ControllerAdviceBean.findAnnotatedBeans() finds proxies as well as their target beans, resulting in double registration

[sbrannen]

Overview

While implementing a fix for the regression raised in #23985, it became apparent that methods in a @ControllerAdvice bean end up being registered and invoked twice if the advice is a scoped bean (e.g., request or session scoped). In other words, both the proxy bean and the target bean are wrapped in ControllerAdviceBean instances.

The reason this happens is that ControllerAdviceBean.findAnnotatedBeans() finds all beans in the ApplicationContext that are annotated with @ControllerAdvice.

Deliverables

• Ensure that the list returned by ControllerAdviceBean.findAnnotatedBeans() does not contain target beans for scoped proxies.

[sbrannen]

The following failing test case demonstrates the undesired behavior.

@SpringJUnitWebConfig
class RequestScopedControllerAdviceIntegrationTests {

	MockMvc mockMvc;

	@BeforeEach
	void setUpMockMvc(WebApplicationContext wac) throws Exception {
		this.mockMvc = webAppContextSetup(wac).build();
	}

	@Test
	void test() throws Exception {
		this.mockMvc.perform(get("/test"))//
				.andExpect(status().isOk())//
				.andExpect(forwardedUrl("count: 1"));

	}

	@Configuration
	@EnableWebMvc
	static class Config {

		@Bean
		TestController testController() {
			return new TestController();
		}

		@Bean
		@RequestScope
		RequestScopedControllerAdvice requestScopedControllerAdvice() {
			return new RequestScopedControllerAdvice();
		}
	}

	@ControllerAdvice
	static class RequestScopedControllerAdvice {

		static final AtomicInteger counter = new AtomicInteger();

		@ModelAttribute
		public void initModel(Model model) {
			model.addAttribute("count", counter.incrementAndGet());
		}
	}

	@Controller
	static class TestController {

		@GetMapping("/test")
		String get(Model model) {
			return "count: " + model.getAttribute("count");
		}
	}

}