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Java > Open Source Codes > org > apache > tapestry > script > AbstractToken


1 // Copyright 2004, 2005 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.tapestry.script;
16
17 import java.util.ArrayList JavaDoc;
18 import java.util.Iterator JavaDoc;
19 import java.util.List JavaDoc;
20
21 import org.apache.hivemind.ApplicationRuntimeException;
22 import org.apache.hivemind.Location;
23 import org.apache.tapestry.services.ExpressionEvaluator;
24
25 /**
26  * Base class for creating tokens which may contain other tokens.
27  *
28  * @author Howard Lewis Ship
29  * @since 0.2.9
30  */
31
32 abstract class AbstractToken implements IScriptToken
33 {
34     private List JavaDoc _tokens;
35
36     private Location _location;
37
38     protected AbstractToken(Location location)
39     {
40         _location = location;
41     }
42
43     public Location getLocation()
44     {
45         return _location;
46     }
47
48     public void addToken(IScriptToken token)
49     {
50         if (_tokens == null)
51             _tokens = new ArrayList JavaDoc();
52
53         _tokens.add(token);
54     }
55
56     /**
57      * Invokes {@link IScriptToken#write(StringBuffer,ScriptSession)}on each child token (if there
58      * are any).
59      */
60
61     protected void writeChildren(StringBuffer JavaDoc buffer, ScriptSession session)
62     {
63         if (_tokens == null)
64             return;
65
66         Iterator JavaDoc i = _tokens.iterator();
67
68         while (i.hasNext())
69         {
70             IScriptToken token = (IScriptToken) i.next();
71
72             token.write(buffer, session);
73         }
74     }
75
76     /**
77      * Evaluates the expression against the session's symbols, using
78      * {@link ExpressionEvaluator#read(Object, String)}and returns the result.
79      */
80     protected Object JavaDoc evaluate(String JavaDoc expression, ScriptSession session)
81     {
82
83         try
84         {
85             return session.evaluate(expression);
86         }
87         catch (Exception JavaDoc ex)
88         {
89             throw new ApplicationRuntimeException(ex.getMessage(), _location, ex);
90         }
91     }
92
93     /**
94      * Evaluates an expression and coerces the result to a boolean.
95      *
96      * @since 4.0
97      */
98
99     protected boolean evaluateBoolean(String JavaDoc expression, ScriptSession session)
100     {
101         try
102         {
103             Boolean JavaDoc b = (Boolean JavaDoc) session.evaluate(expression, Boolean JavaDoc.class);
104
105             return b.booleanValue();
106         }
107         catch (Exception JavaDoc ex)
108         {
109             throw new ApplicationRuntimeException(ex.getMessage(), _location, ex);
110         }
111     }
112 }
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