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     <h1 id="execute-and-wait-interceptor">Execute and Wait Interceptor</h1>

 <p>The ExecuteAndWaitInterceptor is great for running long-lived actions in the background while showing the user a nice
 progress meter. This also prevents the HTTP request from timing out when the action takes more than 5 or 10 minutes.</p>

 <p>Using this interceptor is pretty straight forward. Assuming that you are including struts-default.xml, this interceptor
 is already configured but is not part of any of the default stacks. Because of the nature of this interceptor, it must
 be the <code class="highlighter-rouge">last</code> interceptor in the stack.</p>

 <p>This interceptor works on a per-session basis. That means that the same action name (<code class="highlighter-rouge">myLongRunningAction</code>, in
 the above example) cannot be run more than once at a time in a given session. On the initial request or any subsequent
 requests (before the action has completed), the <code class="highlighter-rouge">wait</code> result will be returned.</p>

 <blockquote>
   <p>The wait result is responsible for issuing a subsequent request back to the action, giving the effect
 of a self-updating progress meter.</p>
 </blockquote>

 <p>If no <code class="highlighter-rouge">wait</code> result is found, Struts will automatically generate a wait result on the fly. This result is written
 in FreeMarker and cannot run unless FreeMarker is installed. If you don’t wish to deploy with FreeMarker, you must
 provide your own wait result. This is generally a good thing to do anyway, as the default wait page is very plain.</p>

 <p>Whenever the wait result is returned, the action that is currently running in the background will be placed on top
 of the stack. This allows you to display progress data, such as a count, in the wait page. By making the wait page
 automatically reload the request to the action (which will be short-circuited by the interceptor), you can give
 the appearance of an automatic progress meter.</p>

 <p>This interceptor also supports using an initial wait delay. An initial delay is a time in milliseconds we let the server
 wait before the wait page is shown to the user. During the wait this interceptor will wake every 100 millis to check
 if the background process is done premature, thus if the job for some reason doesn’t take to long the wait page is not
 shown to the user.
 This is useful for e.g. search actions that have a wide span of execution time. Using a delay time of 2000 millis we
 ensure the user is presented fast search results immediately and for the slow results a wait page is used.</p>

 <blockquote>
   <p>Important: Because the action will be running in a separate thread, you can’t use ActionContext because it
 is a ThreadLocal. This means if you need to access, for example, session data, you need to implement <code class="highlighter-rouge">SessionAware</code>
 rather than calling <code class="highlighter-rouge">ActionContext.getSession()</code>.</p>
 </blockquote>

 <p>The thread kicked off by this interceptor will be named in the form <code class="highlighter-rouge">&lt;actionName&gt;BackgroundProcess</code>.
 For example, the <code class="highlighter-rouge">search</code> action would run as a thread named <code class="highlighter-rouge">searchBackgroundProcess</code>.</p>

 <h2 id="parameters">Parameters</h2>

 <ul>
   <li><code class="highlighter-rouge">threadPriority</code> (optional) - the priority to assign the thread. Default is <code class="highlighter-rouge">Thread.NORM_PRIORITY</code>.</li>
   <li><code class="highlighter-rouge">delay</code> (optional) - an initial delay in millis to wait before the wait page is shown (returning <code class="highlighter-rouge">wait</code> as result code).
 Default is no initial delay.</li>
   <li><code class="highlighter-rouge">delaySleepInterval</code> (optional) - only used with delay. Used for waking up at certain intervals to check if the background
 process is already done. Default is 100 millis.</li>
 </ul>

 <h2 id="extending-the-interceptor">Extending the Interceptor</h2>

 <p>If you wish to make special preparations before and/or after the invocation of the background thread, you can extend
 the <code class="highlighter-rouge">BackgroundProcess</code> class and implement the <code class="highlighter-rouge">beforeInvocation()</code> and <code class="highlighter-rouge">afterInvocation()</code> methods. This may be useful
 for  obtaining and releasing resources that the background process will need to execute successfully. To use your background
 process extension, extend <code class="highlighter-rouge">ExecuteAndWaitInterceptor</code> and implement the <code class="highlighter-rouge">getNewBackgroundProcess()</code> method.</p>

