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Struts 2
Iteration Tags
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Added by tjsnell, last edited by Ted Husted on Sep 02, 2006 (view change)

- iterator
- generator
- append
- subset
- merge
- sort

Iterator will iterate over a value. An iterable value can be either of: java.util.Collection, java.util.Iterator, java.util.Enumeration, java.util.Map, array.

Example:

    <ww:iterator value="days">
       <p>day is: <ww:property/></p>
     </ww:iterator>

The above example retrieves the value of the getDays() method of the current object on the value stack and uses it to iterate over. The <ww:property/> tag prints out the current value of the iterator.

The following example uses a BeanTag and places it into the ActionContext. The iterator tag will retrieve that object from the ActionContext and then calls its getDays() method as above. The status attribute is also used to create a IteratorStatus object, which in this example, its odd() method is used to alternate row colours:

    <ww:bean name="com.opensymphony.webwork.example.IteratorExample" id="it">
       <ww:param name="day" value="'foo'"/>
       <ww:param name="day" value="'bar'"/>
     </ww:bean>

     <table border="0" cellspacing="0" cellpadding="1">
     <tr>
       <th>Days of the week</th>
     </tr>

     <ww:iterator value="#it.days" status="rowstatus">
       <tr>
         <ww:if test="#rowstatus.odd == true">
           <td style="background: grey"><ww:property/></td>
         </ww:if>
         <ww:else>
           <td><ww:property/></td>
         </ww:else>
       </tr>
     </ww:iterator>
     </table>

The next example will further demonstrate the use of the status attribute, using a DAO obtained from the action class through OGNL, iterating over groups and their users (in a security context). The last() method indicates if the current object is the last available in the iteration, and if not, we need to seperate the users using a comma:

    <webwork:iterator value="groupDao.groups" status="groupStatus">
        <tr class="<webwork:if test="#groupStatus.odd == true ">odd</webwork:if><webwork:else>even</webwork:else>">
            <td><webwork:property value="name" /></td>
            <td><webwork:property value="description" /></td>
            <td>
                <webwork:iterator value="users" status="userStatus">
                    <webwork:property value="fullName" /><webwork:if test="!#userStatus.last">,</webwork:if>
                </webwork:iterator>
            </td>
        </tr>
    </webwork:iterator>

The next example iterates over a an action collection and passes every iterator value to another action.

    <ww:action name="entries" id="entries"/>
    <ww:iterator value="#entries.entries" >
       <ww:property value="name" />
       <ww:property />
       <ww:push value="..."/>

       <ww:action name="edit" id="edit" >
         <ww:param name="entry" value="[0]" />
       </ww:action>
    </ww:iterator>

The trick here lies in the use of the '[:0]' operator. It takes the current iterator value and passes it on to the edit action. Using the '[:0]' operator has the same effect as using <ww:property />. (The latter, however, does not work from inside the param tag).
See also [OS:WebWork2 EL].