Avoid mismatch between cached top-level versus nested parameter type

Issue: SPR-13755

spring-core/src/main/java/org/springframework/core/GenericTypeResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -51,28 +51,28 @@ public abstract class GenericTypeResolver {
 
 	/**
 	 * Determine the target type for the given parameter specification.
-	 * @param methodParam the method parameter specification
+	 * @param methodParameter the method parameter specification
 	 * @return the corresponding generic parameter type
 	 * @deprecated as of Spring 4.0, use {@link MethodParameter#getGenericParameterType()}
 	 */
 	@Deprecated
-	public static Type getTargetType(MethodParameter methodParam) {
-		Assert.notNull(methodParam, "MethodParameter must not be null");
-		return methodParam.getGenericParameterType();
+	public static Type getTargetType(MethodParameter methodParameter) {
+		Assert.notNull(methodParameter, "MethodParameter must not be null");
+		return methodParameter.getGenericParameterType();
 	}
 
 	/**
 	 * Determine the target type for the given generic parameter type.
-	 * @param methodParam the method parameter specification
-	 * @param clazz the class to resolve type variables against
+	 * @param methodParameter the method parameter specification
+	 * @param implementationClass the class to resolve type variables against
 	 * @return the corresponding generic parameter or return type
 	 */
-	public static Class<?> resolveParameterType(MethodParameter methodParam, Class<?> clazz) {
-		Assert.notNull(methodParam, "MethodParameter must not be null");
-		Assert.notNull(clazz, "Class must not be null");
-		methodParam.setContainingClass(clazz);
-		methodParam.setParameterType(ResolvableType.forMethodParameter(methodParam).resolve());
-		return methodParam.getParameterType();
+	public static Class<?> resolveParameterType(MethodParameter methodParameter, Class<?> implementationClass) {
+		Assert.notNull(methodParameter, "MethodParameter must not be null");
+		Assert.notNull(implementationClass, "Class must not be null");
+		methodParameter.setContainingClass(implementationClass);
+		ResolvableType.resolveMethodParameter(methodParameter);
+		return methodParameter.getParameterType();
 	}
 
 	/**

spring-core/src/main/java/org/springframework/core/ResolvableType.java

@@ -1219,11 +1219,11 @@ public class ResolvableType implements Serializable {
 	 */
 	public static ResolvableType forMethodParameter(MethodParameter methodParameter, ResolvableType implementationType) {
 		Assert.notNull(methodParameter, "MethodParameter must not be null");
-		implementationType = (implementationType == null ? forType(methodParameter.getContainingClass()) : implementationType);
+		implementationType = (implementationType != null ? implementationType :
+				forType(methodParameter.getContainingClass()));
 		ResolvableType owner = implementationType.as(methodParameter.getDeclaringClass());
-		return forType(null, new MethodParameterTypeProvider(methodParameter),
-				owner.asVariableResolver()).getNested(methodParameter.getNestingLevel(),
-				methodParameter.typeIndexesPerLevel);
+		return forType(null, new MethodParameterTypeProvider(methodParameter), owner.asVariableResolver()).
+				getNested(methodParameter.getNestingLevel(), methodParameter.typeIndexesPerLevel);
 	}
 
 	/**
@@ -1241,13 +1241,26 @@ public class ResolvableType implements Serializable {
 				getNested(methodParameter.getNestingLevel(), methodParameter.typeIndexesPerLevel);
 	}
 
+	/**
+	 * Resolve the top-level parameter type of the given {@code MethodParameter}.
+	 * @param methodParameter the method parameter to resolve
+	 * @since 4.1.9
+	 * @see MethodParameter#setParameterType
+	 */
+	static void resolveMethodParameter(MethodParameter methodParameter) {
+		Assert.notNull(methodParameter, "MethodParameter must not be null");
+		ResolvableType owner = forType(methodParameter.getContainingClass()).as(methodParameter.getDeclaringClass());
+		methodParameter.setParameterType(
+				forType(null, new MethodParameterTypeProvider(methodParameter), owner.asVariableResolver()).resolve());
+	}
+
 	/**
 	 * Return a {@link ResolvableType} as a array of the specified {@code componentType}.
 	 * @param componentType the component type
 	 * @return a {@link ResolvableType} as an array of the specified component type
 	 */
 	public static ResolvableType forArrayComponent(ResolvableType componentType) {
-		Assert.notNull(componentType, "componentType must not be null");
+		Assert.notNull(componentType, "Component type must not be null");
 		Class<?> arrayClass = Array.newInstance(componentType.resolve(), 0).getClass();
 		return new ResolvableType(arrayClass, null, null, componentType);
 	}