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Java > Open Source Codes > org > apache > commons > jexl > parser > ASTArrayAccess


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 JavaDoc;
26 import java.util.Map JavaDoc;
27 import java.lang.reflect.Array JavaDoc;
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 JavaDoc jjtAccept(ParserVisitor visitor, Object JavaDoc 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 JavaDoc execute(Object JavaDoc obj, JexlContext jc) throws Exception JavaDoc {
77         ASTIdentifier base = (ASTIdentifier) jjtGetChild(0);
78
79         Object JavaDoc 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 JavaDoc 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 JavaDoc value(JexlContext jc) throws Exception JavaDoc {
99         /*
100          * get the base ASTIdentifier
101          */
102
103         ASTIdentifier base = (ASTIdentifier) jjtGetChild(0);
104
105         Object JavaDoc 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 JavaDoc 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 JavaDoc evaluateExpr(Object JavaDoc o, Object JavaDoc loc) throws Exception JavaDoc {
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 JavaDoc) {
152             if (!((Map JavaDoc) o).containsKey(loc)) {
153                 return null;
154             }
155
156             return ((Map JavaDoc) o).get(loc);
157         } else if (o instanceof List JavaDoc) {
158             int idx = Coercion.coerceInteger(loc).intValue();
159
160             try {
161                 return ((List JavaDoc) o).get(idx);
162             } catch (IndexOutOfBoundsException JavaDoc 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 JavaDoc aiobe) {
171                 return null;
172             }
173         } else {
174             /*
175              * "Otherwise (a JavaBean object)..." huh? :)
176              */
177
178             String JavaDoc 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 JavaDoc("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 JavaDoc getIdentifierString() {
196         return ((ASTIdentifier) jjtGetChild(0)).getIdentifierString();
197     }
198 }
199
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