Struts 2 - Control Tags

The Struts 2 tags have a set of tags that make it easy to control the flow of page execution. Following is the list of important Struts 2 Control Tags:

The if and else tags

These tags perform basic condition flow found in every language. 'If' tag could be used by itself or with 'Else If' Tag and/or single/multiple 'Else' Tag as shown below:

<s:if test="%{false}">
    <div>Will Not Be Executed</div>
</s:if>
<s:elseif test="%{true}">
    <div>Will Be Executed</div>
</s:elseif>
<s:else>
    <div>Will Not Be Executed</div>
</s:else>

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The iterator tags

These iterator will iterate over a value. An iterable value can be any of: java.util.Collection, java.util.Iterator. While iterating over an iterator, you can use Sort tag to sort the result or SubSet tag to to get a sub set of the list or array.
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>

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The merge tag

These merge tag take two or more lists as parameters and merge them all together as shown below:

<s:merge var="myMergedIterator">
     <s:param value="%{myList1}" />
     <s:param value="%{myList2}" />
     <s:param value="%{myList3}" />
</s:merge>
<s:iterator value="%{#myMergedIterator}">
     <s:property />
</s:iterator>

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The append tag

These append tag take two or more lists as parameters and append them all together as shown below:

<s:append var="myAppendIterator">
     <s:param value="%{myList1}" />
     <s:param value="%{myList2}" />
     <s:param value="%{myList3}" />
</s:append>
<s:iterator value="%{#myAppendIterator}">
     <s:property />
</s:iterator>

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The generator tag

These generator tag generates an iterator based on the val attribute supplied. Following generator tag generates an iterator and print it out using the iterator tag.

<s:generator val="%{'aaa,bbb,ccc,ddd,eee'}">
 <s:iterator>
     <s:property /><br/>
 </s:iterator>
</s:generator>

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