org.springframework.core.BridgeMethodResolver Maven / Gradle / Ivy
/*
* 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.core;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;
/**
* Helper for resolving synthetic {@link Method#isBridge bridge Methods} to the
* {@link Method} being bridged.
*
* Given a synthetic {@link Method#isBridge bridge Method} returns the {@link Method}
* being bridged. A bridge method may be created by the compiler when extending a
* parameterized type whose methods have parameterized arguments. During runtime
* invocation the bridge {@link Method} may be invoked and/or used via reflection.
* When attempting to locate annotations on {@link Method Methods}, it is wise to check
* for bridge {@link Method Methods} as appropriate and find the bridged {@link Method}.
*
*
See
* The Java Language Specification for more details on the use of bridge methods.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Phillip Webb
* @since 2.0
*/
public final class BridgeMethodResolver {
private BridgeMethodResolver() {
}
/**
* Find the original method for the supplied {@link Method bridge Method}.
*
It is safe to call this method passing in a non-bridge {@link Method} instance.
* In such a case, the supplied {@link Method} instance is returned directly to the caller.
* Callers are not required to check for bridging before calling this method.
* @param bridgeMethod the method to introspect
* @return the original method (either the bridged method or the passed-in method
* if no more specific one could be found)
*/
public static Method findBridgedMethod(Method bridgeMethod) {
if (!bridgeMethod.isBridge()) {
return bridgeMethod;
}
// Gather all methods with matching name and parameter size.
List candidateMethods = new ArrayList<>();
Method[] methods = ReflectionUtils.getAllDeclaredMethods(bridgeMethod.getDeclaringClass());
for (Method candidateMethod : methods) {
if (isBridgedCandidateFor(candidateMethod, bridgeMethod)) {
candidateMethods.add(candidateMethod);
}
}
// Now perform simple quick check.
if (candidateMethods.size() == 1) {
return candidateMethods.get(0);
}
// Search for candidate match.
Method bridgedMethod = searchCandidates(candidateMethods, bridgeMethod);
if (bridgedMethod != null) {
// Bridged method found...
return bridgedMethod;
}
else {
// A bridge method was passed in but we couldn't find the bridged method.
// Let's proceed with the passed-in method and hope for the best...
return bridgeMethod;
}
}
/**
* Returns {@code true} if the supplied '{@code candidateMethod}' can be
* consider a validate candidate for the {@link Method} that is {@link Method#isBridge() bridged}
* by the supplied {@link Method bridge Method}. This method performs inexpensive
* checks and can be used quickly filter for a set of possible matches.
*/
private static boolean isBridgedCandidateFor(Method candidateMethod, Method bridgeMethod) {
return (!candidateMethod.isBridge() && !candidateMethod.equals(bridgeMethod) &&
candidateMethod.getName().equals(bridgeMethod.getName()) &&
candidateMethod.getParameterCount() == bridgeMethod.getParameterCount());
}
/**
* Searches for the bridged method in the given candidates.
* @param candidateMethods the List of candidate Methods
* @param bridgeMethod the bridge method
* @return the bridged method, or {@code null} if none found
*/
@Nullable
private static Method searchCandidates(List candidateMethods, Method bridgeMethod) {
if (candidateMethods.isEmpty()) {
return null;
}
Method previousMethod = null;
boolean sameSig = true;
for (Method candidateMethod : candidateMethods) {
if (isBridgeMethodFor(bridgeMethod, candidateMethod, bridgeMethod.getDeclaringClass())) {
return candidateMethod;
}
else if (previousMethod != null) {
sameSig = sameSig &&
Arrays.equals(candidateMethod.getGenericParameterTypes(), previousMethod.getGenericParameterTypes());
}
previousMethod = candidateMethod;
}
return (sameSig ? candidateMethods.get(0) : null);
}
/**
* Determines whether or not the bridge {@link Method} is the bridge for the
* supplied candidate {@link Method}.
