View Javadoc

1   /*
2    * $Id: IteratorComponent.java 497654 2007-01-19 00:21:57Z rgielen $
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.struts2.components;
22  
23  import java.io.Writer;
24  import java.util.Iterator;
25  
26  import org.apache.struts2.views.annotations.StrutsTag;
27  import org.apache.struts2.views.annotations.StrutsTagAttribute;
28  import org.apache.struts2.util.MakeIterator;
29  import org.apache.struts2.views.jsp.IteratorStatus;
30  
31  import com.opensymphony.xwork2.util.ValueStack;
32  
33  /***
34   * <!-- START SNIPPET: javadoc -->
35   *
36   * <p>Iterator will iterate over a value. An iterable value can be either of: java.util.Collection, java.util.Iterator,
37   * java.util.Enumeration, java.util.Map, array.</p> <p/> <!-- END SNIPPET: javadoc -->
38   *
39   * <!-- START SNIPPET: params -->
40   *
41   * <ul>
42   *
43   * <li>status (String) - if specified, an instanceof IteratorStatus will be pushed into stack upon each iteration</li>
44   *
45   * <li>value (Object) - the source to iterate over, must be iteratable, else an the object itself will be put into a
46   * newly created List (see MakeIterator#convert(Object)</li>
47   *
48   * <li>id (String) - if specified the current iteration object will be place with this id in Struts stack's context
49   * scope</li>
50   *
51   * </ul>
52   *
53   * <!-- END SNIPPET: params -->
54   *
55   * <!-- START SNIPPET: example1description -->
56   *
57   * <p>The following example retrieves the value of the getDays() method of the current object on the value stack and
58   * uses it to iterate over. The &lt;s:property/&gt; tag prints out the current value of the iterator.</p>
59   *
60   * <!-- END SNIPPET: example1description -->
61   *
62   * <pre>
63   * <!-- START SNIPPET: example1code -->
64   * &lt;s:iterator value="days"&gt;
65   *   &lt;p&gt;day is: &lt;s:property/&gt;&lt;/p&gt;
66   * &lt;/s:iterator&gt;
67   * <!-- END SNIPPET: example1code -->
68   * </pre>
69   *
70   *
71   * <!-- START SNIPPET: example2description -->
72   *
73   * <p>The following example uses a {@link Bean} tag and places it into the ActionContext. The iterator tag will retrieve
74   * that object from the ActionContext and then calls its getDays() method as above. The status attribute is also used to
75   * create a {@link IteratorStatus} object, which in this example, its odd() method is used to alternate row
76   * colours:</p>
77   *
78   * <!-- END SNIPPET: example2description -->
79   *
80   *
81   * <pre>
82   * <!-- START SNIPPET: example2code -->
83   *
84   * &lt;s:bean name="org.apache.struts2.example.IteratorExample" id="it"&gt;
85   *   &lt;s:param name="day" value="'foo'"/&gt;
86   *   &lt;s:param name="day" value="'bar'"/&gt;
87   * &lt;/s:bean&gt;
88   * <p/>
89   * &lt;table border="0" cellspacing="0" cellpadding="1"&gt;
90   * &lt;tr&gt;
91   *   &lt;th&gt;Days of the week&lt;/th&gt;
92   * &lt;/tr&gt;
93   * <p/>
94   * &lt;s:iterator value="#it.days" status="rowstatus"&gt;
95   *   &lt;tr&gt;
96   *     &lt;s:if test="#rowstatus.odd == true"&gt;
97   *       &lt;td style="background: grey"&gt;&lt;s:property/&gt;&lt;/td&gt;
98   *     &lt;/s:if&gt;
99   *     &lt;s:else&gt;
100  *       &lt;td&gt;&lt;s:property/&gt;&lt;/td&gt;
101  *     &lt;/s:else&gt;
102  *   &lt;/tr&gt;
103  * &lt;/s:iterator&gt;
104  * &lt;/table&gt;
105  *
106  * <!-- END SNIPPET: example2code -->
107  * </pre>
108  *
109  * <!--START SNIPPET: example3description -->
110  *
111  * <p> The next example will further demonstrate the use of the status attribute, using a DAO obtained from the action
112  * class through OGNL, iterating over groups and their users (in a security context). The last() method indicates if the
113  * current object is the last available in the iteration, and if not, we need to seperate the users using a comma: </p>
114  *
115  * <!-- END SNIPPET: example3description -->
116  *
117  * <pre>
118  * <!-- START SNIPPET: example3code -->
119  *
120  *  &lt;s:iterator value="groupDao.groups" status="groupStatus"&gt;
121  *      &lt;tr class="&lt;s:if test="#groupStatus.odd == true "&gt;odd&lt;/s:if&gt;&lt;s:else&gt;even&lt;/s:else&gt;"&gt;
122  *          &lt;td&gt;&lt;s:property value="name" /&gt;&lt;/td&gt;
123  *          &lt;td&gt;&lt;s:property value="description" /&gt;&lt;/td&gt;
124  *          &lt;td&gt;
125  *              &lt;s:iterator value="users" status="userStatus"&gt;
126  *                  &lt;s:property value="fullName" /&gt;&lt;s:if test="!#userStatus.last"&gt;,&lt;/s:if&gt;
127  *              &lt;/s:iterator&gt;
128  *          &lt;/td&gt;
129  *      &lt;/tr&gt;
130  *  &lt;/s:iterator&gt;
131  *
132  * <!-- END SNIPPET: example3code -->
133  * </pre>
134  * <p>
135  *
136  * <!-- START SNIPPET: example4description -->
137  *
138  * </p> The next example iterates over a an action collection and passes every iterator value to another action. The
139  * trick here lies in the use of the '[0]' operator. It takes the current iterator value and passes it on to the edit
140  * action. Using the '[0]' operator has the same effect as using &gt;s:property /&gt;. (The latter, however, does not
141  * work from inside the param tag). </p>
142  *
143  * <!-- END SNIPPET: example4description -->
144  *
145  * <pre>
146  * <!-- START SNIPPET: example4code -->
147  *
148  *      &lt;s:action name="entries" id="entries"/&gt;
149  *      &lt;s:iterator value="#entries.entries" &gt;
150  *          &lt;s:property value="name" /&gt;
151  *          &lt;s:property /&gt;
152  *          &lt;s:push value="..."&gt;
153  *              &lt;s:action name="edit" id="edit" &gt;
154  *                  &lt;s:param name="entry" value="[0]" /&gt;
155  *              &lt;/s:action&gt;
156  *          &lt;/push&gt;
157  *      &lt;/s:iterator&gt;
158  *
159  * <!-- END SNIPPET: example4code -->
160  * </pre>
161  *
162  * <!-- START SNIPPET: example5description -->
163  *
164  * </p>To simulate a simple loop with iterator tag, the following could be done.
