Ignore scoped proxy targets for @ControllerAdvice beans

Prior to this commit, methods in a @ControllerAdvice bean were
registered and invoked twice if the advice was a scoped bean (e.g.,
request or session scoped). In other words, both the proxy bean and the
target bean were wrapped in ControllerAdviceBean instances.

This commit fixes this bug by modifying the findAnnotatedBeans() method
in ControllerAdviceBean so that it filters out targets of scoped
proxies.

Closes gh-24017

spring-test/src/test/java/org/springframework/test/web/servlet/samples/spr/ControllerAdviceIntegrationTests.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright 2002-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.test.web.servlet.samples.spr;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.stereotype.Controller;
+import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.ModelAttribute;
+import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.context.annotation.RequestScope;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.forwardedUrl;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+import static org.springframework.test.web.servlet.setup.MockMvcBuilders.webAppContextSetup;
+
+/**
+ * Integration tests for {@link ControllerAdvice @ControllerAdvice}.
+ *
+ * <p>Introduced in conjunction with
+ * <a href="https://github.com/spring-projects/spring-framework/issues/24017">gh-24017</a>.
+ *
+ * @author Sam Brannen
+ * @since 5.1.12
+ */
+@SpringJUnitWebConfig
+class ControllerAdviceIntegrationTests {
+
+	MockMvc mockMvc;
+
+	@BeforeEach
+	void setUpMockMvc(WebApplicationContext wac) {
+		this.mockMvc = webAppContextSetup(wac).build();
+	}
+
+	@Test
+	void controllerAdviceIsAppliedOnlyOnce() throws Exception {
+		assertThat(SingletonControllerAdvice.counter).hasValue(0);
+		assertThat(RequestScopedControllerAdvice.counter).hasValue(0);
+
+		this.mockMvc.perform(get("/test"))//
+				.andExpect(status().isOk())//
+				.andExpect(forwardedUrl("singleton:1;request-scoped:1"));
+
+		assertThat(SingletonControllerAdvice.counter).hasValue(1);
+		assertThat(RequestScopedControllerAdvice.counter).hasValue(1);
+	}
+
+	@Configuration
+	@EnableWebMvc
+	static class Config {
+
+		@Bean
+		TestController testController() {
+			return new TestController();
+		}
+
+		@Bean
+		SingletonControllerAdvice singletonControllerAdvice() {
+			return new SingletonControllerAdvice();
+		}
+
+		@Bean
+		@RequestScope
+		RequestScopedControllerAdvice requestScopedControllerAdvice() {
+			return new RequestScopedControllerAdvice();
+		}
+	}
+
+	@ControllerAdvice
+	static class SingletonControllerAdvice {
+
+		static final AtomicInteger counter = new AtomicInteger();
+
+		@ModelAttribute
+		void initModel(Model model) {
+			model.addAttribute("singleton", counter.incrementAndGet());
+		}
+	}
+
+	@ControllerAdvice
+	static class RequestScopedControllerAdvice {
+
+		static final AtomicInteger counter = new AtomicInteger();
+
+		@ModelAttribute
+		void initModel(Model model) {
+			model.addAttribute("request-scoped", counter.incrementAndGet());
+		}
+	}
+
+	@Controller
+	static class TestController {
+
+		@GetMapping("/test")
+		String get(Model model) {
+			return "singleton:" + model.getAttribute("singleton") + ";request-scoped:"
+					+ model.getAttribute("request-scoped");
+		}
+	}
+
+}