@RequestMapping without any attributes behaves as "default endpoint"

[anatoliy-balakirev]

Spring version: 5.1.5.RELEASE

In one of our micro services we've made a mistake and instead of writing something like this:

@RestController
@RequestMapping("/my/custom/controller")
public class MyController {

// GET and POST methods mapped to `/my/custom/controller` endpoint

Created this:

@RestController("/my/custom/controller")
public class MyController {

Everything worked fine, all our requests were handled but then at some point we realised that all requests, even for non-existing endpoints, are mapped to that controller. So this:

http://localhost:8080/whatever

Was getting into our controller by default:

2019-03-07 16:47:28.014 DEBUG 83179 --- [nio-8080-exec-3] o.s.web.servlet.DispatcherServlet        : GET "/whatever", parameters={}
2019-03-07 16:47:28.016 DEBUG 83179 --- [nio-8080-exec-3] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to public void com.example.demo.MyController.doSomething()
Got to my custom controller 1
2019-03-07 16:47:28.017 DEBUG 83179 --- [nio-8080-exec-3] m.m.a.RequestResponseBodyMethodProcessor : Using 'application/json', given [*/*] and supported [application/json, application/*+json, application/json, application/*+json]
2019-03-07 16:47:28.017 DEBUG 83179 --- [nio-8080-exec-3] m.m.a.RequestResponseBodyMethodProcessor : Nothing to write: null body
2019-03-07 16:47:28.017 DEBUG 83179 --- [nio-8080-exec-3] o.s.web.servlet.DispatcherServlet        : Completed 200 OK

With that config in place, I would expect to get 404 for both: /whatever and /my/custom/controller requests, because in fact there is no mapping for /my/custom/controller in my app (there is a bean with that name instead).

Here is a whole controller's code, no other config is required to reproduce this, just standard spring boot app with this single controller:

package com.example.demo;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController("/my/custom/controller")
public class MyController {

    @GetMapping
    public void doSomething() {
        System.out.println("Got to my custom controller 1");
    }

    @PutMapping
    public void doSomethingElse() {
        System.out.println("Got to my custom controller 2");
    }

}

[sbrannen]

Please note that Spring MVC supports mapping from bean names (that begin with a forward slash /) to controllers.

See the javadoc for BeanNameUrlHandlerMapping for details.

Thus, in your use case, when "/my/custom/controller" is configured as the bean name for the controller (i.e., via the value attribute in @RestController), that path is used by BeanNameUrlHandlerMapping to register a handler mapping automatically.

So that explains why you do not get a 404 for requests to "/my/custom/controller".

Regarding the /whatever requests, is there a similarity between the real value for "whatever" and the actual bean name of the REST controller?

[anatoliy-balakirev]

Nope, there is no similarity. I'm literally sending that whatever in the request. In fact any request is getting mapped to that controller. Just tried this:
http://localhost:8080/some_non_existing_endpoint
And here are logs:

2019-03-07 17:19:09.198  INFO 83733 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-03-07 17:19:09.198  INFO 83733 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2019-03-07 17:19:09.198 DEBUG 83733 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Detected StandardServletMultipartResolver
2019-03-07 17:19:09.211 DEBUG 83733 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : enableLoggingRequestDetails='false': request parameters and headers will be masked to prevent unsafe logging of potentially sensitive data
2019-03-07 17:19:09.212  INFO 83733 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed initialization in 14 ms
2019-03-07 17:19:09.222 DEBUG 83733 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : GET "/some_non_existing_endpoint", parameters={}
2019-03-07 17:19:09.230 DEBUG 83733 --- [nio-8080-exec-2] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to public void com.example.demo.MyController.doSomething()
Got to my custom controller 1
2019-03-07 17:19:09.263 DEBUG 83733 --- [nio-8080-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Using 'application/json', given [*/*] and supported [application/json, application/*+json, application/json, application/*+json]
2019-03-07 17:19:09.264 DEBUG 83733 --- [nio-8080-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Nothing to write: null body
2019-03-07 17:19:09.264 DEBUG 83733 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed 200 OK

More readable extraction from there:

GET "/some_non_existing_endpoint", parameters={}
Mapped to public void com.example.demo.MyController.doSomething()

This controller class is the only bean I have in my freshly created spring boot app.

[sbrannen]

@anatoliy-balakirev, thanks for the feedback.

This controller class is the only bean I have in my freshly created spring boot app.

Good to know.

Based on some quick experimentation, you should experience the same behavior if you simply annotate your controller class with @RestController (i.e., without specifying any bean name).

[anatoliy-balakirev]

Here is a sample project: https://github.com/anatoliy-balakirev/rest-controller-mapping