From 45939720f2b96cf2784e9c34a6ca0d627f8353b7 Mon Sep 17 00:00:00 2001
From: Stephane Nicoll <snicoll@vmware.com>
Date: Tue, 11 Oct 2022 09:37:02 +0200
Subject: [PATCH] Add native support for @ExceptionHandler

This commit makes sure that `@ExceptionHandler`-annotated methods can be
invoked via reflection in a native image. As most of the handling of
the parameter and the return type is shared with our generic
RequestMapping handling, the ReflectiveProcessor extends from it.

An `@ExceptionHandler`-annotated method can return a `ProblemDetail`. If
that's the case, reflection entries are contributed.

Closes gh-29297
---
 ...ControllerMappingReflectiveProcessor.java} | 57 ++++++++++---------
 .../web/bind/annotation/ExceptionHandler.java |  5 +-
 .../ExceptionHandlerReflectiveProcessor.java  | 40 +++++++++++++
 .../web/bind/annotation/RequestMapping.java   |  2 +-
 ...ollerMappingReflectiveProcessorTests.java} |  6 +-
 5 files changed, 78 insertions(+), 32 deletions(-)
 rename spring-web/src/main/java/org/springframework/web/bind/annotation/{RequestMappingReflectiveProcessor.java => ControllerMappingReflectiveProcessor.java} (59%)
 create mode 100644 spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandlerReflectiveProcessor.java
 rename spring-web/src/test/java/org/springframework/web/bind/annotation/{RequestMappingReflectiveProcessorTests.java => ControllerMappingReflectiveProcessorTests.java} (97%)

diff --git a/spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMappingReflectiveProcessor.java b/spring-web/src/main/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessor.java
similarity index 59%
rename from spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMappingReflectiveProcessor.java
rename to spring-web/src/main/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessor.java
index d2b03f12c1..878f3af049 100644
--- a/spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMappingReflectiveProcessor.java
+++ b/spring-web/src/main/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessor.java
@@ -29,11 +29,12 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.http.HttpEntity;
 import org.springframework.lang.Nullable;
+import org.springframework.stereotype.Controller;
 
 /**
- * {@link ReflectiveProcessor} implementation for {@link RequestMapping}
- * annotated types. On top of registering reflection hints for invoking
- * the annotated method, this implementation handles:
+ * {@link ReflectiveProcessor} implementation for {@link Controller} and
+ * controller-specific annotated methods. On top of registering reflection
+ * hints for invoking the annotated method, this implementation handles:
  * <ul>
  *     <li>Return types annotated with {@link ResponseBody}.</li>
  *     <li>Parameters annotated with {@link RequestBody}.</li>
@@ -44,7 +45,7 @@ import org.springframework.lang.Nullable;
  * @author Sebastien Deleuze
  * @since 6.0
  */
-class RequestMappingReflectiveProcessor implements ReflectiveProcessor {
+class ControllerMappingReflectiveProcessor implements ReflectiveProcessor {
 
 	private final BindingReflectionHintsRegistrar bindingRegistrar = new BindingReflectionHintsRegistrar();
 
@@ -58,45 +59,47 @@ class RequestMappingReflectiveProcessor implements ReflectiveProcessor {
 		}
 	}
 
+	protected final BindingReflectionHintsRegistrar getBindingRegistrar() {
+		return this.bindingRegistrar;
+	}
+
 	protected void registerTypeHints(ReflectionHints hints, Class<?> type) {
 		hints.registerType(type);
 	}
 
 	protected void registerMethodHints(ReflectionHints hints, Method method) {
-		hints.registerMethod(method, ExecutableMode.INVOKE);
-		registerParameterHints(hints, method);
-		registerReturnValueHints(hints, method);
-	}
-
-	protected void registerParameterHints(ReflectionHints hints, Method method) {
 		hints.registerMethod(method, ExecutableMode.INVOKE);
 		for (Parameter parameter : method.getParameters()) {
-			MethodParameter methodParameter = MethodParameter.forParameter(parameter);
-			if (methodParameter.hasParameterAnnotation(RequestBody.class) ||
-					methodParameter.hasParameterAnnotation(ModelAttribute.class)) {
-				this.bindingRegistrar.registerReflectionHints(hints, methodParameter.getGenericParameterType());
-			}
-			else if (HttpEntity.class.isAssignableFrom(methodParameter.getParameterType())) {
-				this.bindingRegistrar.registerReflectionHints(hints, getHttpEntityType(methodParameter));
-			}
+			registerParameterTypeHints(hints, MethodParameter.forParameter(parameter));
+		}
+		registerReturnTypeHints(hints, MethodParameter.forExecutable(method, -1));
+	}
+
+	protected void registerParameterTypeHints(ReflectionHints hints, MethodParameter methodParameter) {
+		if (methodParameter.hasParameterAnnotation(RequestBody.class) ||
+				methodParameter.hasParameterAnnotation(ModelAttribute.class)) {
+			this.bindingRegistrar.registerReflectionHints(hints, methodParameter.getGenericParameterType());
+		}
+		else if (HttpEntity.class.isAssignableFrom(methodParameter.getParameterType())) {
+			this.bindingRegistrar.registerReflectionHints(hints, getHttpEntityType(methodParameter));
 		}
 	}
 
