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<a class="edit-on-gh" href="https://github.com/apache/struts-site/edit/master/source/tag-developers/merge-tag.md" title="Edit this page on GitHub">Edit on GitHub</a>
<a href="tag-reference.html" title="back to Tag Reference"><< back to Tag Reference</a>
<h1 id="merge">merge</h1>
<p>Please make sure you have read the <a href="tag-syntax">Tag Syntax</a> document and understand how tag attribute syntax works.</p>
<h2 id="description">Description</h2>
<p>Component for MergeIteratorTag, which job is to merge iterators and successive call to the merged iterator will cause
each merge iterator to have a chance to expose its element, subsequently next call will allow the next iterator to expose
its element. Once the last iterator is done exposing its element, the first iterator is allowed to do so again (unless
it is exhausted of entries).</p>
<p>Internally the task are delegated to <code class="highlighter-rouge">MergeIteratorFilter</code>.</p>
<p>Example if there are 3 lists being merged, each list have 3 entries, the following will be the logic.</p>
<ol>
<li>Display first element of the first list</li>
<li>Display first element of the second list</li>
<li>Display first element of the third list</li>
<li>Display second element of the first list&lt;</li>
<li>Display second element of the second list</li>
<li>Display second element of the third list</li>
<li>Display third element of the first list&lt;</li>
<li>Display third element of the second list</li>
<li>Display third element of the third list</li>
</ol>
<p>Merge the values of a list of iterators into one iterator</p>
<h2 id="attributes">Attributes</h2>
<table width="100%">
<tr>
<td colspan="6"><h4>Dynamic Attributes Allowed:</h4> false</td>
</tr>
<tr>
<td colspan="6">&nbsp;</td>
</tr>
<tr>
<th align="left" valign="top"><h4>Name</h4></th>
<th align="left" valign="top"><h4>Required</h4></th>
<th align="left" valign="top"><h4>Default</h4></th>
<th align="left" valign="top"><h4>Evaluated</h4></th>
<th align="left" valign="top"><h4>Type</h4></th>
<th align="left" valign="top"><h4>Description</h4></th>
</tr>
<tr>
<td align="left" valign="top">var</td>
<td align="left" valign="top">false</td>
<td align="left" valign="top"></td>
<td align="left" valign="top">false</td>
<td align="left" valign="top">String</td>
<td align="left" valign="top">The name where the resultant merged iterator will be stored in the stack's context</td>
</tr>
</table>
<h2 id="examples">Examples</h2>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">public</span> <span class="kd">class</span> <span class="nc">MergeIteratorTagAction</span> <span class="kd">extends</span> <span class="n">ActionSupport</span> <span class="o">{</span>
<span class="kd">private</span> <span class="n">List</span> <span class="n">myList1</span><span class="o">;</span>
<span class="kd">private</span> <span class="n">List</span> <span class="n">myList2</span><span class="o">;</span>
<span class="kd">private</span> <span class="n">List</span> <span class="n">myList3</span><span class="o">;</span>
<span class="kd">public</span> <span class="n">List</span> <span class="nf">getMyList1</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">myList1</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="n">List</span> <span class="nf">getMyList2</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">myList2</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="n">List</span> <span class="nf">getMyList3</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">myList3</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="n">String</span> <span class="nf">execute</span><span class="o">()</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span>
<span class="n">myList1</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayList</span><span class="o">();</span>
<span class="n">myList1</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"1"</span><span class="o">);</span>
<span class="n">myList1</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"2"</span><span class="o">);</span>
<span class="n">myList1</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"3"</span><span class="o">);</span>
<span class="n">myList2</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayList</span><span class="o">();</span>
<span class="n">myList2</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"a"</span><span class="o">);</span>
<span class="n">myList2</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"b"</span><span class="o">);</span>
<span class="n">myList2</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"c"</span><span class="o">);</span>
<span class="n">myList3</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayList</span><span class="o">();</span>
<span class="n">myList3</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"A"</span><span class="o">);</span>
<span class="n">myList3</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"B"</span><span class="o">);</span>
<span class="n">myList3</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="s">"C"</span><span class="o">);</span>
<span class="k">return</span> <span class="s">"done"</span><span class="o">;</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<pre><code class="language-jsp">&lt;s:merge var="myMergedIterator1"&gt;
&lt;s:param value="%{myList1}" /&gt;
&lt;s:param value="%{myList2}" /&gt;
&lt;s:param value="%{myList3}" /&gt;
&lt;/s:merge&gt;
&lt;s:iterator value="%{#myMergedIterator1}"&gt;
&lt;s:property /&gt;
&lt;/s:iterator&gt;
</code></pre>
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