/*
* Copyright 2002-2012 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.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
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;
import org.springframework.util.CollectionUtils;
/**
* 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 {
private static Method[] NO_METHODS = new Method[0];
private Map<Class<?>, MethodFilter> filters = null;
// Using distance will ensure a more accurate match is discovered,
// more closely following the Java rules.
private boolean useDistance = false;
public ReflectiveMethodResolver() {
}
/**
* This constructors 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 true if distance computation should be used when calculating matches
*/
public ReflectiveMethodResolver(boolean useDistance) {
this.useDistance = useDistance;
}
/**
* 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>
*/
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());
Method[] methods = 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> methodsForFiltering = new ArrayList<Method>();
for (Method method: methods) {
methodsForFiltering.add(method);
}
List<Method> methodsFiltered = filter.filter(methodsForFiltering);
if (CollectionUtils.isEmpty(methodsFiltered)) {
methods = NO_METHODS;
}
else {
methods = methodsFiltered.toArray(new Method[methodsFiltered.size()]);
}
}
Arrays.sort(methods, new Comparator<Method>() {
public int compare(Method m1, Method m2) {
int m1pl = m1.getParameterTypes().length;
int m2pl = m2.getParameterTypes().length;
return (new Integer(m1pl)).compareTo(m2pl);
}
});
Method closeMatch = null;
int closeMatchDistance = Integer.MAX_VALUE;
int[] argsToConvert = null;
Method matchRequiringConversion = null;
boolean multipleOptions = false;
for (Method method : methods) {
if (method.isBridge()) {
continue;
}
if (method.getName().equals(name)) {
Class<?>[] paramTypes = method.getParameterTypes();
List<TypeDescriptor> paramDescriptors = new ArrayList<TypeDescriptor>(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.kind == ReflectionHelper.ArgsMatchKind.EXACT) {
return new ReflectiveMethodExecutor(method, null);
}
else if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.CLOSE) {
if (!useDistance) {
closeMatch = method;
} else {
int matchDistance = ReflectionHelper.getTypeDifferenceWeight(paramDescriptors, argumentTypes);
if (matchDistance<closeMatchDistance) {
// this is a better match
closeMatchDistance = matchDistance;
closeMatch = method;
}
}
}
else if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.REQUIRES_CONVERSION) {
if (matchRequiringConversion != null) {
multipleOptions = true;
}
argsToConvert = matchInfo.argsRequiringConversion;
matchRequiringConversion = method;
}
}
}
}
if (closeMatch != null) {
return new ReflectiveMethodExecutor(closeMatch, null);
}
else if (matchRequiringConversion != null) {
if (multipleOptions) {
throw new SpelEvaluationException(SpelMessage.MULTIPLE_POSSIBLE_METHODS, name);
}
return new ReflectiveMethodExecutor(matchRequiringConversion, argsToConvert);
}
else {
return null;
}
}
catch (EvaluationException ex) {
throw new AccessException("Failed to resolve method", ex);
}
}
public void registerMethodFilter(Class<?> type, MethodFilter filter) {
if (this.filters == null) {
this.filters = new HashMap<Class<?>, MethodFilter>();
}
if (filter == null) {
this.filters.remove(type);
}
else {
this.filters.put(type,filter);
}
}
private Method[] getMethods(Class<?> type, Object targetObject) {
if(targetObject instanceof Class) {
Set<Method> methods = new HashSet<Method>();
methods.addAll(Arrays.asList(getMethods(type)));
methods.addAll(Arrays.asList(getMethods(targetObject.getClass())));
return methods.toArray(new Method[methods.size()]);
}
return getMethods(type);
}
/**
* Return the set of methods for this type. The default implementation returns the
* result of 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();
}
}