Master Spring Boot 3 Actuator: Custom Endpoints, Health Checks, and Monitoring

Introduction

Spring Boot provides many additional features that help you monitor and manage applications in production. The Actuator module exposes built‑in endpoints (e.g., /health ) and allows you to add custom ones.

Maven dependency:

<code>&lt;dependency&gt;
  &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
  &lt;artifactId&gt;spring-boot-starter-actuator&lt;/artifactId&gt;
&lt;/dependency&gt;</code>

Powerful Features

2.1 CORS Support

<code>management:
  endpoints:
    web:
      cors:
        allow-credentials: true
        allowed-headers: '*'
        allowed-origins: ''</code>

2.2 Custom Endpoint

<code>@Component
@Endpoint(id = "pack")
public class PackEndpoint {

  @ReadOperation
  public CustomData getData() {
    return new CustomData("Custom Endpoint");
  }

  @WriteOperation
  public void writeData(String title) {
    System.out.printf("修改标题：%s%n", title);
  }

  static class CustomData {
    private String title;
    public CustomData(String title) { this.title = title; }
    public String getTitle() { return title; }
    public void setTitle(String title) { this.title = title; }
  }
}</code>

2.3 Application Health Information

Default /health response shows basic status. To display detailed information, add:

<code>management:
  endpoint:
    health:
      show-details: always</code>

You can also enable or disable specific health indicators, e.g.:

<code>management:
  endpoint:
    health:
      show-details: always
  health:
    db:
      enabled: false
    diskspace:
      enabled: true</code>

Role‑based detail exposure:

<code>management:
  endpoint:
    health:
      show-details: when-authorized
      roles:
        - ROLE_ADMIN</code>

2.4 Custom Health Indicator

<code>@Component
public class PackHealthIndicator implements HealthIndicator {
  @Override
  public Health health() {
    int errorCode = check();
    if (errorCode != 0) {
      return Health.down().withDetail("Error Code", errorCode).build();
    }
    return Health.up().build();
  }

  private int check() {
    return new Random().nextInt(2);
  }
}</code>

After adding this bean, /health will return {"status":"UP"} or {"status":"DOWN", "details":{...}} accordingly.

2.5 HTTP Request Tracing

Enable tracing by defining an HttpTraceRepository bean, e.g. the in‑memory implementation:

<code>@Bean
InMemoryHttpTraceRepository inMemoryHttpTraceRepository() {
  return new InMemoryHttpTraceRepository();
}</code>

Access traces via /httptrace . You can refine what is recorded:

<code>management:
  trace:
    http:
      include:
        - request-headers
        - response-headers</code>

2.6 Security Auditing

When Spring Security is on the classpath, Actuator provides an audit framework. Enable it by providing an AuditEventRepository bean:

<code>@Bean
SecurityFilterChain actuatorSecurityFilterChain(HttpSecurity http) throws Exception {
  http.csrf(csrf -> csrf.disable());
  http.authorizeHttpRequests().antMatchers("/ac/**").hasRole("ACTUATOR");
  http.authorizeHttpRequests().anyRequest().permitAll();
  http.formLogin(customizer -> Customizer.withDefaults());
  return http.build();
}

@Bean
InMemoryAuditEventRepository auditEventRepository() {
  return new InMemoryAuditEventRepository();
}</code>

2.7 Process Monitoring

Spring Boot can write process‑related files:

ApplicationPidFileWriter : creates application.pid containing the JVM PID.

WebServerPortFileWriter : creates application.port with the server’s listening port.

Add the following line to META-INF/spring.factories :

<code>org.springframework.context.ApplicationListener=\
org.springframework.boot.context.ApplicationPidFileWriter,\
org.springframework.boot.web.context.WebServerPortFileWriter</code>

After starting the application, the files appear in the project’s root directory.