How to implement custom Health indicators in Spring Boot

Spring Boot provides the following HealthIndicator implementations out-of-the-box. They are auto-configured by default:

• CassandraHealthIndicator
• DiskSpaceHealthIndicator
• DataSourceHealthIndicator
• ElasticsearchHealthIndicator
• JmsHealthIndicator
• MailHealthIndicator
• MongoHealthIndicator
• RabbitHealthIndicator
• RedisHealthIndicator
• SolrHealthIndicator

package com.example.samplewebapp;

import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.boot.json.JsonParser;
import org.springframework.boot.json.JsonParserFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestTemplate;
import java.util.Date;
import java.util.Map;

@Component
public class RestHealthIndicator implements HealthIndicator {
  @Override
  public Health health() {
    RestTemplate restTemplate = new RestTemplate();
    String url = "https://jsonplaceholder.typicode.com/todos/1";
    try {
      String resp = restTemplate.getForObject(url, String.class);
      System.out.println("-------------->" + resp);
      JsonParser springParser = JsonParserFactory.getJsonParser();
      Map<String, Object> map = springParser.parseMap(resp);
      if ("delectus aut autem".equalsIgnoreCase((String) map.get("title"))) {
        return Health.up().build();
      } else {
        return Health.down()
            .withDetail("ping_url", url)
            .withDetail("ping_time", new Date())
            .build();
      }
    } catch (RestClientException e) {
      return Health.down(e).withDetail("ping_url", url).withDetail("ping_time", new Date()).build();
    }
  }
}

If we try to reach the Internet URL https://jsonplaceholder.typicode.com/todos/1 the following code JSON is returned:

{   "userId": 1,   "id": 1,   "title": "delectus aut autem",   "completed": false }

We have implemented the same logic in our Health indicator so that if you try to reach the “/actuator/health” URL, the health() callback is performed. This is a simple way to check if you are connected to Internet.

$ curl http://localhost:8080/actuator/health {"status":"UP"}