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1   /*
2    * $Id: ELMatchSupport.java 471754 2006-11-06 14:55:09Z husted $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  package org.apache.strutsel.taglib.logic;
22  
23  import org.apache.struts.taglib.TagUtils;
24  import org.apache.struts.util.MessageResources;
25  
26  import javax.servlet.jsp.JspException;
27  import javax.servlet.jsp.PageContext;
28  
29  /**
30   * This class is used as a helper class for both the <code>org.apache.strutsel.taglib.logic.ELMatchTag</code>
31   * and <code>org.apache.strutsel.taglib.logic.ELNotMatchTag</code> classes.
32   * It's <code>condition</code> method encapsulates the common logic needed to
33   * examine the <code>location</code> attribute to determine how to do the
34   * comparison.
35   */
36  class ELMatchSupport {
37      /**
38       * Performs a comparison of an expression and a value, with an optional
39       * location specifier in the expression (start or end).
40       *
41       * @param desired     Indication of whether the "truth" value of the
42       *                    comparison is whether the expression and value are
43       *                    equal, or not equal.
44       * @param expr        Expression to test against a value.
45       * @param value       Value to test against an expression.
46       * @param location    if set, is "start" or "end" to indicate to look at
47       *                    the start or end of the expression for the value.
48       *                    If null, look anywhere in the expression.
49       * @param messages    <code>MessageResources</code> object to reference
50       *                    for error message text.
51       * @param pageContext used to save exception information, if needed.
52       * @return true if comparison result equals desired value, false
53       *         otherwise.
54       */
55      public static boolean condition(boolean desired, String expr, String value,
56          String location, MessageResources messages, PageContext pageContext)
57          throws JspException {
58          boolean result = false;
59  
60          if (expr != null) {
61              // Perform the comparison requested by the location attribute
62              boolean matched = false;
63  
64              if (location == null) {
65                  matched = (expr.indexOf(value) >= 0);
66              } else if (location.equals("start")) {
67                  matched = expr.startsWith(value);
68              } else if (location.equals("end")) {
69                  matched = expr.endsWith(value);
70              } else {
71                  JspException e =
72                      new JspException(messages.getMessage("logic.location",
73                              location));
74  
75                  TagUtils.getInstance().saveException(pageContext, e);
76                  throw e;
77              }
78  
79              result = (matched == desired);
80          }
81  
82          return (result);
83      }
84  }