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     <a href="interceptors.html" title="back to Interceptors"><< back to Interceptors</a>

     <h1 id="scope-interceptor">Scope Interceptor</h1>

 <p>This is designed to solve a few simple issues related to wizard-like functionality in Struts. One of those issues is that
 some applications have a application-wide parameters commonly used, such <code class="language-plaintext highlighter-rouge">pageLen</code> (used for records per page). Rather
 than requiring that each action check if such parameters are supplied, this interceptor can look for specified parameters
 and pull them out of the session.</p>

 <p>This works by setting listed properties at action start with values from session/application attributes keyed after
 the action’s class, the action’s name, or any supplied key. After action is executed all the listed properties are taken
 back and put in session or application context.</p>

 <p>To make sure that each execution of the action is consistent it makes use of session-level locking. This way it guarantees
 that each action execution is atomic at the session level. It doesn’t guarantee application level consistency however
 there has yet to be enough reasons to do so. Application level consistency would also be a big performance overkill.</p>

 <p>Note that this interceptor takes a snapshot of action properties just before result is presented (using a <code class="language-plaintext highlighter-rouge">PreResultListener</code>),
 rather than after action is invoked. There is a reason for that: At this moment we know that action’s state is <code class="language-plaintext highlighter-rouge">complete</code>
 as its values may depend on the rest of the stack and specifically - on the values of nested interceptors.</p>

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

 <ul>
   <li><code class="language-plaintext highlighter-rouge">session</code> - a list of action properties to be bound to session scope</li>
   <li><code class="language-plaintext highlighter-rouge">application</code> - a list of action properties to be bound to application scope</li>
   <li><code class="language-plaintext highlighter-rouge">key</code> - a session/application attribute key prefix, can contain following values:
     <ul>
       <li><code class="language-plaintext highlighter-rouge">CLASS</code> - that creates a unique key prefix based on action namespace and action class, it’s a default value</li>
       <li><code class="language-plaintext highlighter-rouge">ACTION</code> - creates a unique key prefix based on action namespace and action name</li>
       <li>any other value is taken literally as key prefix</li>
     </ul>
   </li>
   <li><code class="language-plaintext highlighter-rouge">type</code> - with one of the following
     <ul>
       <li><code class="language-plaintext highlighter-rouge">start</code> - means it’s a start action of the wizard-like action sequence and all session scoped properties are reset
 to their defaults</li>
       <li><code class="language-plaintext highlighter-rouge">end</code> - means that session scoped properties are removed from session after action is run</li>
       <li>any other value throws <code class="language-plaintext highlighter-rouge">IllegalArgumentException</code></li>
     </ul>
   </li>
   <li><code class="language-plaintext highlighter-rouge">sessionReset</code> - name of a parameter (defaults to <code class="language-plaintext highlighter-rouge">session.reset</code>) which if set, causes all session values to be
 reset to action’s default values or application scope values, note that it is similar to <code class="language-plaintext highlighter-rouge">type="start"</code> and in fact
 it does the same, but in our team it is sometimes semantically preferred. We use session scope in two patterns -
 sometimes there are wizard-like action sequences that have start and end, and sometimes we just want simply reset
 current session values.</li>
   <li><code class="language-plaintext highlighter-rouge">reset</code> - boolean, defaults to <code class="language-plaintext highlighter-rouge">false</code>, if set, it has the same effect as setting all session values to be reset
 to action’s default values or application.</li>
   <li><code class="language-plaintext highlighter-rouge">autoCreateSession</code> - boolean value, sets if the session should be automatically created.</li>
 </ul>

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

 <p>There are no know extension points for this interceptor.</p>

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

 <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="c">&lt;!-- As the filter and orderBy parameters are common for all my browse-type actions,
       you can move control to the scope interceptor. In the session parameter you can list
       action properties that are going to be automatically managed over session. You can
       do the same for application-scoped variables--&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">"basicStack"</span><span class="nt">/&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"hibernate"</span><span class="nt">/&gt;</span>
      <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"scope"</span><span class="nt">&gt;</span>
          <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"session"</span><span class="nt">&gt;</span>filter,orderBy<span class="nt">&lt;/param&gt;</span>
          <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"autoCreateSession"</span><span class="nt">&gt;</span>true<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">"success"</span><span class="nt">&gt;</span>good_result.ftl<span class="nt">&lt;/result&gt;</span>
  <span class="nt">&lt;/action&gt;</span>

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

 <p><strong>Some more examples</strong></p>

 <p>The scope interceptor can be used to pass arbitrary objects from one action ActionA to another other ActionB, provided
 you have a getter in ActionA and and a similar setter in actionB. Also, you should use a key parameter to make sure you
 tell ASF/WW which action gets which objects. This allows you to mix several actions with several scopes, without running
 the risk of getting wrong objects.</p>

