/*
* 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.ast;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import org.springframework.expression.PropertyAccessor;
/**
* Utilities methods for use in the Ast classes.
*
* @author Andy Clement
* @since 3.0.2
*/
public abstract class AstUtils {
/**
* Determines the set of property resolvers that should be used to try and access a
* property on the specified target type. The resolvers are considered to be in an
* ordered list, however in the returned list any that are exact matches for the input
* target type (as opposed to 'general' resolvers that could work for any type) are
* placed at the start of the list. In addition, there are specific resolvers that
* exactly name the class in question and resolvers that name a specific class but it
* is a supertype of the class we have. These are put at the end of the specific resolvers
* set and will be tried after exactly matching accessors but before generic accessors.
* @param targetType the type upon which property access is being attempted
* @return a list of resolvers that should be tried in order to access the property
*/
public static List<PropertyAccessor> getPropertyAccessorsToTry(
Class<?> targetType, List<PropertyAccessor> propertyAccessors) {
List<PropertyAccessor> specificAccessors = new ArrayList<>();
List<PropertyAccessor> generalAccessors = new ArrayList<>();
for (PropertyAccessor resolver : propertyAccessors) {
Class<?>[] targets = resolver.getSpecificTargetClasses();
if (targets == null) { // generic resolver that says it can be used for any type
generalAccessors.add(resolver);
}
else {
if (targetType != null) {
int pos = 0;
for (Class<?> clazz : targets) {
if (clazz == targetType) { // put exact matches on the front to be tried first?
specificAccessors.add(pos++, resolver);
}
else if (clazz.isAssignableFrom(targetType)) { // put supertype matches at the end of the
// specificAccessor list
generalAccessors.add(resolver);
}
}
}
}
}
List<PropertyAccessor> resolvers = new LinkedList<>();
resolvers.addAll(specificAccessors);
resolvers.addAll(generalAccessors);
return resolvers;
}
}