/*
* Copyright 2002-2008 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
*
* http://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.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
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.
*
* <p>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}.
*
* <p>See <a href="http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.12.4.5">
* The Java Language Specification</a> for more details on the use of bridge methods.
*
* <p>Only usable on JDK 1.5 and higher. Use an appropriate {@link JdkVersion}
* check before calling this class if a fallback for JDK 1.4 is desirable.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
* @see JdkVersion
*/
public abstract class BridgeMethodResolver {
/**
* Find the original method for the supplied {@link Method bridge Method}.
* <p>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 <strong>not</strong> required to check for bridging before calling this method.
* @throws IllegalStateException if no bridged {@link Method} can be found
*/
public static Method findBridgedMethod(Method bridgeMethod) {
if (bridgeMethod == null || !bridgeMethod.isBridge()) {
return bridgeMethod;
}
// Gather all methods with matching name and parameter size.
List candidateMethods = new ArrayList();
Method[] methods = ReflectionUtils.getAllDeclaredMethods(bridgeMethod.getDeclaringClass());
for (int i = 0; i < methods.length; i++) {
Method candidateMethod = methods[i];
if (isBridgedCandidateFor(candidateMethod, bridgeMethod)) {
candidateMethods.add(candidateMethod);
}
}
Method result;
// Now perform simple quick checks.
if (candidateMethods.size() == 1) {
result = (Method) candidateMethods.get(0);
}
else {
result = searchCandidates(candidateMethods, bridgeMethod);
}
if (result == null) {
throw new IllegalStateException(
"Unable to locate bridged method for bridge method '" + bridgeMethod + "'");
}
return result;
}
/**
* 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</code> if none found
*/
private static Method searchCandidates(List candidateMethods, Method bridgeMethod) {
Map typeParameterMap = GenericTypeResolver.getTypeVariableMap(bridgeMethod.getDeclaringClass());
for (int i = 0; i < candidateMethods.size(); i++) {
Method candidateMethod = (Method) candidateMethods.get(i);
if (isBridgeMethodFor(bridgeMethod, candidateMethod, typeParameterMap)) {
return candidateMethod;
}
}
return null;
}
/**
* Returns <code>true</code> if the supplied '<code>candidateMethod</code>' 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.getParameterTypes().length == bridgeMethod.getParameterTypes().length);
}
/**
* Determines whether or not the bridge {@link Method} is the bridge for the
* supplied candidate {@link Method}.
*/
static boolean isBridgeMethodFor(Method bridgeMethod, Method candidateMethod, Map typeVariableMap) {
if (isResolvedTypeMatch(candidateMethod, bridgeMethod, typeVariableMap)) {
return true;
}
Method method = findGenericDeclaration(bridgeMethod);
return (method != null && isResolvedTypeMatch(method, candidateMethod, typeVariableMap));
}
/**
* 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
*/
private static Method findGenericDeclaration(Method bridgeMethod) {
// Search parent types for method that has same signature as bridge.
Class superclass = bridgeMethod.getDeclaringClass().getSuperclass();
while (!Object.class.equals(superclass)) {
Method method = searchForMatch(superclass, bridgeMethod);
if (method != null && !method.isBridge()) {
return method;
}
superclass = superclass.getSuperclass();
}
// Search interfaces.
Class[] interfaces = ClassUtils.getAllInterfacesForClass(bridgeMethod.getDeclaringClass());
for (int i = 0; i < interfaces.length; i++) {
Class anInterface = interfaces[i];
Method method = searchForMatch(anInterface, bridgeMethod);
if (method != null && !method.isBridge()) {
return method;
}
}
return null;
}
/**
* Returns <code>true</code> if the {@link Type} signature of both the supplied
* {@link Method#getGenericParameterTypes() generic Method} and concrete {@link Method}
* are equal after resolving all {@link TypeVariable TypeVariables} using the supplied
* TypeVariable Map, otherwise returns <code>false</code>.
*/
private static boolean isResolvedTypeMatch(Method genericMethod, Method candidateMethod, Map typeVariableMap) {
Type[] genericParameters = genericMethod.getGenericParameterTypes();
Class[] candidateParameters = candidateMethod.getParameterTypes();
if (genericParameters.length != candidateParameters.length) {
return false;
}
for (int i = 0; i < genericParameters.length; i++) {
Type genericParameter = genericParameters[i];
Class candidateParameter = candidateParameters[i];
if (candidateParameter.isArray()) {
// An array type: compare the component type.
Type rawType = GenericTypeResolver.getRawType(genericParameter, typeVariableMap);
if (rawType instanceof GenericArrayType) {
if (!candidateParameter.getComponentType().equals(
GenericTypeResolver.resolveType(((GenericArrayType) rawType).getGenericComponentType(), typeVariableMap))) {
return false;
}
break;
}
}
// A non-array type: compare the type itself.
if (!candidateParameter.equals(GenericTypeResolver.resolveType(genericParameter, typeVariableMap))) {
return false;
}
}
return true;
}
/**
* 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</code> is returned.
*/
private static Method searchForMatch(Class type, Method bridgeMethod) {
return ReflectionUtils.findMethod(type, bridgeMethod.getName(), bridgeMethod.getParameterTypes());
}
}