-	protected void registerReturnValueHints(ReflectionHints hints, Method method) {
-		MethodParameter returnType = MethodParameter.forExecutable(method, -1);
-		if (AnnotatedElementUtils.hasAnnotation(returnType.getContainingClass(), ResponseBody.class) ||
-				returnType.hasMethodAnnotation(ResponseBody.class)) {
-			this.bindingRegistrar.registerReflectionHints(hints, returnType.getGenericParameterType());
+	protected void registerReturnTypeHints(ReflectionHints hints, MethodParameter returnTypeParameter) {
+		if (AnnotatedElementUtils.hasAnnotation(returnTypeParameter.getContainingClass(), ResponseBody.class) ||
+				returnTypeParameter.hasMethodAnnotation(ResponseBody.class)) {
+			this.bindingRegistrar.registerReflectionHints(hints, returnTypeParameter.getGenericParameterType());
 		}
-		else if (HttpEntity.class.isAssignableFrom(returnType.getParameterType())) {
-			this.bindingRegistrar.registerReflectionHints(hints, getHttpEntityType(returnType));
+		else if (HttpEntity.class.isAssignableFrom(returnTypeParameter.getParameterType())) {
+			this.bindingRegistrar.registerReflectionHints(hints, getHttpEntityType(returnTypeParameter));
 		}
 	}
 
 	@Nullable
-	protected Type getHttpEntityType(MethodParameter parameter) {
+	private Type getHttpEntityType(MethodParameter parameter) {
 		MethodParameter nestedParameter = parameter.nested();
-		return (nestedParameter.getNestedParameterType() == nestedParameter.getParameterType() ? null : nestedParameter.getNestedParameterType());
+		return (nestedParameter.getNestedParameterType() == nestedParameter.getParameterType()
+				? null : nestedParameter.getNestedParameterType());
 	}
 
 }
diff --git a/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandler.java b/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandler.java
index 4f0ee2ad78..bb80146627 100644
--- a/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandler.java
+++ b/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandler.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -22,6 +22,8 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.aot.hint.annotation.Reflective;
+
 /**
  * Annotation for handling exceptions in specific handler classes and/or
  * handler methods.
@@ -106,6 +108,7 @@ import java.lang.annotation.Target;
 @Target(ElementType.METHOD)
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
+@Reflective(ExceptionHandlerReflectiveProcessor.class)
 public @interface ExceptionHandler {
 
 	/**
diff --git a/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandlerReflectiveProcessor.java b/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandlerReflectiveProcessor.java
new file mode 100644
index 0000000000..448392ea75
--- /dev/null
+++ b/spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandlerReflectiveProcessor.java
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2022 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.web.bind.annotation;
+
+import org.springframework.aot.hint.ReflectionHints;
+import org.springframework.core.MethodParameter;
+import org.springframework.http.ProblemDetail;
+
+/**
+ * {@link ControllerMappingReflectiveProcessor} specific implementation that
+ * handles {@link ExceptionHandler @ExceptionHandler}-specific types.
+ *
+ * @author Stephane Nicoll
+ * @since 6.0
+ */
+class ExceptionHandlerReflectiveProcessor extends ControllerMappingReflectiveProcessor{
+
+	@Override
+	protected void registerReturnTypeHints(ReflectionHints hints, MethodParameter returnTypeParameter) {
+		Class<?> returnType = returnTypeParameter.getParameterType();
+		if (ProblemDetail.class.isAssignableFrom(returnType)) {
+			getBindingRegistrar().registerReflectionHints(hints, returnTypeParameter.getGenericParameterType());
+		}
+		super.registerReturnTypeHints(hints, returnTypeParameter);
+	}
+}
diff --git a/spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMapping.java b/spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMapping.java
index 65d7ceb668..9a677fa13f 100644
--- a/spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMapping.java
+++ b/spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMapping.java
@@ -73,7 +73,7 @@ import org.springframework.core.annotation.AliasFor;
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 @Mapping
-@Reflective(RequestMappingReflectiveProcessor.class)
+@Reflective(ControllerMappingReflectiveProcessor.class)
 public @interface RequestMapping {
 
 	/**
diff --git a/spring-web/src/test/java/org/springframework/web/bind/annotation/RequestMappingReflectiveProcessorTests.java b/spring-web/src/test/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessorTests.java
similarity index 97%
rename from spring-web/src/test/java/org/springframework/web/bind/annotation/RequestMappingReflectiveProcessorTests.java
rename to spring-web/src/test/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessorTests.java
index ce37f5ed69..8f68f9bc0d 100644
--- a/spring-web/src/test/java/org/springframework/web/bind/annotation/RequestMappingReflectiveProcessorTests.java
+++ b/spring-web/src/test/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessorTests.java
@@ -28,13 +28,13 @@ import org.springframework.http.HttpEntity;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link RequestMappingReflectiveProcessor}.
+ * Tests for {@link ControllerMappingReflectiveProcessor}.
  *
  * @author Sebastien Deleuze
  */
-public class RequestMappingReflectiveProcessorTests {
+public class ControllerMappingReflectiveProcessorTests {
 
-	private final RequestMappingReflectiveProcessor processor = new RequestMappingReflectiveProcessor();
+	private final ControllerMappingReflectiveProcessor processor = new ControllerMappingReflectiveProcessor();
 
 	private final ReflectionHints hints = new ReflectionHints();