 <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">"scopea"</span> <span class="na">class=</span><span class="s">"com.mevipro.test.action.ScopeActionA"</span><span class="nt">&gt;</span>
     <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"success"</span> <span class="na">type=</span><span class="s">"dispatcher"</span><span class="nt">&gt;</span>/jsp/test.jsp<span class="nt">&lt;/result&gt;</span>
     <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"basicStack"</span><span class="nt">/&gt;</span>
     <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"scope"</span><span class="nt">&gt;</span>
         <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"key"</span><span class="nt">&gt;</span>funky<span class="nt">&lt;/param&gt;</span>
         <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"session"</span><span class="nt">&gt;</span>person<span class="nt">&lt;/param&gt;</span>
         <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"autoCreateSession"</span><span class="nt">&gt;</span>true<span class="nt">&lt;/param&gt;</span>
     <span class="nt">&lt;/interceptor-ref&gt;</span>
 <span class="nt">&lt;/action&gt;</span>
 <span class="nt">&lt;action</span> <span class="na">name=</span><span class="s">"scopeb"</span> <span class="na">class=</span><span class="s">"com.mevipro.test.action.ScopeActionB"</span><span class="nt">&gt;</span>
     <span class="nt">&lt;result</span> <span class="na">name=</span><span class="s">"success"</span> <span class="na">type=</span><span class="s">"dispatcher"</span><span class="nt">&gt;</span>/jsp/test.jsp<span class="nt">&lt;/result&gt;</span>
     <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"scope"</span><span class="nt">&gt;</span>
         <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"key"</span><span class="nt">&gt;</span>funky<span class="nt">&lt;/param&gt;</span>
         <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"session"</span><span class="nt">&gt;</span>person<span class="nt">&lt;/param&gt;</span>
         <span class="nt">&lt;param</span> <span class="na">name=</span><span class="s">"autoCreateSession"</span><span class="nt">&gt;</span>true<span class="nt">&lt;/param&gt;</span>
     <span class="nt">&lt;/interceptor-ref&gt;</span>
     <span class="nt">&lt;interceptor-ref</span> <span class="na">name=</span><span class="s">"basicStack"</span><span class="nt">/&gt;</span>
 <span class="nt">&lt;/action&gt;</span>
 </code></pre></div></div>

 <p>Don’t forget: you’ll need at least a <code class="language-plaintext highlighter-rouge">getPerson()</code> getter in <code class="language-plaintext highlighter-rouge">ScopeActionA</code> and a <code class="language-plaintext highlighter-rouge">setPerson(Person person)</code> setter
 in <code class="language-plaintext highlighter-rouge">ScopeActionB</code> and you need to make sure you specify the key (you don’t need this if you only use one action, as in
 the example above). Without the key, the scope interceptor will store your variables, but won’t set them on the other action.</p>

   </section>
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	<a class="edit-on-gh" href="https://github.com/apache/struts-site/edit/master/source/core-developers/scope-interceptor.md" title="Edit this page on GitHub">Edit on GitHub</a>

	<a href="interceptors.html" title="back to Interceptors"><< back to Interceptors</a>

	<h1 id="scope-interceptor">Scope Interceptor</h1>

	<p>This is designed to solve a few simple issues related to wizard-like functionality in Struts. One of those issues is that
	some applications have a application-wide parameters commonly used, such <code class="language-plaintext highlighter-rouge">pageLen</code> (used for records per page). Rather
	than requiring that each action check if such parameters are supplied, this interceptor can look for specified parameters
	and pull them out of the session.</p>

	<p>This works by setting listed properties at action start with values from session/application attributes keyed after
	the action’s class, the action’s name, or any supplied key. After action is executed all the listed properties are taken
	back and put in session or application context.</p>

	<p>To make sure that each execution of the action is consistent it makes use of session-level locking. This way it guarantees
	that each action execution is atomic at the session level. It doesn’t guarantee application level consistency however
	there has yet to be enough reasons to do so. Application level consistency would also be a big performance overkill.</p>

	<p>Note that this interceptor takes a snapshot of action properties just before result is presented (using a <code class="language-plaintext highlighter-rouge">PreResultListener</code>),
	rather than after action is invoked. There is a reason for that: At this moment we know that action’s state is <code class="language-plaintext highlighter-rouge">complete</code>
	as its values may depend on the rest of the stack and specifically - on the values of nested interceptors.</p>

