MonthsTag


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.datetime;
18  
19  import java.util.*;
20  import java.text.*;
21  import javax.servlet.*;
22  import javax.servlet.http.*;
23  import javax.servlet.jsp.*;
24  import javax.servlet.jsp.tagext.*;
25  
26  /**
27   * JSP Tag <b>months</b>, used to loop through all the months of the year
28   * so that month names can be accessed by using the standard
29   * JSP &lt;jsp:getProperty&gt; tag.
30   * <p>
31   * The script variable of name <b>id</b> is availble only within the
32   * body of the <b>months</b> tag.
33   * <p>
34   * Loops through all the months.
35   * <p>
36   * If the optional attribute <b>locale</b> is true, the month names
37   * are formatted for the clients locale if known.
38   * <p>
39   * The optional attribute <b>localeRef</b> can be used to specify
40   * the name of a page, session, application, or request scope attribute
41   * of type java.util.Locale to use.
42   * <p>
43   * JSP Tag Lib Descriptor
44   * <p><pre>
45   * &lt;name&gt;months&lt;/name&gt;
46   * &lt;tagclass&gt;org.apache.taglibs.datetime.MonthsTag&lt;/tagclass&gt;
47   * &lt;teiclass&gt;org.apache.taglibs.datetime.MonthsTEI&lt;/teiclass&gt;
48   * &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
49   * &lt;info&gt;Loop through all the months of the year.&lt;/info&gt;
50   *   &lt;attribute&gt;
51   *     &lt;name&gt;id&lt;/name&gt;
52   *     &lt;required&gt;true&lt;/required&gt;
53   *     &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
54   *   &lt;/attribute&gt;
55   *   &lt;attribute&gt;
56   *     &lt;name&gt;locale&lt;/name&gt;
57   *     &lt;required&gt;false&lt;/required&gt;
58   *     &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
59   *   &lt;/attribute&gt;
60   *   &lt;attribute&gt;                             
61   *     &lt;name&gt;localeRef&lt;/name&gt;
62   *     &lt;required&gt;false&lt;/required&gt;
63   *     &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
64   *   &lt;/attribute&gt;
65   * </pre>
66   *
67   * @author Glenn Nielsen
68   */
69  
70  public class MonthsTag extends BodyTagSupport
71  {
72      // Static constants                     
73      private static String   PATTERN = "yyyy";
74  
75      // months tag attributes
76      private boolean locale_flag = false;
77      private String   localeRef = null;
78  
79      // months tag invocation variables
80      private String   [] short_months = null;
81      private String   [] long_months = null;
82      private int month = 0;
83      private int month_num = 1;
84  
85      /**
86       * Initializes tag so it can loop through the months of the year.
87       *
88       * @return EVAL_BODY_TAG
89       */
90      public final int doStartTag() throws JspException
91      {
92          // Initialize variables
93          month = 0;
94          month_num = 1;
95  
96          SimpleDateFormat sdf;
97          // Get a SimpleDateFormat using locale if necessary
98          if( localeRef != null ) {
99              Locale locale = (Locale)pageContext.findAttribute(localeRef);
100             if( locale == null ) {
101                 throw new JspException(
102                     "datetime amPms tag could not find locale for localeRef \"" +
103                     localeRef + "\".");
104             }
105  
106             sdf = new SimpleDateFormat(PATTERN,locale);
107         } else if( locale_flag ) {
108             sdf = new SimpleDateFormat(PATTERN,
109                       (Locale)pageContext.getRequest().getLocale());
110         } else {
111             sdf = new SimpleDateFormat(PATTERN);
112         }
113 
114     DateFormatSymbols dfs = sdf.getDateFormatSymbols();
115     short_months = dfs.getShortMonths();
116     long_months = dfs.getMonths();
117     // Make sure we skip any blank array elements
118         while( month < long_months.length && 
119             (long_months[month] == null || long_months[month].length() == 0) )
120                 month++;
121         if( month >= short_months.length )
122             return SKIP_BODY;
123 
124     pageContext.setAttribute(id,this,PageContext.PAGE_SCOPE);
125     return EVAL_BODY_TAG;
126     }
127 
128     /**
129      * Method called at end of each months tag.
130      *
131      * @return EVAL_BODY_TAG if there is another month, or SKIP_BODY if there are no more months
132      */
133     public final int doAfterBody() throws JspException
134     {
135     // See if we are done looping through months
136     month++;
137     month_num++;
138         if( month >= short_months.length )
139             return SKIP_BODY;
140     // Make sure we skip any blank array elements
141         while( month < long_months.length && 
142         (long_months[month] == null || long_months[month].length() == 0) )
143                 month++;
144 
145     if( month >= short_months.length )
146         return SKIP_BODY;
147 
148     // There is another month, so loop again
149     return EVAL_BODY_TAG;
150     }
151 
152     /**
153      * Method called at end of Tag
154      * @return EVAL_PAGE
155      */
156     public final int doEndTag() throws JspException
157     {
158         pageContext.removeAttribute(id,PageContext.PAGE_SCOPE);
159     try
160     {
161         if(bodyContent != null)
162         bodyContent.writeOut(bodyContent.getEnclosingWriter());
163     } catch(java.io.IOException   e)
164     {
165         throw new JspException("IO Error: " + e.getMessage());
166     }
167     return EVAL_PAGE;
168     }
169 
170     /**
171      * Locale flag, if set to true, use month names
172      * for client's preferred locale if known.
173      *
174      * @param boolean either <b>true</b> or <b>false</b>
175      */
176     public final void setLocale(boolean flag)
177     {
178         locale_flag = flag;
179     }
180 
181     /**
182      * Returns the short name of the month.
183      * <p>
184      * &lt;jsp:getProperty name=<i>"id"</i> property="shortMonth"/&gt;
185      *
186      * @return String - short name of the month
187      */
188     public final String   getShortMonth()
189     {
190     return short_months[month];
191     }
192 
193     /**
194      * Returns the long name of the month.
195      * <p>
196      * &lt;jsp:getProperty name=<i>"id"</i> property="month"/&gt;
197      *
198      * @return String - long name of the month
199      */
200     public final String   getMonth()
201     {  
202         return long_months[month];
203     }
204 
205     /**
206      * Provides a key to search the page context for in order to get the
207      * java.util.Locale to use.
208      *
209      * @param String name of locale attribute to use
210      */
211     public void setLocaleRef(String   value)
212     {
213         localeRef = value;
214     }
215 
216     /**
217      * Returns the number of the month.
218      * <p>         
219      * &lt;jsp:getProperty name=<i>"id"</i> property="monthOfYear"/&gt;
220      *             
221      * @return String - number of the month
222      */            
223     public final String   getMonthOfYear()
224     {              
225     if( month_num < 10 )
226         return "0" + month_num;
227         return "" + month_num;
228     }
229 
230 }
231
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