KickJava   Java API By Example, From Geeks To Geeks.

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


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 package org.apache.commons.jexl.parser;
17
18 import org.apache.commons.jexl.JexlContext;
19
20 /**
21  * reference - any variable expression.
22  *
23  * @author <a HREF="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
24  * @version $Id: ASTReference.java 398272 2006-04-30 03:14:01Z dion $
25  */
26 public class ASTReference extends SimpleNode {
27     /** first variable in the expression. */
28     protected SimpleNode root;
29
30     /**
31      * Create the node given an id.
32      *
33      * @param id node id.
34      */
35     public ASTReference(int id) {
36         super(id);
37     }
38
39     /**
40      * Create a node with the given parser and id.
41      *
42      * @param p a parser.
43      * @param id node id.
44      */
45     public ASTReference(Parser p, int id) {
46         super(p, id);
47     }
48
49     /** {@inheritDoc} */
50     public Object JavaDoc jjtAccept(ParserVisitor visitor, Object JavaDoc data) {
51         return visitor.visit(this, data);
52     }
53
54     /** {@inheritDoc} */
55     public Object JavaDoc value(JexlContext jc) throws Exception JavaDoc {
56         return execute(null, jc);
57     }
58
59     /** Store the first child as {@link ASTReference#root root}. */
60     public void jjtClose() {
61         root = (SimpleNode) jjtGetChild(0);
62     }
63
64     /**
65      * evaluate each piece of the reference.
66      *
67      * e.g. foo.bar.woogie[2].name, foo is our 'root', and we need to
68      * evaluate 'bar.woogie[2].name' relative to foo.
69      *
70      * @param jc the {@link JexlContext} to evaluate against.
71      * @param obj not used. root.value(jc) is used instead.
72      * @return the value of the array expression.
73      * @throws Exception on any error
74      */
75     public Object JavaDoc execute(Object JavaDoc obj, JexlContext jc) throws Exception JavaDoc {
76         Object JavaDoc o = root.value(jc);
77
78         /*
79          * ignore the first child - it's our identifier
80          */
81         for (int i = 1; i < jjtGetNumChildren(); i++) {
82             o = ((SimpleNode) jjtGetChild(i)).execute(o, jc);
83
84             // check for a variable in the context named
85 // child0.child1.child2 etc
86 if (o == null) {
87                 String JavaDoc varName = getIdentifierToDepth(i);
88                 o = jc.getVars().get(varName);
89             }
90         }
91
92         return o;
93     }
94
95     /**
96      * This method returns a variable from this identifier and it's children.
97      * For an expression like 'a.b.c', a is child zero, b is child 1 and c is
98      * child 2.
99      *
100      * @param i the depth of the child nodes to go to
101      * @return the a dotted variable from this identifier and it's child nodes.
102      */
103     private String JavaDoc getIdentifierToDepth(int i) {
104         StringBuffer JavaDoc varName = new StringBuffer JavaDoc();
105         for (int j = 0; j <= i; j++) {
106             SimpleNode node = (SimpleNode) jjtGetChild(j);
107             if (node instanceof ASTIdentifier) {
108                 varName.append(((ASTIdentifier) node).getIdentifierString());
109                 if (j != i) {
110                     varName.append('.');
111                 }
112             }
113         }
114         return varName.toString();
115     }
116
117     /**
118      * Gets the variable name of {@link ASTReference#root root}.
119      * @return the identifier.
120      * @throws Exception on any error
121      * @see ASTIdentifier#getIdentifierString()
122      * @see ASTArrayAccess#getIdentifierString()
123      */
124     public String JavaDoc getRootString() throws Exception JavaDoc {
125         if (root instanceof ASTIdentifier) {
126             return ((ASTIdentifier) root).getIdentifierString();
127         }
128
129         if (root instanceof ASTArrayAccess) {
130             return ((ASTArrayAccess) root).getIdentifierString();
131         }
132
133         throw new Exception JavaDoc("programmer error : ASTReference : root not known" + root);
134     }
135 }
136
Popular Tags