*/
static boolean isBridgeMethodFor(Method bridgeMethod, Method candidateMethod, Class declaringClass) {
if (isResolvedTypeMatch(candidateMethod, bridgeMethod, declaringClass)) {
return true;
}
Method method = findGenericDeclaration(bridgeMethod);
return (method != null && isResolvedTypeMatch(method, candidateMethod, declaringClass));
}
/**
* Returns {@code true} if the {@link Type} signature of both the supplied
* {@link Method#getGenericParameterTypes() generic Method} and concrete {@link Method}
* are equal after resolving all types against the declaringType, otherwise
* returns {@code false}.
*/
private static boolean isResolvedTypeMatch(Method genericMethod, Method candidateMethod, Class declaringClass) {
Type[] genericParameters = genericMethod.getGenericParameterTypes();
Class[] candidateParameters = candidateMethod.getParameterTypes();
if (genericParameters.length != candidateParameters.length) {
return false;
}
for (int i = 0; i < candidateParameters.length; i++) {
ResolvableType genericParameter = ResolvableType.forMethodParameter(genericMethod, i, declaringClass);
Class candidateParameter = candidateParameters[i];
if (candidateParameter.isArray()) {
// An array type: compare the component type.
if (!candidateParameter.getComponentType().equals(genericParameter.getComponentType().toClass())) {
return false;
}
}
// A non-array type: compare the type itself.
if (!candidateParameter.equals(genericParameter.toClass())) {
return false;
}
}
return true;
}
/**
* Searches for the generic {@link Method} declaration whose erased signature
* matches that of the supplied bridge method.
* @throws IllegalStateException if the generic declaration cannot be found
*/
@Nullable
private static Method findGenericDeclaration(Method bridgeMethod) {
// Search parent types for method that has same signature as bridge.
Class superclass = bridgeMethod.getDeclaringClass().getSuperclass();
while (superclass != null && Object.class != superclass) {
Method method = searchForMatch(superclass, bridgeMethod);
if (method != null && !method.isBridge()) {
return method;
}
superclass = superclass.getSuperclass();
}
Class[] interfaces = ClassUtils.getAllInterfacesForClass(bridgeMethod.getDeclaringClass());
return searchInterfaces(interfaces, bridgeMethod);
}
@Nullable
private static Method searchInterfaces(Class[] interfaces, Method bridgeMethod) {
for (Class ifc : interfaces) {
Method method = searchForMatch(ifc, bridgeMethod);
if (method != null && !method.isBridge()) {
return method;
}
else {
method = searchInterfaces(ifc.getInterfaces(), bridgeMethod);
if (method != null) {
return method;
}
}
}
return null;
}
/**
* If the supplied {@link Class} has a declared {@link Method} whose signature matches
* that of the supplied {@link Method}, then this matching {@link Method} is returned,
* otherwise {@code null} is returned.
*/
@Nullable
private static Method searchForMatch(Class type, Method bridgeMethod) {
try {
return type.getDeclaredMethod(bridgeMethod.getName(), bridgeMethod.getParameterTypes());
}
catch (NoSuchMethodException ex) {
return null;
}
}
/**
* Compare the signatures of the bridge method and the method which it bridges. If
* the parameter and return types are the same, it is a 'visibility' bridge method
* introduced in Java 6 to fix https://bugs.java.com/view_bug.do?bug_id=6342411.
* See also https://stas-blogspot.blogspot.com/2010/03/java-bridge-methods-explained.html
* @return whether signatures match as described
*/
public static boolean isVisibilityBridgeMethodPair(Method bridgeMethod, Method bridgedMethod) {
if (bridgeMethod == bridgedMethod) {
return true;
}
return (bridgeMethod.getReturnType().equals(bridgedMethod.getReturnType()) &&
Arrays.equals(bridgeMethod.getParameterTypes(), bridgedMethod.getParameterTypes()));
}
}