165  * It does the loop 5 times.
166  *
167  * <!-- END SNIPPET: example5description -->
168  *
169  * <pre>
170  * <!-- START SNIPPET: example5code -->
171  *
172  * &lt;s:iterator status="stat" value="{1,2,3,4,5}" &gt;
173  *    &lt;!-- grab the index (start with 0 ... ) --&gt;
174  *    &lt;s:property value="#stat.index" /&gt;
175  *
176  *    &lt;!-- grab the top of the stack which should be the --&gt;
177  *    &lt;!-- current iteration value (0, 1, ... 5) --&gt;
178  *    &lt;s:property value="top" /&gt;
179  * &lt;/s:iterator&gt;
180  *
181  * <!-- END SNIPPET: example5code -->
182  * </pre>
183  *
184  */
185 @StrutsTag(name="iterator", tldTagClass="org.apache.struts2.views.jsp.IteratorTag", description="Iterate over a iterable value")
186 public class IteratorComponent extends Component {
187     protected Iterator iterator;
188     protected IteratorStatus status;
189     protected Object oldStatus;
190     protected IteratorStatus.StatusState statusState;
191     protected String statusAttr;
192     protected String value;
193 
194     public IteratorComponent(ValueStack stack) {
195         super(stack);
196     }
197 
198     public boolean start(Writer writer) {
199         //Create an iterator status if the status attribute was set.
200         if (statusAttr != null) {
201             statusState = new IteratorStatus.StatusState();
202             status = new IteratorStatus(statusState);
203         }
204 
205         ValueStack stack = getStack();
206 
207         if (value == null) {
208             value = "top";
209         }
210         iterator = MakeIterator.convert(findValue(value));
211 
212         // get the first
213         if ((iterator != null) && iterator.hasNext()) {
214             Object currentValue = iterator.next();
215             stack.push(currentValue);
216 
217             String id = getId();
218 
219             if ((id != null) && (currentValue != null)) {
220                 //pageContext.setAttribute(id, currentValue);
221                 //pageContext.setAttribute(id, currentValue, PageContext.REQUEST_SCOPE);
222                 stack.getContext().put(id, currentValue);
223             }
224 
225             // Status object
226             if (statusAttr != null) {
227                 statusState.setLast(!iterator.hasNext());
228                 oldStatus = stack.getContext().get(statusAttr);
229                 stack.getContext().put(statusAttr, status);
230             }
231 
232             return true;
233         } else {
234             super.end(writer, "");
235             return false;
236         }
237     }
238 
239     public boolean end(Writer writer, String body) {
240         ValueStack stack = getStack();
241         if (iterator != null) {
242             stack.pop();
243         }
244 
245         if (iterator!=null && iterator.hasNext()) {
246             Object currentValue = iterator.next();
247             stack.push(currentValue);
248 
249             String id = getId();
250 
251             if ((id != null) && (currentValue != null)) {
252                 //pageContext.setAttribute(id, currentValue);
253                 //pageContext.setAttribute(id, currentValue, PageContext.REQUEST_SCOPE);
254                 stack.getContext().put(id, currentValue);
255             }
256 
257             // Update status
258             if (status != null) {
259                 statusState.next(); // Increase counter
260                 statusState.setLast(!iterator.hasNext());
261             }
262 
263             return true;
264         } else {
265             // Reset status object in case someone else uses the same name in another iterator tag instance
266             if (status != null) {
267                 if (oldStatus == null) {
268                     stack.getContext().put(statusAttr, null);
269                 } else {
270                     stack.getContext().put(statusAttr, oldStatus);
271                 }
272             }
273             super.end(writer, "");
274             return false;
275         }
276     }
277 
278     @StrutsTagAttribute(description="If specified, an instanceof IteratorStatus will be pushed into stack upon each iteration",
279         type="Boolean", defaultValue="false")
280     public void setStatus(String status) {
281         this.statusAttr = status;
282     }
283 
284     @StrutsTagAttribute(description="the iteratable source to iterate over, else an the object itself will be put into a newly created List")
285     public void setValue(String value) {
286         this.value = value;
287     }
288 
289 }