/*
* Copyright 2002-2016 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.expression.spel.support;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.springframework.core.BridgeMethodResolver;
import org.springframework.core.MethodParameter;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.MethodExecutor;
import org.springframework.expression.MethodFilter;
import org.springframework.expression.MethodResolver;
import org.springframework.expression.TypeConverter;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
/**
* Reflection-based {@link MethodResolver} used by default in {@link StandardEvaluationContext}
* unless explicit method resolvers have been specified.
*
* @author Andy Clement
* @author Juergen Hoeller
* @author Chris Beams
* @since 3.0
* @see StandardEvaluationContext#addMethodResolver(MethodResolver)
*/
public class ReflectiveMethodResolver implements MethodResolver {
// Using distance will ensure a more accurate match is discovered,
// more closely following the Java rules.
private final boolean useDistance;
private Map<Class<?>, MethodFilter> filters;
public ReflectiveMethodResolver() {
this.useDistance = true;
}
/**
* This constructor allows the ReflectiveMethodResolver to be configured such that it
* will use a distance computation to check which is the better of two close matches
* (when there are multiple matches). Using the distance computation is intended to
* ensure matches are more closely representative of what a Java compiler would do
* when taking into account boxing/unboxing and whether the method candidates are
* declared to handle a supertype of the type (of the argument) being passed in.
* @param useDistance {@code true} if distance computation should be used when
* calculating matches; {@code false} otherwise
*/
public ReflectiveMethodResolver(boolean useDistance) {
this.useDistance = useDistance;
}
public void registerMethodFilter(Class<?> type, MethodFilter filter) {
if (this.filters == null) {
this.filters = new HashMap<>();
}
if (filter != null) {
this.filters.put(type, filter);
}
else {
this.filters.remove(type);
}
}
/**
* Locate a method on a type. There are three kinds of match that might occur:
* <ol>
* <li>an exact match where the types of the arguments match the types of the constructor
* <li>an in-exact match where the types we are looking for are subtypes of those defined on the constructor
* <li>a match where we are able to convert the arguments into those expected by the constructor,
* according to the registered type converter
* </ol>
*/
@Override
public MethodExecutor resolve(EvaluationContext context, Object targetObject, String name,
List<TypeDescriptor> argumentTypes) throws AccessException {
try {
TypeConverter typeConverter = context.getTypeConverter();
Class<?> type = (targetObject instanceof Class ? (Class<?>) targetObject : targetObject.getClass());
List<Method> methods = new ArrayList<>(getMethods(type, targetObject));
// If a filter is registered for this type, call it
MethodFilter filter = (this.filters != null ? this.filters.get(type) : null);
if (filter != null) {
List<Method> filtered = filter.filter(methods);
methods = (filtered instanceof ArrayList ? filtered : new ArrayList<>(filtered));
}
// Sort methods into a sensible order
if (methods.size() > 1) {
Collections.sort(methods, new Comparator<Method>() {
@Override
public int compare(Method m1, Method m2) {
int m1pl = m1.getParameterCount();
int m2pl = m2.getParameterCount();
// varargs methods go last
if (m1pl == m2pl) {
if (!m1.isVarArgs() && m2.isVarArgs()) {
return -1;
}
else if (m1.isVarArgs() && !m2.isVarArgs()) {
return 1;
}
else {
return 0;
}
}
return (m1pl < m2pl ? -1 : (m1pl > m2pl ? 1 : 0));
}
});
}
// Resolve any bridge methods
for (int i = 0; i < methods.size(); i++) {
methods.set(i, BridgeMethodResolver.findBridgedMethod(methods.get(i)));
}
// Remove duplicate methods (possible due to resolved bridge methods)
Set<Method> methodsToIterate = new LinkedHashSet<>(methods);
Method closeMatch = null;
int closeMatchDistance = Integer.MAX_VALUE;
Method matchRequiringConversion = null;
boolean multipleOptions = false;
for (Method method : methodsToIterate) {
if (method.getName().equals(name)) {
Class<?>[] paramTypes = method.getParameterTypes();
List<TypeDescriptor> paramDescriptors = new ArrayList<>(paramTypes.length);
for (int i = 0; i < paramTypes.length; i++) {
paramDescriptors.add(new TypeDescriptor(new MethodParameter(method, i)));
}
ReflectionHelper.ArgumentsMatchInfo matchInfo = null;
if (method.isVarArgs() && argumentTypes.size() >= (paramTypes.length - 1)) {
// *sigh* complicated
matchInfo = ReflectionHelper.compareArgumentsVarargs(paramDescriptors, argumentTypes, typeConverter);
}
else if (paramTypes.length == argumentTypes.size()) {
// Name and parameter number match, check the arguments
matchInfo = ReflectionHelper.compareArguments(paramDescriptors, argumentTypes, typeConverter);
}
if (matchInfo != null) {
if (matchInfo.isExactMatch()) {
return new ReflectiveMethodExecutor(method);
}
else if (matchInfo.isCloseMatch()) {
if (this.useDistance) {
int matchDistance = ReflectionHelper.getTypeDifferenceWeight(paramDescriptors, argumentTypes);
if (closeMatch == null || matchDistance < closeMatchDistance) {
// This is a better match...
closeMatch = method;
closeMatchDistance = matchDistance;
}
}
else {
// Take this as a close match if there isn't one already
if (closeMatch == null) {
closeMatch = method;
}
}
}
else if (matchInfo.isMatchRequiringConversion()) {
if (matchRequiringConversion != null) {
multipleOptions = true;
}
matchRequiringConversion = method;
}
}
}
}
if (closeMatch != null) {
return new ReflectiveMethodExecutor(closeMatch);
}
else if (matchRequiringConversion != null) {
if (multipleOptions) {
throw new SpelEvaluationException(SpelMessage.MULTIPLE_POSSIBLE_METHODS, name);
}
return new ReflectiveMethodExecutor(matchRequiringConversion);
}
else {
return null;
}
}
catch (EvaluationException ex) {
throw new AccessException("Failed to resolve method", ex);
}
}
private Collection<Method> getMethods(Class<?> type, Object targetObject) {
if (targetObject instanceof Class) {
Set<Method> result = new LinkedHashSet<>();
// Add these so that static methods are invocable on the type: e.g. Float.valueOf(..)
Method[] methods = getMethods(type);
for (Method method : methods) {
if (Modifier.isStatic(method.getModifiers())) {
result.add(method);
}
}
// Also expose methods from java.lang.Class itself
result.addAll(Arrays.asList(getMethods(Class.class)));
return result;
}
else {
return Arrays.asList(getMethods(type));
}
}
/**
* Return the set of methods for this type. The default implementation returns the
* result of {@link Class#getMethods()} for the given {@code type}, but subclasses
* may override in order to alter the results, e.g. specifying static methods
* declared elsewhere.
* @param type the class for which to return the methods
* @since 3.1.1
*/
protected Method[] getMethods(Class<?> type) {
return type.getMethods();
}
}