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<h1 id="model-driven">Model Driven</h1>
<p>Struts 2 does not have “forms” like Struts 1 did. In Struts 2 request parameters are bound directly to fields in the actions class, and this class is placed on top of the stack when the action is executed.</p>
<p>If an action class implements the interface <code class="language-plaintext highlighter-rouge">com.opensymphony.xwork2.ModelDriven</code> then it needs to return an object from the <code class="language-plaintext highlighter-rouge">getModel()</code> method. Struts will then populate the fields of this object with the request parameters, and this object will be placed on top of the stack once the action is executed. Validation will also be performed on this model object, instead of the action. Please read about <a href="visitor-field-validator-annotation">VisitorFieldValidator Annotation</a> which can help you validate model’s fields.</p>
<h2 id="interceptor">Interceptor</h2>
<p>To use <code class="language-plaintext highlighter-rouge">ModelDriven</code> actions, make sure that the <a href="model-driven-interceptor">Model Driven Interceptor</a> is applied to your action. This interceptor is part of the default interceptor stack <code class="language-plaintext highlighter-rouge">defaultStack</code> so it is applied to all actions by default.</p>
<h2 id="example">Example</h2>
<p>Action class:</p>
<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">ModelDrivenAction</span> <span class="kd">implements</span> <span class="nc">ModelDriven</span> <span class="o">{</span>
<span class="kd">public</span> <span class="nc">String</span> <span class="nf">execute</span><span class="o">()</span> <span class="kd">throws</span> <span class="nc">Exception</span> <span class="o">{</span>
<span class="k">return</span> <span class="no">SUCCESS</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="nc">Object</span> <span class="nf">getModel</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="k">new</span> <span class="nf">Gangster</span><span class="o">();</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<p>Gangster class (model):</p>
<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">Gangster</span> <span class="kd">implements</span> <span class="nc">Serializable</span> <span class="o">{</span>
<span class="kd">private</span> <span class="nc">String</span> <span class="n">name</span><span class="o">;</span>
<span class="kd">private</span> <span class="kt">int</span> <span class="n">age</span><span class="o">;</span>
<span class="kd">private</span> <span class="nc">String</span> <span class="n">description</span><span class="o">;</span>
<span class="kd">private</span> <span class="kt">boolean</span> <span class="n">bustedBefore</span><span class="o">;</span>
<span class="kd">public</span> <span class="kt">int</span> <span class="nf">getAge</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">age</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">setAge</span><span class="o">(</span><span class="kt">int</span> <span class="n">age</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">age</span> <span class="o">=</span> <span class="n">age</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kt">boolean</span> <span class="nf">isBustedBefore</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">bustedBefore</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">setBustedBefore</span><span class="o">(</span><span class="kt">boolean</span> <span class="n">bustedBefore</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">bustedBefore</span> <span class="o">=</span> <span class="n">bustedBefore</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="nc">String</span> <span class="nf">getDescription</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">description</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">setDescription</span><span class="o">(</span><span class="nc">String</span> <span class="n">description</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">description</span> <span class="o">=</span> <span class="n">description</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="nc">String</span> <span class="nf">getName</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">name</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">setName</span><span class="o">(</span><span class="nc">String</span> <span class="n">name</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">name</span> <span class="o">=</span> <span class="n">name</span><span class="o">;</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<p>JSP for creating a Gangster:</p>
<div class="language-jsp highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt">&lt;s:form </span><span class="na">action=</span><span class="s">"modelDrivenResult"</span><span class="na"> method=</span><span class="s">"POST"</span><span class="na"> namespace=</span><span class="s">"/modelDriven"</span><span class="nt">&gt;</span>
<span class="nt">&lt;s:textfield </span><span class="na">label=</span><span class="s">"Gangster Name"</span><span class="na"> name=</span><span class="s">"name"</span> <span class="nt">/&gt;</span>
<span class="nt">&lt;s:textfield </span><span class="na">label=</span><span class="s">"Gangster Age"</span><span class="na"> name=</span><span class="s">"age"</span> <span class="nt">/&gt;</span>
<span class="nt">&lt;s:checkbox </span><span class="na">label=</span><span class="s">"Gangster Busted Before"</span><span class="na"> name=</span><span class="s">"bustedBefore"</span> <span class="nt">/&gt;</span>
<span class="nt">&lt;s:textarea </span><span class="na">cols=</span><span class="s">"30"</span><span class="na"> rows=</span><span class="s">"5"</span><span class="na"> label=</span><span class="s">"Gangster Description"</span><span class="na"> name=</span><span class="s">"description"</span> <span class="nt">/&gt;</span>
<span class="nt">&lt;s:submit /&gt;</span>
<span class="nt">&lt;/s:form&gt;</span>
</code></pre></div></div>
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