 <h2 id="examples">Examples</h2>

 <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nt">&lt;action</span> <span class="na">name=</span><span class="s">"someAction"</span> <span class="na">class=</span><span class="s">"com.examples.SomeAction"</span><span class="nt">&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"completeStack"</span><span class="nt">/&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"execAndWait"</span><span class="nt">/&gt;</span>
      <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"wait"</span><span class="nt">&gt;</span>longRunningAction-wait.jsp<span class="nt">&lt;/result&gt;</span>
      <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">&gt;</span>longRunningAction-success.jsp<span class="nt">&lt;/result&gt;</span>
  <span class="nt">&lt;/action&gt;</span>

  <span class="err">&lt;</span>%@ taglib prefix="s" uri="/struts" %&gt;
  <span class="nt">&lt;html&gt;</span>
    <span class="nt">&lt;head&gt;</span>
      <span class="nt">&lt;title&gt;</span>Please wait<span class="nt">&lt;/title&gt;</span>
      <span class="nt">&lt;meta</span> <span class="na">http-equiv=</span><span class="s">"refresh"</span> <span class="na">content=</span><span class="s">"5;url=&lt;s:url includeParams="</span><span class="err">all"</span> <span class="nt">/&gt;</span>"/&gt;
    <span class="nt">&lt;/head&gt;</span>
    <span class="nt">&lt;body&gt;</span>
      Please wait while we process your request.
      Click <span class="nt">&lt;a</span> <span class="na">href=</span><span class="s">"&lt;s:url includeParams="</span><span class="err">all"</span> <span class="nt">/&gt;</span>"&gt;<span class="nt">&lt;/a&gt;</span> if this page does not reload automatically.
    <span class="nt">&lt;/body&gt;</span>
  <span class="nt">&lt;/html&gt;</span>
  <span class="nt">&lt;/pre&gt;</span>

  <span class="nt">&lt;p&gt;&lt;u&gt;</span>Example code2:<span class="nt">&lt;/u&gt;&lt;/p&gt;</span>
  <span class="nt">&lt;p&gt;</span>
  This example will wait 2 second (2000 millis) before the wait page is shown to the user. Therefore
  if the long process didn't last long anyway the user isn't shown a wait page.
  <span class="nt">&lt;/p&gt;</span>

  <span class="nt">&lt;pre&gt;</span>
  <span class="nt">&lt;action</span> <span class="na">name=</span><span class="s">"someAction"</span> <span class="na">class=</span><span class="s">"com.examples.SomeAction"</span><span class="nt">&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"completeStack"</span><span class="nt">/&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"execAndWait"</span><span class="nt">&gt;</span>
          <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"delay"</span><span class="nt">&gt;</span>2000<span class="nt">&lt;param&gt;</span>
      <span class="nt">&lt;interceptor-ref&gt;</span>
      <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"wait"</span><span class="nt">&gt;</span>longRunningAction-wait.jsp<span class="nt">&lt;/result&gt;</span>
      <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">&gt;</span>longRunningAction-success.jsp<span class="nt">&lt;/result&gt;</span>
  <span class="nt">&lt;/action&gt;</span>
  <span class="nt">&lt;/pre&gt;</span>

  <span class="nt">&lt;p&gt;&lt;u&gt;</span>Example code3:<span class="nt">&lt;/u&gt;&lt;/p&gt;</span>
  <span class="nt">&lt;p&gt;</span>
  This example will wait 1 second (1000 millis) before the wait page is shown to the user.
  And at every 50 millis this interceptor will check if the background process is done, if so
  it will return before the 1 second has elapsed, and the user isn't shown a wait page.
  <span class="nt">&lt;/p&gt;</span>

