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Java > Open Source Codes > org > apache > taglibs > standard > lang > jpath > expression > SubstringFunction


1 /*
2  * Copyright 1999,2004 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
17 package org.apache.taglibs.standard.lang.jpath.expression;
18
19 import javax.servlet.jsp.PageContext JavaDoc;
20
21 import org.apache.taglibs.standard.lang.jpath.adapter.ConversionException;
22 import org.apache.taglibs.standard.lang.jpath.adapter.Convert;
23 import org.apache.taglibs.standard.lang.jpath.adapter.IterationContext;
24
25 /**
26  * The SubstringFunction class
27  *
28  *
29  * @author <a HREF='mailto:scott.hasse@isthmusgroup.com'>Scott Hasse</a>
30  * @version
31  */
32 public class SubstringFunction extends SimpleNode {
33
34     /**
35      * Used to create an instance of the SubstringFunction class
36      *
37      *
38      * @param id
39      *
40      */
41     public SubstringFunction(int id) {
42         super(id);
43     }
44
45     /**
46      * Used to create an instance of the SubstringFunction class
47      *
48      *
49      * @param p
50      * @param id
51      *
52      */
53     public SubstringFunction(Parser p, int id) {
54         super(p, id);
55     }
56
57     /**
58      * Provides a method to print a normalized version of the original
59      * expression. The normalized version has standardized spacing and
60      * parenthesis, and can be used to compare expressions formatted
61      * in different ways to see if they are actually the same expression.
62      *
63      *
64      * @return The normalized version of the original expression
65      *
66      */
67     public String JavaDoc toNormalizedString() {
68
69         boolean first = true;
70         String JavaDoc normalized;
71
72         normalized = "substring(";
73
74         if (children != null) {
75             for (int i = 0; i < children.length; ++i) {
76                 if (!first) {
77                     normalized = normalized + ",";
78                 }
79
80                 first = false;
81
82                 SimpleNode n = (SimpleNode) children[i];
83
84                 if (n != null) {
85                     normalized = normalized + n.toNormalizedString();
86                 }
87             }
88         }
89
90         normalized = normalized + ")";
91
92         return normalized;
93     }
94
95     /**
96      * This method evaluates this node of the expression and all child nodes.
97      * It returns the result of the
98      * evaluation as an <tt>Object</tt>. If any problems are encountered
99      * during the evaluation, an <tt>EvaluationException</tt> is thrown.
100      *
101      *
102      * @param pageContext the current JSP PageContext
103      *
104      * @param icontext the Iteration Context of the expression. If there is
105      * no interation context, this should be null.
106      *
107      * @return the result of the expression evaluation as an object
108      *
109      * @throws EvaluationException if a problem is encountered during the
110      * evaluation
111      */
112     public Object JavaDoc evaluate(PageContext JavaDoc pageContext, IterationContext icontext)
113             throws EvaluationException {
114
115         String JavaDoc result;
116
117         try {
118             String JavaDoc arg1 =
119                 Convert.toString(jjtGetChild(0).evaluate(pageContext,
120                     icontext));
121             int arg2 = Convert.toDouble(jjtGetChild(1).evaluate(pageContext,
122                            icontext)).intValue();
123
124             if (jjtGetNumChildren() > 2) {
125                 int arg3 =
126                     Convert.toDouble(jjtGetChild(2).evaluate(pageContext,
127                         icontext)).intValue();
128
129                 result = arg1.substring(arg2, arg3);
130             } else {
131                 result = arg1.substring(arg2);
132             }
133         } catch (ConversionException ce) {
134             throw new EvaluationException(this, ce.getMessage());
135         }
136
137         return result;
138     }
139 }
140
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