iterator

• Description
• Attributes
• Conversion
• Examples

Please make sure you have read the Tag Syntax document and understand how tag attribute syntax works.

NOTE: The id attribute is deprecated in Struts 2.1.x, and has been replaced by the var attribute. The begin, end and step attributes are only available from 2.1.7+

Description

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

Iterate over a iterable value

Attributes

Conversion

Values generated by the tag are subject of internal conversion mechanism. It means when generating ordinary numbers and then using them with <s:property/>, the Integers will be converted to Strings using the current locale. This can impact how the numbers are presented. Since Struts 6.4.0 to avoid conversion you can use the status object and its countStr and indexStr which are a String representation of the numbers. The following example demonstrates the case when using fa_IR locale:

<s:iterator begin="1" end="3" status="status">
    <s:property/>
    <s:textfield id="text_%{#status.countStr}" name="test[%{#status.indexStr}]"/>
</s:iterator>

۰
<input type="text" name="test[0]" value="" id="text_1">
۱
<input type="text" name="test[1]" value="" id="text_2">
۲
<input type="text" name="test[2]" value="" id="text_3">

Examples

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

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

The following example uses a Bean tag 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 an IteratorStatus object, which in this example, its odd() method is used to alternate row colours:

<s:bean name="org.apache.struts2.example.IteratorExample" var="it">
  <s:param name="day" value="'foo'"/>
  <s:param name="day" value="'bar'"/>
</s:bean>

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

<s:iterator value="#it.days" status="rowstatus">
  <tr>
    <s:if test="#rowstatus.odd == true">
      <td style="background: grey"><s:property/></td>
    </s:if>
    <s:else>
      <td><s:property/></td>
    </s:else>
  </tr>
</s: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 separate the users using a comma:

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

The next example iterates over a an action collection and passes every iterator value to another action. 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 <s:property />. (The latter, however, does not work from inside the param tag).

<s:action name="entries" var="entries"/>
<s:iterator value="#entries.entries" >
    <s:property value="name" />
    <s:property />
    <s:push value="...">
        <s:action name="edit" var="edit" >
            <s:param name="entry" value="[0]" />
        </s:action>
    </push>
</s:iterator>

A loop that iterates 5 times

<s:iterator var="counter" begin="1" end="5" >
   <!-- current iteration value (1, ... 5) -->
   <s:property value="top" />
</s:iterator>

Another way to create a simple loop, similar to JSTL’s <c:forEach begin="..." end="..." ...> is to use some OGNL magic, which provides some under-the-covers magic to make 0-n loops trivial. This example also loops five times.

<s:iterator status="stat" value="(5).{ #this }" >
   <s:property value="#stat.count" /> <!-- Note that "count" is 1-based, "index" is 0-based. -->
</s:iterator>

A loop that iterates over a partial list

<s:iterator value="{1,2,3,4,5}" begin="2" end="4" >
   <!-- current iteration value (2,3,4) -->
   <s:property value="top" />
</s:iterator>

Another example when we can access a variable out of the current loop context and where name clashes with the current

<s:select name="location" size="1" list="locations" listKey="key"
  listValue="value" emptyOption="false" />

<s:iterator var="item" value="items" status="rowstatus">
    <s:url var="myUrl" action="itemDelete">
        <s:param name="id" value="#item.id" />
        <%-- Outer loop variable name [1]. as clash with item.location --%>
        <s:param name="location" value="[1].location" />
    </s:url>
</s:iterator>