  <span class="nt">&lt;pre&gt;</span>
  <span class="nt">&lt;action</span> <span class="na">name=</span><span class="s">"someAction"</span> <span class="na">class=</span><span class="s">"com.examples.SomeAction"</span><span class="nt">&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"completeStack"</span><span class="nt">/&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"execAndWait"</span><span class="nt">&gt;</span>
          <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"delay"</span><span class="nt">&gt;</span>1000<span class="nt">&lt;param&gt;</span>
          <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"delaySleepInterval"</span><span class="nt">&gt;</span>50<span class="nt">&lt;param&gt;</span>
      <span class="nt">&lt;interceptor-ref&gt;</span>
      <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"wait"</span><span class="nt">&gt;</span>longRunningAction-wait.jsp<span class="nt">&lt;/result&gt;</span>
      <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">&gt;</span>longRunningAction-success.jsp<span class="nt">&lt;/result&gt;</span>
  <span class="nt">&lt;/action&gt;</span>
  <span class="nt">&lt;/pre&gt;</span>

 </code></pre></div></div>

   </section>
 </article>


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	<h1 id="execute-and-wait-interceptor">Execute and Wait Interceptor</h1>

	<p>The ExecuteAndWaitInterceptor is great for running long-lived actions in the background while showing the user a nice
	progress meter. This also prevents the HTTP request from timing out when the action takes more than 5 or 10 minutes.</p>

	<p>Using this interceptor is pretty straight forward. Assuming that you are including struts-default.xml, this interceptor
	is already configured but is not part of any of the default stacks. Because of the nature of this interceptor, it must
	be the <code class="highlighter-rouge">last</code> interceptor in the stack.</p>

	<p>This interceptor works on a per-session basis. That means that the same action name (<code class="highlighter-rouge">myLongRunningAction</code>, in
	the above example) cannot be run more than once at a time in a given session. On the initial request or any subsequent
	requests (before the action has completed), the <code class="highlighter-rouge">wait</code> result will be returned.</p>

	<blockquote>
	<p>The wait result is responsible for issuing a subsequent request back to the action, giving the effect
	of a self-updating progress meter.</p>
	</blockquote>

	<p>If no <code class="highlighter-rouge">wait</code> result is found, Struts will automatically generate a wait result on the fly. This result is written
	in FreeMarker and cannot run unless FreeMarker is installed. If you don’t wish to deploy with FreeMarker, you must
	provide your own wait result. This is generally a good thing to do anyway, as the default wait page is very plain.</p>

	<p>Whenever the wait result is returned, the action that is currently running in the background will be placed on top
	of the stack. This allows you to display progress data, such as a count, in the wait page. By making the wait page
	automatically reload the request to the action (which will be short-circuited by the interceptor), you can give
	the appearance of an automatic progress meter.</p>

	<p>This interceptor also supports using an initial wait delay. An initial delay is a time in milliseconds we let the server
	wait before the wait page is shown to the user. During the wait this interceptor will wake every 100 millis to check
	if the background process is done premature, thus if the job for some reason doesn’t take to long the wait page is not
	shown to the user.
	This is useful for e.g. search actions that have a wide span of execution time. Using a delay time of 2000 millis we
	ensure the user is presented fast search results immediately and for the slow results a wait page is used.</p>

	<blockquote>
	<p>Important: Because the action will be running in a separate thread, you can’t use ActionContext because it
	is a ThreadLocal. This means if you need to access, for example, session data, you need to implement <code class="highlighter-rouge">SessionAware</code>
	rather than calling <code class="highlighter-rouge">ActionContext.getSession()</code>.</p>
	</blockquote>

	<p>The thread kicked off by this interceptor will be named in the form <code class="highlighter-rouge"><actionName>BackgroundProcess</code>.
	For example, the <code class="highlighter-rouge">search</code> action would run as a thread named <code class="highlighter-rouge">searchBackgroundProcess</code>.</p>

	<h2 id="parameters">Parameters</h2>

	<ul>
	<li><code class="highlighter-rouge">threadPriority</code> (optional) - the priority to assign the thread. Default is <code class="highlighter-rouge">Thread.NORM_PRIORITY</code>.</li>
	<li><code class="highlighter-rouge">delay</code> (optional) - an initial delay in millis to wait before the wait page is shown (returning <code class="highlighter-rouge">wait</code> as result code).
	Default is no initial delay.</li>
	<li><code class="highlighter-rouge">delaySleepInterval</code> (optional) - only used with delay. Used for waking up at certain intervals to check if the background
	process is already done. Default is 100 millis.</li>
	</ul>

