1 /*
2 * Copyright 2002-2014 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.springframework.expression.spel.ast;
18
19 import java.util.ArrayList;
20 import java.util.LinkedList;
21 import java.util.List;
22
23 import org.springframework.expression.PropertyAccessor;
24
25 /**
26 * Utilities methods for use in the Ast classes.
27 *
28 * @author Andy Clement
29 * @since 3.0.2
30 */
31 public abstract class AstUtils {
32
33 /**
34 * Determines the set of property resolvers that should be used to try and access a
35 * property on the specified target type. The resolvers are considered to be in an
36 * ordered list, however in the returned list any that are exact matches for the input
37 * target type (as opposed to 'general' resolvers that could work for any type) are
38 * placed at the start of the list. In addition, there are specific resolvers that
39 * exactly name the class in question and resolvers that name a specific class but it
40 * is a supertype of the class we have. These are put at the end of the specific resolvers
41 * set and will be tried after exactly matching accessors but before generic accessors.
42 * @param targetType the type upon which property access is being attempted
43 * @return a list of resolvers that should be tried in order to access the property
44 */
45 public static List<PropertyAccessor> getPropertyAccessorsToTry(
46 Class<?> targetType, List<PropertyAccessor> propertyAccessors) {
47
48 List<PropertyAccessor> specificAccessors = new ArrayList<PropertyAccessor>();
49 List<PropertyAccessor> generalAccessors = new ArrayList<PropertyAccessor>();
50 for (PropertyAccessor resolver : propertyAccessors) {
51 Class<?>[] targets = resolver.getSpecificTargetClasses();
52 if (targets == null) { // generic resolver that says it can be used for any type
53 generalAccessors.add(resolver);
54 }
55 else {
56 if (targetType != null) {
57 int pos = 0;
58 for (Class<?> clazz : targets) {
59 if (clazz == targetType) { // put exact matches on the front to be tried first?
60 specificAccessors.add(pos++, resolver);
61 }
62 else if (clazz.isAssignableFrom(targetType)) { // put supertype matches at the end of the
63 // specificAccessor list
64 generalAccessors.add(resolver);
65 }
66 }
67 }
68 }
69 }
70 List<PropertyAccessor> resolvers = new LinkedList<PropertyAccessor>();
71 resolvers.addAll(specificAccessors);
72 resolvers.addAll(generalAccessors);
73 return resolvers;
74 }
75
76 }