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1   /*
2    * Copyright 2002-2006 The Apache Software Foundation.
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.apache.commons.jexl.parser;
18  
19  import org.apache.commons.jexl.JexlContext;
20  import org.apache.commons.jexl.util.Coercion;
21  import org.apache.commons.jexl.util.Introspector;
22  import org.apache.commons.jexl.util.introspection.Info;
23  import org.apache.commons.jexl.util.introspection.VelPropertyGet;
24  
25  import java.util.List;
26  import java.util.Map;
27  import java.lang.reflect.Array;
28  
29  /***
30   * Like an ASTIdentifier, but with array access allowed.
31   * 
32   * $foo[2]
33   * 
34   * @author <a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
35   * @version $Id: ASTArrayAccess.java 398180 2006-04-29 15:40:35Z dion $
36   */
37  public class ASTArrayAccess extends SimpleNode {
38      /*** dummy velocity info. */
39      private static final Info DUMMY = new Info("", 1, 1);
40  
41      /***
42       * Create the node given an id.
43       * 
44       * @param id node id.
45       */
46      public ASTArrayAccess(int id) {
47          super(id);
48      }
49  
50      /***
51       * Create a node with the given parser and id.
52       * 
53       * @param p a parser.
54       * @param id node id.
55       */
56      public ASTArrayAccess(Parser p, int id) {
57          super(p, id);
58      }
59  
60      /*** {@inheritDoc} */
61      public Object jjtAccept(ParserVisitor visitor, Object data) {
62          return visitor.visit(this, data);
63      }
64  
65      /***
66       * evaluate array access upon a base object.
67       * 
68       * foo.bar[2]
69       * 
70       * makes me rethink the array operator :)
71       * @param jc the {@link JexlContext} to evaluate against.
72       * @param obj not used.
73       * @return the value of the array expression.
74       * @throws Exception on any error
75       */
76      public Object execute(Object obj, JexlContext jc) throws Exception {
77          ASTIdentifier base = (ASTIdentifier) jjtGetChild(0);
78  
79          Object result = base.execute(obj, jc);
80  
81          /*
82           * ignore the first child - it's our identifier
83           */
84          for (int i = 1; i < jjtGetNumChildren(); i++) {
85              Object loc = ((SimpleNode) jjtGetChild(i)).value(jc);
86  
87              if (loc == null) {
88                  return null;
89              }
90  
91              result = evaluateExpr(result, loc);
92          }
93  
94          return result;
95      }
96  
97      /*** {@inheritDoc} */
98      public Object value(JexlContext jc) throws Exception {
99          /*
100          * get the base ASTIdentifier
101          */
102 
103         ASTIdentifier base = (ASTIdentifier) jjtGetChild(0);
104 
105         Object o = base.value(jc);
106 
107         /*
108          * ignore the first child - it's our identifier
109          */
110         for (int i = 1; i < jjtGetNumChildren(); i++) {
111             Object loc = ((SimpleNode) jjtGetChild(i)).value(jc);
112 
113             if (loc == null) {
114                 return null;
115             }
116 
117             o = evaluateExpr(o, loc);
118         }
119 
120         return o;
121     }
122 
123     /***
124      * Evaluate the Array expression 'loc' on the given object, o.
125      * e.g. in 'a[2]', <code>2</code> is 'loc' and <code>a</code> is 'o'.
126      * 
127      * If o or loc are null, null is returned.
128      * If o is a Map, o.get(loc) is returned.
129      * If o is a List, o.get(loc) is returned. loc must resolve to an int value.
130      * If o is an Array, o[loc] is returned. loc must resolve to an int value.
131      * Otherwise loc is treated as a bean property of o.
132      *  
133      * @param o an object to be accessed using the array operator or '.' operator.
134      * @param loc the index of the object to be returned.
135      * @return the resulting value.
136      * @throws Exception on any error.
137      */
138     public static Object evaluateExpr(Object o, Object loc) throws Exception {
139         /*
140          * following the JSTL EL rules
141          */
142 
143         if (o == null) {
144             return null;
145         }
146 
147         if (loc == null) {
148             return null;
149         }
150 
151         if (o instanceof Map) {
152             if (!((Map) o).containsKey(loc)) {
153                 return null;
154             }
155 
156             return ((Map) o).get(loc);
157         } else if (o instanceof List) {
158             int idx = Coercion.coerceInteger(loc).intValue();
159 
160             try {
161                 return ((List) o).get(idx);
162             } catch (IndexOutOfBoundsException iobe) {
163                 return null;
164             }
165         } else if (o.getClass().isArray()) {
166             int idx = Coercion.coerceInteger(loc).intValue();
167 
168             try {
169                 return Array.get(o, idx);
170             } catch (ArrayIndexOutOfBoundsException aiobe) {
171                 return null;
172             }
173         } else {
174             /*
175              * "Otherwise (a JavaBean object)..." huh? :)
176              */
177 
178             String s = loc.toString();
179 
180             VelPropertyGet vg = Introspector.getUberspect().getPropertyGet(o, s, DUMMY);
181 
182             if (vg != null) {
183                 return vg.invoke(o);
184             }
185         }
186 
187         throw new Exception("Unsupported object type for array [] accessor");
188     }
189 
190     /***
191      * Gets the variable name piece of the expression.
192      * @return a String of the identifer. 
193      * @see ASTIdentifier#getIdentifierString().
194      */
195     public String getIdentifierString() {
196         return ((ASTIdentifier) jjtGetChild(0)).getIdentifierString();
197     }
198 }