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| <section class="col-md-12"> |
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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="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="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="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="highlighter-rouge">session</code> - a list of action properties to be bound to session scope</li> |
| <li><code class="highlighter-rouge">application</code> - a list of action properties to be bound to application scope</li> |
| <li><code class="highlighter-rouge">key</code> - a session/application attribute key prefix, can contain following values: |
| <ul> |
| <li><code class="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="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="highlighter-rouge">type</code> - with one of the following |
| <ul> |
| <li><code class="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="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="highlighter-rouge">IllegalArgumentException</code></li> |
| </ul> |
| </li> |
| <li><code class="highlighter-rouge">sessionReset</code> - name of a parameter (defaults to <code class="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="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="highlighter-rouge">reset</code> - boolean, defaults to <code class="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="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="highlighter-rouge">getPerson()</code> getter in <code class="highlighter-rouge">ScopeActionA</code> and a <code class="highlighter-rouge">setPerson(Person person)</code> setter |
| in <code class="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> |
| </article> |
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