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

	<ul>
	<li><code class="language-plaintext highlighter-rouge">session</code> - a list of action properties to be bound to session scope</li>
	<li><code class="language-plaintext highlighter-rouge">application</code> - a list of action properties to be bound to application scope</li>
	<li><code class="language-plaintext highlighter-rouge">key</code> - a session/application attribute key prefix, can contain following values:
	<ul>
	<li><code class="language-plaintext highlighter-rouge">CLASS</code> - that creates a unique key prefix based on action namespace and action class, it’s a default value</li>
	<li><code class="language-plaintext highlighter-rouge">ACTION</code> - creates a unique key prefix based on action namespace and action name</li>
	<li>any other value is taken literally as key prefix</li>
	</ul>
	</li>
	<li><code class="language-plaintext highlighter-rouge">type</code> - with one of the following
	<ul>
	<li><code class="language-plaintext highlighter-rouge">start</code> - means it’s a start action of the wizard-like action sequence and all session scoped properties are reset
	to their defaults</li>
	<li><code class="language-plaintext highlighter-rouge">end</code> - means that session scoped properties are removed from session after action is run</li>
	<li>any other value throws <code class="language-plaintext highlighter-rouge">IllegalArgumentException</code></li>
	</ul>
	</li>
	<li><code class="language-plaintext highlighter-rouge">sessionReset</code> - name of a parameter (defaults to <code class="language-plaintext highlighter-rouge">session.reset</code>) which if set, causes all session values to be
	reset to action’s default values or application scope values, note that it is similar to <code class="language-plaintext highlighter-rouge">type="start"</code> and in fact
	it does the same, but in our team it is sometimes semantically preferred. We use session scope in two patterns -
	sometimes there are wizard-like action sequences that have start and end, and sometimes we just want simply reset
	current session values.</li>
	<li><code class="language-plaintext highlighter-rouge">reset</code> - boolean, defaults to <code class="language-plaintext highlighter-rouge">false</code>, if set, it has the same effect as setting all session values to be reset
	to action’s default values or application.</li>
	<li><code class="language-plaintext highlighter-rouge">autoCreateSession</code> - boolean value, sets if the session should be automatically created.</li>
	</ul>

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

	<p>There are no know extension points for this interceptor.</p>

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

	<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="c"><!-- As the filter and orderBy parameters are common for all my browse-type actions,
	you can move control to the scope interceptor. In the session parameter you can list
	action properties that are going to be automatically managed over session. You can
	do the same for application-scoped variables--></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">"basicStack"</span><span class="nt">/></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"hibernate"</span><span class="nt">/></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"scope"</span><span class="nt">></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"session"</span><span class="nt">></span>filter,orderBy<span class="nt"></param></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"autoCreateSession"</span><span class="nt">></span>true<span class="nt"></param></span>
	<span class="nt"></interceptor-ref></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">></span>good_result.ftl<span class="nt"></result></span>
	<span class="nt"></action></span>

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

	<p><strong>Some more examples</strong></p>

	<p>The scope interceptor can be used to pass arbitrary objects from one action ActionA to another other ActionB, provided
	you have a getter in ActionA and and a similar setter in actionB. Also, you should use a key parameter to make sure you
	tell ASF/WW which action gets which objects. This allows you to mix several actions with several scopes, without running
	the risk of getting wrong objects.</p>

	<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">"scopea"</span> <span class="na">class=</span><span class="s">"com.mevipro.test.action.ScopeActionA"</span><span class="nt">></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span> <span class="na">type=</span><span class="s">"dispatcher"</span><span class="nt">></span>/jsp/test.jsp<span class="nt"></result></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"basicStack"</span><span class="nt">/></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"scope"</span><span class="nt">></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"key"</span><span class="nt">></span>funky<span class="nt"></param></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"session"</span><span class="nt">></span>person<span class="nt"></param></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"autoCreateSession"</span><span class="nt">></span>true<span class="nt"></param></span>
	<span class="nt"></interceptor-ref></span>
	<span class="nt"></action></span>
	<span class="nt"><action</span> <span class="na">name=</span><span class="s">"scopeb"</span> <span class="na">class=</span><span class="s">"com.mevipro.test.action.ScopeActionB"</span><span class="nt">></span>
	<span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span> <span class="na">type=</span><span class="s">"dispatcher"</span><span class="nt">></span>/jsp/test.jsp<span class="nt"></result></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"scope"</span><span class="nt">></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"key"</span><span class="nt">></span>funky<span class="nt"></param></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"session"</span><span class="nt">></span>person<span class="nt"></param></span>
	<span class="nt"><param</span> <span class="na">name=</span><span class="s">"autoCreateSession"</span><span class="nt">></span>true<span class="nt"></param></span>
	<span class="nt"></interceptor-ref></span>
	<span class="nt"><interceptor-ref</span> <span class="na">name=</span><span class="s">"basicStack"</span><span class="nt">/></span>
	<span class="nt"></action></span>
	</code></pre></div></div>

	<p>Don’t forget: you’ll need at least a <code class="language-plaintext highlighter-rouge">getPerson()</code> getter in <code class="language-plaintext highlighter-rouge">ScopeActionA</code> and a <code class="language-plaintext highlighter-rouge">setPerson(Person person)</code> setter
	in <code class="language-plaintext highlighter-rouge">ScopeActionB</code> and you need to make sure you specify the key (you don’t need this if you only use one action, as in
	the example above). Without the key, the scope interceptor will store your variables, but won’t set them on the other action.</p>

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