Write operation for actuator endpoint is not working with bean classes

[DanielLupu]

Spring Boot version: 2.0.3.RELEASE

The Spring Boot example for using @WriteOperation can be found at "Endpoint infrastructure" section
This example is working OK because JSON body is passed as a parameter with string value: { "configuredLevel": "WARN" } and LogLevel is an enum.

Unfortunately, if you will try to pass a bean class included in body for a HTTP POST request then it will fail with 400 - bad request. You can take a look at this example which is not working:
http://www.baeldung.com/spring-boot-actuators, 4.7. "Creating a Custom Endpoint" section

Using curl command:

$ curl -X POST http://localhost:8080/actuator/features/payment -H "Content-Type: application/json" -d '{"enabled":  true}'
response: 
{"timestamp":"2018-07-23T09:57:57.922+0000","status":400,"error":"Bad Request","message":"Missing parameters: feature","path":"/actuator/features/payment"}

It indicates a missing feature parameter. Even though this feature parameter is added:

$ curl -X POST http://localhost:8080/actuator/features/payment -H "Content-Type: application/json" -d '{"feature": {"enabled":true}}'
response:
"Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of java.lang.String out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException"
Feature bean class is not interpreted because Jackson is expecting a string instead of a bean class.

After debugging Jackson and Spring sources I found that the problem appears at startup, because RequestMappingHandlerMapping.isHandler() knows to create handler for identifying bean classes from endpoint methods only for Controller and RequestMapping. According to 50.8 "Implementing Custom Endpoints" section Endpoint and WebEndpoint are exposed over HTTP.
Therefore, both classes should be added in isHandler() method to create a handler for parsing bean classes.

[philwebb]

Can you please share the sample project you've been using that shows the error. I wonder if perhaps you've accidentally added @Controller or @RestController to your endpoint>

The RequestMappingHandlerMapping.isHandler() method isn't used by the actuator code. See the org.springframework.boot.actuate.endpoint.web.servlet.ControllerEndpointHandlerMapping class for details.

[DanielLupu]

There are no accidental Controller or RestController annotations. RequestMappingHandlerMapping is not an abstract class, so in our case it is instantiated without a need of ControllerEndpointHandlerMapping

Below you can find the stack trace:

[snicoll]

@DanielLupu thank you but that's not what we had in mind. Please share a sample that we can clone/download and run ourselves.

[DanielLupu]

Or simple just use the attached sources:
spring-boot-custom-endpoint.zip

[snicoll]

Thanks for the sample. This is working as advertized:

1. As you're working with the endpoint abstraction, we want to make sure that such endpoint can be invoked via JMX. Declaring such type will not allow that
2. It looks like you expect the JSON body to be serialized back to Feature. What should happen if you add a third parameter?

If you want to end up with such higher-level method signature, I am not sure @Endpoint is the right fit for you (considering the JMX use case).