CalcTag


1   /**
2    * Copyright (C) 2001 Yasna.com. All rights reserved.
3    *
4    * ===================================================================
5    * The Apache Software License, Version 1.1
6    *
7    * Redistribution and use in source and binary forms, with or without
8    * modification, are permitted provided that the following conditions
9    * are met:
10   *
11   * 1. Redistributions of source code must retain the above copyright
12   *    notice, this list of conditions and the following disclaimer.
13   *
14   * 2. Redistributions in binary form must reproduce the above copyright
15   *    notice, this list of conditions and the following disclaimer in
16   *    the documentation and/or other materials provided with the
17   *    distribution.
18   *
19   * 3. The end-user documentation included with the redistribution,
20   *    if any, must include the following acknowledgment:
21   *       "This product includes software developed by
22   *        Yasna.com (http://www.yasna.com)."
23   *    Alternately, this acknowledgment may appear in the software itself,
24   *    if and wherever such third-party acknowledgments normally appear.
25   *
26   * 4. The names "Yazd" and "Yasna.com" must not be used to
27   *    endorse or promote products derived from this software without
28   *    prior written permission. For written permission, please
29   *    contact yazd@yasna.com.
30   *
31   * 5. Products derived from this software may not be called "Yazd",
32   *    nor may "Yazd" appear in their name, without prior written
33   *    permission of Yasna.com.
34   *
35   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
36   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
37   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
38   * DISCLAIMED.  IN NO EVENT SHALL YASNA.COM OR
39   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
41   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
42   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
43   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
44   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
45   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
46   * SUCH DAMAGE.
47   * ====================================================================
48   *
49   * This software consists of voluntary contributions made by many
50   * individuals on behalf of Yasna.com. For more information
51   * on Yasna.com, please see <http://www.yasna.com>.
52   */
53  
54  /**
55   * Copyright (C) 2000 CoolServlets.com. All rights reserved.
56   *
57   * ===================================================================
58   * The Apache Software License, Version 1.1
59   *
60   * Redistribution and use in source and binary forms, with or without
61   * modification, are permitted provided that the following conditions
62   * are met:
63   *
64   * 1. Redistributions of source code must retain the above copyright
65   *    notice, this list of conditions and the following disclaimer.
66   *
67   * 2. Redistributions in binary form must reproduce the above copyright
68   *    notice, this list of conditions and the following disclaimer in
69   *    the documentation and/or other materials provided with the
70   *    distribution.
71   *
72   * 3. The end-user documentation included with the redistribution,
73   *    if any, must include the following acknowledgment:
74   *       "This product includes software developed by
75   *        CoolServlets.com (http://www.coolservlets.com)."
76   *    Alternately, this acknowledgment may appear in the software itself,
77   *    if and wherever such third-party acknowledgments normally appear.
78   *
79   * 4. The names "Jive" and "CoolServlets.com" must not be used to
80   *    endorse or promote products derived from this software without
81   *    prior written permission. For written permission, please
82   *    contact webmaster@coolservlets.com.
83   *
84   * 5. Products derived from this software may not be called "Jive",
85   *    nor may "Jive" appear in their name, without prior written
86   *    permission of CoolServlets.com.
87   *
88   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
89   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
90   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
91   * DISCLAIMED.  IN NO EVENT SHALL COOLSERVLETS.COM OR
92   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
93   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
94   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
95   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
96   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
97   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
98   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
99   * SUCH DAMAGE.
100  * ====================================================================
101  *
102  * This software consists of voluntary contributions made by many
103  * individuals on behalf of CoolServlets.com. For more information
104  * on CoolServlets.com, please see <http://www.coolservlets.com>.
105  */
106 
107 package com.Yasna.forum.tags;
108 
109 import java.io.*;
110 import java.util.*;
111 import javax.servlet.*;
112 import javax.servlet.jsp.*;
113 import javax.servlet.jsp.tagext.*;
114 import javax.servlet.http.*;
115 import com.Yasna.forum.tags.*;
116 
117 /**
118  * JSP Tag <b>calc</b>, used to calculate and return an integer value.
119  * <p>
120  * Calculates an integer value based on the integer values and operators
121  * found in the body of the calc tag, then returns the value calculated
122  * to the JSP page.
123  * <p>
124  * Valid operators are <b>+</b>, <b>-</b>, <b>*</b>, and <b>/</b>.
125  * <p>
126  * There must be white space between integers and operators.
127  * <p>
128  * Any JSP tags embedded in the body of the calc tag are processed
129  * before the calculation is made.
