Struts 2 Control Tags

最新推荐文章于 2022-01-24 21:54:04 发布

转载最新推荐文章于 2022-01-24 21:54:04 发布 · 533 阅读

文章标签：

#struts #tags #iterator #generator #parameters #merge

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本文详细介绍了 Struts2 框架中用于页面流程控制的重要标签，包括条件判断标签 if/else 和迭代标签 iterator 的使用方法。此外还讲解了如何通过 merge 和 append 标签合并列表，以及如何利用 generator 标签生成迭代器。

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>

Check Detailed Example

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>

Check Detailed Example

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>

Check Detailed Example

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>

Check Detailed Example

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>

Check Detailed Example