Spring boot actuator - Implement custom metrics

Question

I would like to implement custom metric or statistics to my spring boot rest web service using actuator but i am not able to find simple tutorials. For example:

• how to show how many times a certain controller was called and what exact parameter field was filled?
• how can i create a metric that when its URL is called, it runs certain query and shows back a json with some result

Answer 1

For point two the solution is to create an endpoint class (it can be or not a rest controller class). For example:

@Component
@RestControllerEndpoint(id = "pfm-statistics")
public class StatisticsEndpoint {
  @GetMapping(value = "/", produces = "application/vnd.openxmlformats- 
     officedocument.spreadsheetml.sheet")
  @ResponseBody
  public byte[] generateStatisticsAsExcel() {
 ...

Note that the ID is the path to be called from URL. We can create a simple endpoint too and just return a string if we want. In this case instead of @RestControllerEndpoint annotation we can use @Endpoint, as a side note, the id should always contain dash