130  * <p>
131  * Example:
132  * <p>
133  * &lt;jf:calc&gt; &lt;jf:current_depth/&gt; * 4 &lt;/jf:calc&gt;
134  * <p>
135  * JSP Tag Lib Descriptor
136  * <p><pre>
137  *  &lt;name&gt;calc&lt;/name&gt;
138  *  &lt;tagclass&gt;com.Yasna.forum.tags.CalcTag&lt;/tagclass&gt;
139  *  &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
140  *  &lt;info&gt;Calculate an expression&lt;/info&gt;
141  * </pre>
142  *
143  * @author Glenn Nielsen
144  */
145 
146 public class CalcTag extends BodyTagSupport
147 {
148   // Result of integer calculation
149   long res = 0;
150 
151   /**
152    * Allow the body of the calc tag to be processed.
153    *
154    * @return EVAL_BODY_TAG
155    */
156   public final int doStartTag() throws JspException
157   {
158     return EVAL_BODY_TAG;
159   }
160 
161   /**
162    * Read the body of the calc tag to obtain the integer values and operators,
163    * then perform calculation.
164    *
165    * @return SKIP_BODY
166    */
167   public final int doAfterBody() throws JspException
168   {
169     // Use the body of the tag as input for the calculation
170     BodyContent body = getBodyContent();
171     String   s = body.getString();
172     // Clear the body since we will output only the result of the calculation
173     body.clearBody();
174 
175     // Create a list of integers and operators
176     List l = new LinkedList();
177     int beg = 0,end=0;
178     int len = s.length();
179     char v;
180     boolean digit = false;
181     boolean operator = false;
182     boolean negated = false;
183 
184     // Parse the body extracting integers and operators
185     for( end=0; end < len; end++ ) {
186       v = s.charAt(end);
187 //      System.out.println("calc char \"" + v + "\" negated=" + negated);
188       if( Character.isWhitespace(v) ) {
189         if( digit ) {
190 //          System.out.println("Calc digit \"" + s.substring(beg,end) + "\"");
191           l.add((Object  )Long.valueOf(s.substring(beg,end)));
192         } else if( operator ) {
193 //          System.out.println("Calc op \"" + s.substring(beg,end) + "\"");
194           l.add((Object  )new StringBuffer  (s.substring(beg,end)));
195         }
196         digit = negated = operator = false;
197         beg = end;
198       } else if( Character.isDigit(v) ) {
199         if( !operator || negated ) {
200           if( !digit && !negated )beg = end;
201           digit = true;
202           operator = negated = false;
203         }
204       } else {
205         if( !operator && !digit) {
206           beg = end;
207           if( v == '-' )
208             negated = true;
209         } else {
210           negated = false;
211         }
212         operator = true;
213         digit = false;
214       }
215     }
216 
217     if( (end - beg) > 0 ) {
218       if( digit ) {
219 //  System.out.println("Calc digit \"" + s.substring(beg,end) + "\"");
220         l.add((Object  )Long.valueOf(s.substring(beg,end)));
221       } else if( operator ) {
222 //  System.out.println("Calc op \"" + s.substring(beg,end) + "\"");
223         l.add((Object  )new StringBuffer  (s.substring(beg,end)));
224       }
225     }
226     // Calculate the result
227     res = calculate((ListIterator)l.iterator());
228 //    System.out.println("calc result: " + res);
229     return SKIP_BODY;
230   }
231 
232   /**
233    * Output the result of the calculation
234    *
235    * @return EVAL_PAGE
236    */
237 
238   public final int doEndTag() throws JspException
239   {
240     try {
241       pageContext.getOut().write("" + res);
242     } catch(Exception   e) {
243       throw new JspException("IO Error: " + e.getMessage());
244     }
245     return EVAL_PAGE;
246   }
247 
248   /**
249    * Do the calculation
250    *
251    * @return String - result of the calculation as an integer
252    */
253   private long calculate(ListIterator li) throws JspException
254   {
255     long a = 0;
256     long res = 0;
257     StringBuffer   sb = null;
258     Object   o;
259     Long   v;
260     boolean aset = false;
261 
262     // Loop through the list of integers and operators
263     // performing calculations
264     while(li.hasNext()) {
265       o = li.next();
266       if( o.getClass().getName().equals("java.lang.Long") ) {
267     v = (Long  )o;
268 //  System.out.println("Calc value: " + v.longValue());
269     if( aset ) {
270       if( sb == null ) {
271         throw new JspException("Jive tag calc missing operator.");
272       }
273 //    System.out.println("Calc operator: " + sb);
274       if( sb.toString().equals("*") )
275         a *= v.longValue();
276       else if( sb.toString().equals("+") )
277         a += v.longValue();
278           else if( sb.toString().equals("/") )
279             a /= v.longValue();
280           else if( sb.toString().equals("-") )
281             a -= v.longValue();
282       else
283         throw new JspException("Jive tag calc invalid operator \"" +
284         sb + "\"");
285     } else {
286       aset = true;
287       a = v.longValue();
288     }
289       } else {
290     sb = (StringBuffer  )o;
291         if( !aset ) {
292       throw new JspException("Jive tag calc must start with a number.");
293     }
294       }
295     }
296     return a;
297   }
298 
299 }
300
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