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Java > Open Source Codes > org > apache > velocity > runtime > parser > node > NodeUtils


1 package org.apache.velocity.runtime.parser.node;
2 /*
3  * Copyright 2000-2001,2004 The Apache Software Foundation.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17
18 import org.apache.velocity.context.Context;
19 import org.apache.velocity.runtime.parser.*;
20
21 /**
22  * Utilities for dealing with the AST node structure.
23  *
24  * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
25  * @author <a HREF="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
26  * @version $Id: NodeUtils.java,v 1.16.4.1 2004/03/03 23:22:59 geirm Exp $
27  */
28 public class NodeUtils
29 {
30     /**
31      * Collect all the <SPECIAL_TOKEN>s that
32      * are carried along with a token. Special
33      * tokens do not participate in parsing but
34      * can still trigger certain lexical actions.
35      * In some cases you may want to retrieve these
36      * special tokens, this is simply a way to
37      * extract them.
38      */
39     public static String JavaDoc specialText(Token t)
40     {
41         String JavaDoc specialText = "";
42         
43         if (t.specialToken == null || t.specialToken.image.startsWith("##") )
44             return specialText;
45             
46         Token tmp_t = t.specialToken;
47
48         while (tmp_t.specialToken != null)
49         {
50             tmp_t = tmp_t.specialToken;
51         }
52
53         while (tmp_t != null)
54         {
55             String JavaDoc st = tmp_t.image;
56
57             StringBuffer JavaDoc sb = new StringBuffer JavaDoc();
58
59             for(int i = 0; i < st.length(); i++)
60             {
61                 char c = st.charAt(i);
62
63                 if ( c == '#' || c == '$' )
64                 {
65                     sb.append( c );
66                 }
67
68                 /*
69                  * more dreaded MORE hack :)
70                  *
71                  * looking for ("\\")*"$" sequences
72                  */
73
74                 if ( c == '\\')
75                 {
76                     boolean ok = true;
77                     boolean term = false;
78
79                     int j = i;
80                     for( ok = true; ok && j < st.length(); j++)
81                     {
82                         char cc = st.charAt( j );
83                  
84                         if (cc == '\\')
85                         {
86                             /*
87                              * if we see a \, keep going
88                              */
89                             continue;
90                         }
91                         else if( cc == '$' )
92                         {
93                             /*
94                              * a $ ends it correctly
95                              */
96                             term = true;
97                             ok = false;
98                         }
99                         else
100                         {
101                             /*
102                              * nah...
103                              */
104                             ok = false;
105                         }
106                     }
107
108                     if (term)
109                     {
110                         String JavaDoc foo = st.substring( i, j );
111                         sb.append( foo );
112                         i = j;
113                     }
114                 }
115             }
116             
117             specialText += sb.toString();
118
119             tmp_t = tmp_t.next;
120         }
121
122         return specialText;
123     }
124     
125     /**
126      * complete node literal
127      *
128      */
129     public static String JavaDoc tokenLiteral( Token t )
130     {
131         return specialText( t ) + t.image;
132     }
133     
134     /**
135      * Utility method to interpolate context variables
136      * into string literals. So that the following will
137      * work:
138      *
139      * #set $name = "candy"
140      * $image.getURI("${name}.jpg")
141      *
142      * And the string literal argument will
143      * be transformed into "candy.jpg" before
144      * the method is executed.
145      */
146     public static String JavaDoc interpolate(String JavaDoc argStr, Context vars)
147     {
148         StringBuffer JavaDoc argBuf = new StringBuffer JavaDoc();
149
150         for (int cIdx = 0 ; cIdx < argStr.length();)
151         {
152             char ch = argStr.charAt(cIdx);
153
154             switch (ch)
155             {
156                 case '$':
157                     StringBuffer JavaDoc nameBuf = new StringBuffer JavaDoc();
158                     for (++cIdx ; cIdx < argStr.length(); ++cIdx)
159                     {
160                         ch = argStr.charAt(cIdx);
161                         if (ch == '_' || ch == '-'
162                             || Character.isLetterOrDigit(ch))
163                             nameBuf.append(ch);
164                         else if (ch == '{' || ch == '}')
165                             continue;
166                         else
167                             break;
168                     }
169
170                     if (nameBuf.length() > 0)
171                     {
172                         Object JavaDoc value = vars.get(nameBuf.toString());
173
174                         if (value == null)
175                             argBuf.append("$").append(nameBuf.toString());
176                         else
177                             argBuf.append(value.toString());
178                     }
179                     break;
180
181                 default:
182                     argBuf.append(ch);
183                     ++cIdx;
184                     break;
185             }
186         }
187
188         return argBuf.toString();
189     }
190 }
191
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