/*
* Copyright 2002-2010 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.Constructor;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import org.springframework.core.MethodParameter;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
import org.springframework.expression.ConstructorExecutor;
import org.springframework.expression.ConstructorResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypeConverter;
/**
* A constructor resolver that uses reflection to locate the constructor that should be invoked
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public class ReflectiveConstructorResolver implements ConstructorResolver {
/**
* Locate a constructor on the 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 ConstructorExecutor resolve(EvaluationContext context, String typename, List<TypeDescriptor> argumentTypes)
throws AccessException {
try {
TypeConverter typeConverter = context.getTypeConverter();
Class<?> type = context.getTypeLocator().findType(typename);
Constructor[] ctors = type.getConstructors();
Arrays.sort(ctors, new Comparator<Constructor>() {
public int compare(Constructor c1, Constructor c2) {
int c1pl = c1.getParameterTypes().length;
int c2pl = c2.getParameterTypes().length;
return (new Integer(c1pl)).compareTo(c2pl);
}
});
Constructor closeMatch = null;
int[] argsToConvert = null;
Constructor matchRequiringConversion = null;
for (Constructor ctor : ctors) {
Class[] paramTypes = ctor.getParameterTypes();
List<TypeDescriptor> paramDescriptors = new ArrayList<TypeDescriptor>(paramTypes.length);
for (int i = 0; i < paramTypes.length; i++) {
paramDescriptors.add(new TypeDescriptor(new MethodParameter(ctor, i)));
}
ReflectionHelper.ArgumentsMatchInfo matchInfo = null;
if (ctor.isVarArgs() && argumentTypes.size() >= (paramTypes.length - 1)) {
// *sigh* complicated
// Basically.. we have to have all parameters match up until the varargs one, then the rest of what is
// being provided should be
// the same type whilst the final argument to the method must be an array of that (oh, how easy...not) -
// or the final parameter
// we are supplied does match exactly (it is an array already).
matchInfo = ReflectionHelper.compareArgumentsVarargs(paramDescriptors, argumentTypes, typeConverter);
}
else if (paramTypes.length == argumentTypes.size()) {
// worth a closer look
matchInfo = ReflectionHelper.compareArguments(paramDescriptors, argumentTypes, typeConverter);
}
if (matchInfo != null) {
if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.EXACT) {
return new ReflectiveConstructorExecutor(ctor, null);
}
else if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.CLOSE) {
closeMatch = ctor;
}
else if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.REQUIRES_CONVERSION) {
argsToConvert = matchInfo.argsRequiringConversion;
matchRequiringConversion = ctor;
}
}
}
if (closeMatch != null) {
return new ReflectiveConstructorExecutor(closeMatch, null);
}
else if (matchRequiringConversion != null) {
return new ReflectiveConstructorExecutor(matchRequiringConversion, argsToConvert);
}
else {
return null;
}
}
catch (EvaluationException ex) {
throw new AccessException("Failed to resolve constructor", ex);
}
}
}
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