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1   /*
2    * Copyright 2002,2004 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,v 1.4 2004/09/01 00:35:38 dion Exp $
25   */
26  public class ASTReference extends SimpleNode
27  {
28      SimpleNode root;
29  
30      public ASTReference(int id)
31      {
32          super(id);
33      }
34  
35      public ASTReference(Parser p, int id)
36      {
37          super(p, id);
38      }
39  
40  
41      /*** Accept the visitor. **/
42      public Object jjtAccept(ParserVisitor visitor, Object data)
43      {
44          return visitor.visit(this, data);
45      }
46  
47      public Object value(JexlContext jc)
48          throws Exception
49      {
50          return  execute(null,jc);
51      }
52  
53      public void jjtClose()
54      {
55          root = (SimpleNode) jjtGetChild(0);
56      }
57  
58      public Object execute(Object obj, JexlContext jc)
59               throws Exception
60       {
61           Object o = root.value(jc);
62  
63           /*
64            * ignore the first child - it's our identifier
65            */
66           for(int i=1; i<jjtGetNumChildren(); i++)
67           {
68               o = ( (SimpleNode) jjtGetChild(i)).execute(o,jc);
69  
70               // check for a variable in the context named
71               // child0.child1.child2 etc
72               if(o == null) {
73                   String varName = getIdentifierToDepth(i);
74                   o = jc.getVars().get(varName);
75               }
76           }
77  
78           return o;
79       }
80  
81      /***
82       * This method returns a variable from this identifier and
83       * it's children. For an expression like 'a.b.c', a is child
84       * zero, b is child 1 and c is child 2.
85       *  
86       * @param i the depth of the child nodes to go to
87       * @return the a dotted variable from this identifier and it's
88       *    child nodes.
89       */
90      private String getIdentifierToDepth(int i) {
91          StringBuffer varName = new StringBuffer();
92           for (int j = 0; j <=i; j++) {
93               SimpleNode node = (SimpleNode) jjtGetChild(j);
94               if (node instanceof ASTIdentifier) {
95                 varName.append(((ASTIdentifier)node).getIdentifierString());
96                 if (j != i) varName.append('.');
97               }
98           }
99          return varName.toString();
100     }
101 
102     public String getRootString()
103         throws Exception
104     {
105         if ( root instanceof ASTIdentifier)
106             return ((ASTIdentifier) root).getIdentifierString();
107 
108         if (root instanceof ASTArrayAccess)
109             return ((ASTArrayAccess) root).getIdentifierString();
110 
111         throw new Exception("programmer error : ASTReference : root not known"
112                     + root );
113     }
114 }