Monitoring using Actuator

@GetMapping("/actuator/health")
// Automatically provided by Spring Boot Actuator

// 1. Add dependency (pom.xml)
/*
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
*/


// 2. application.properties
management.endpoints.web.exposure.include=*
management.endpoint.health.show-details=always


// 3. Spring Boot Application
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
class ActuatorApp {
  public static void main(String[] args) {
    SpringApplication.run(ActuatorApp.class, args);
  }
}


// 4. Custom Health Indicator
import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;

@Component
class CustomHealthIndicator implements HealthIndicator {

  @Override
  public Health health() {
    boolean dbUp = true;

    if (dbUp) {
      return Health.up().withDetail("Database", "Running").build();
    } else {
      return Health.down().withDetail("Database", "Down").build();
    }
  }
}


// Output Endpoints:
// /actuator/health  -> application health
// /actuator/metrics -> performance metrics
// /actuator/info    -> application info

• 1 Provides production-ready monitoring.
• 2 Exposes health and metrics endpoints.
• 3 Helps in application management.
• 4 Part of Spring Boot ecosystem.

• 1 /actuator/health – application status
• 2 /actuator/metrics – performance metrics
• 3 /actuator/info – application info
• 4 /actuator/env – environment details

• 1 Exposes REST endpoints.
• 2 Collects runtime metrics.
• 3 Monitors application health.
• 4 Integrates with monitoring tools.

• 1 Real-time monitoring
• 2 Production debugging
• 3 Health checks
• 4 System observability

• 1 Used in production monitoring.
• 2 Used in cloud systems.
• 3 Used in microservices observability.
• 4 Used in DevOps dashboards.
• 5 SaaS products use Spring Boot Actuator Monitoring in services, dashboards, background jobs, and API workflows.
• 6 ERP and banking systems apply Spring Boot Actuator Monitoring with validation, logging, review, and rollback plans.
• 7 E-commerce and healthcare platforms use Spring Boot Actuator Monitoring carefully because reliability and data correctness matter.

• 1 A Java program first evaluates the surrounding context, then applies the Spring Boot Actuator Monitoring rules to the current data.
• 2 The important mental model is input, transformation, result, and failure path.
• 3 In production, the same flow usually sits inside a larger layer such as a controller, service, repository, job, or UI component.

• 1 Choose the simplest implementation first, then measure real workloads.
• 2 Watch for repeated work inside loops, unnecessary allocations, and slow I/O in hot paths.
• 3 Prefer clear data structures and stable APIs before micro-optimizing syntax.

• 1 Treat external input as untrusted until it is validated.
• 2 Avoid hardcoded secrets and never print sensitive values in examples or logs.
• 3 Use established libraries for authentication, encryption, parsing, and database access.

• 1 Exposing actuator endpoints publicly without security.
• 2 Not customizing health checks.
• 3 Ignoring metrics monitoring.
• 4 Leaving sensitive endpoints open.
• 5 Skipping the small working example before adding framework code.
• 6 Ignoring null, empty, duplicate, and boundary inputs.
• 7 Mixing business logic, input handling, and output formatting in one place.
• 8 Using broad error handling that hides the real failure.
• 9 Forgetting to test the behavior after refactoring.
• 10 Adding clever code that future maintainers will struggle to read.

• 1 Secure actuator endpoints.
• 2 Enable only required endpoints.
• 3 Use monitoring tools like Prometheus.
• 4 Customize health indicators.
• 5 Start with clear requirements and one minimal working example.
• 6 Use meaningful names that explain business intent.
• 7 Keep examples small enough to debug line by line.
• 8 Validate input at every trust boundary.
• 9 Handle errors explicitly and preserve useful context.
• 10 Prefer simple control flow over deeply nested logic.
• 11 Separate domain logic from I/O and framework code.
• 12 Write tests for normal, boundary, and failure cases.
• 13 Review security assumptions before production use.
• 14 Measure performance before optimizing.
• 15 Document non-obvious decisions close to the code or in project notes.
• 16 Use official documentation when behavior is version-specific.
• 17 Keep dependencies current and remove unused code.
• 18 Avoid hardcoded secrets, credentials, and environment-specific paths.
• 19 Log operational events without exposing sensitive data.
• 20 Design examples so learners can safely modify and rerun them.

• 1 Beginner: rewrite the example with different names and values.
• 2 Intermediate: add validation and handle one expected failure case.
• 3 Advanced: place Spring Boot Actuator Monitoring inside a small service-style design with tests.

• 1 Build a small Java console feature that demonstrates Spring Boot Actuator Monitoring.
• 2 Accept input, process it with the concept, print a clear result, and handle invalid input.
• 3 Add a README note explaining the design choice and two edge cases you tested.

• 1 If the program does not compile, check spelling, imports, braces, and file/class names first.
• 2 If output is unexpected, print intermediate values and verify each branch of the logic.
• 3 If the design feels complex, reduce it to the smallest working example and add pieces back one at a time.

• 1 Practice Spring Boot Actuator Monitoring with a second example from a business domain such as inventory, payroll, banking, or e-commerce.
• 2 Review related Java topics that cover data flow, error handling, testing, and clean design.
• 3 Compare your solution with official documentation and simplify anything you cannot explain clearly.