	<h2 id="extending-the-interceptor">Extending the Interceptor</h2>

	<p>If you wish to make special preparations before and/or after the invocation of the background thread, you can extend
	the <code class="highlighter-rouge">BackgroundProcess</code> class and implement the <code class="highlighter-rouge">beforeInvocation()</code> and <code class="highlighter-rouge">afterInvocation()</code> methods. This may be useful
	for obtaining and releasing resources that the background process will need to execute successfully. To use your background
	process extension, extend <code class="highlighter-rouge">ExecuteAndWaitInterceptor</code> and implement the <code class="highlighter-rouge">getNewBackgroundProcess()</code> method.</p>

	<h2 id="examples">Examples</h2>

	<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nt"><action</span> <span class="na">name=</span><span class="s">"someAction"</span> <span class="na">class=</span><span class="s">"com.examples.SomeAction"</span><span class="nt">></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"completeStack"</span><span class="nt">/></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"execAndWait"</span><span class="nt">/></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"wait"</span><span class="nt">></span>longRunningAction-wait.jsp<span class="nt"></result></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">></span>longRunningAction-success.jsp<span class="nt"></result></span>
	<span class="nt"></action></span>

	<span class="err"><</span>%@ taglib prefix="s" uri="/struts" %>
	<span class="nt"><html></span>
	<span class="nt"><head></span>
	<span class="nt"><title></span>Please wait<span class="nt"></title></span>
	<span class="nt"><meta</span> <span class="na">http-equiv=</span><span class="s">"refresh"</span> <span class="na">content=</span><span class="s">"5;url=<s:url includeParams="</span><span class="err">all"</span> <span class="nt">/></span>"/>
	<span class="nt"></head></span>
	<span class="nt"><body></span>
	Please wait while we process your request.
	Click <span class="nt"><a</span> <span class="na">href=</span><span class="s">"<s:url includeParams="</span><span class="err">all"</span> <span class="nt">/></span>"><span class="nt"></a></span> if this page does not reload automatically.
	<span class="nt"></body></span>
	<span class="nt"></html></span>
	<span class="nt"></pre></span>

	<span class="nt"><p><u></span>Example code2:<span class="nt"></u></p></span>
	<span class="nt"><p></span>
	This example will wait 2 second (2000 millis) before the wait page is shown to the user. Therefore
	if the long process didn't last long anyway the user isn't shown a wait page.
	<span class="nt"></p></span>

	<span class="nt"><pre></span>
	<span class="nt"><action</span> <span class="na">name=</span><span class="s">"someAction"</span> <span class="na">class=</span><span class="s">"com.examples.SomeAction"</span><span class="nt">></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"completeStack"</span><span class="nt">/></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"execAndWait"</span><span class="nt">></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"delay"</span><span class="nt">></span>2000<span class="nt"><param></span>
	<span class="nt"><interceptor-ref></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"wait"</span><span class="nt">></span>longRunningAction-wait.jsp<span class="nt"></result></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">></span>longRunningAction-success.jsp<span class="nt"></result></span>
	<span class="nt"></action></span>
	<span class="nt"></pre></span>

	<span class="nt"><p><u></span>Example code3:<span class="nt"></u></p></span>
	<span class="nt"><p></span>
	This example will wait 1 second (1000 millis) before the wait page is shown to the user.
	And at every 50 millis this interceptor will check if the background process is done, if so
	it will return before the 1 second has elapsed, and the user isn't shown a wait page.
	<span class="nt"></p></span>

	<span class="nt"><pre></span>
	<span class="nt"><action</span> <span class="na">name=</span><span class="s">"someAction"</span> <span class="na">class=</span><span class="s">"com.examples.SomeAction"</span><span class="nt">></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"completeStack"</span><span class="nt">/></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"execAndWait"</span><span class="nt">></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"delay"</span><span class="nt">></span>1000<span class="nt"><param></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"delaySleepInterval"</span><span class="nt">></span>50<span class="nt"><param></span>
	<span class="nt"><interceptor-ref></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"wait"</span><span class="nt">></span>longRunningAction-wait.jsp<span class="nt"></result></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">></span>longRunningAction-success.jsp<span class="nt"></result></span>
	<span class="nt"></action></span>
	<span class="nt"></pre></span>

	</code></pre></div></div>

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