot Application PID to a File (Step‑by‑Step Guide)

1. Introduction

Welcome to the Spring Boot 2 practical series. The PID (Process ID) is a unique identifier assigned by the operating system to each process. It is used in system operations such as kill -9 <pid>.

2. Spring Boot Application Process

The jps command lists all Java processes, their main class or JAR name, and JVM arguments. A Spring Boot application runs as a Java process and therefore has a PID, which can be seen in the startup log, e.g.:

2019-11-20 14:28:00.925  INFO 7828 --- [           main] c.f.s.s.SecurityLearningApplication : Starting SecurityLearningApplication on DESKTOP-L0IOI2S with PID 7828

When multiple Spring Boot applications run, distinguishing their PIDs becomes difficult, so persisting the PID to a file simplifies management.

3. Writing Spring Boot PID to a File

Spring Boot provides ApplicationPidFileWriter to write the PID to a file (default application.pid) at startup. If writing fails, the PID is stored in the system property PID_FAIL_ON_WRITE_ERROR or the Spring environment property spring.pid.fail-on-write-error.

3.1 Configuring PID Persistence

By default ApplicationPidFileWriter is not auto‑configured; you must register it manually in the main class:

package cn.felord.spring.security;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.ApplicationPidFileWriter;
import org.springframework.cache.annotation.EnableCaching;

/**
 * @author Felordcn
 */
@SpringBootApplication
public class SecurityLearningApplication {

    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(SecurityLearningApplication.class);
        springApplication.addListeners(new ApplicationPidFileWriter());
        springApplication.run(args);
    }
}

After this configuration, the application creates application.pid containing the PID. You can customize the file name and location with the property spring.pid.file:

spring:
  pid:
    file: /var/run/myApp.pid

Restarting the application will generate /var/run/myApp.pid with the current PID.

4. Conclusion

This article explained how to persist a Spring Boot application's PID to a file using programmatic configuration. You can customize the storage file path and name as needed.