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| <a class="edit-on-gh" href="https://github.com/apache/struts-site/edit/master/source/getting-started/coding-actions.md" title="Edit this page on GitHub">Edit on GitHub</a> |
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| <a href="index.html" title="back to Getting started"><< back to Getting started</a> |
| |
| <h1 class="no_toc" id="coding-actions">Coding actions</h1> |
| |
| <ul id="markdown-toc"> |
| <li><a href="#introduction" id="markdown-toc-introduction">Introduction</a></li> |
| <li><a href="#struts-2-action-classes" id="markdown-toc-struts-2-action-classes">Struts 2 Action Classes</a></li> |
| <li><a href="#processing-form-input-in-the-action-class" id="markdown-toc-processing-form-input-in-the-action-class">Processing Form Input In The Action Class</a></li> |
| <li><a href="#summary" id="markdown-toc-summary">Summary</a></li> |
| </ul> |
| |
| <p>This tutorial assumes you’ve completed the <a href="using-tags">Using Struts 2 Tags</a> tutorial and have a working <strong>using-tags</strong> |
| project. The example code for this tutorial, <strong>coding-actions</strong>, is available for checkout from the Struts 2 GitHub repository |
| <a href="https://github.com/apache/struts-examples">struts-examples</a>.</p> |
| |
| <h2 id="introduction">Introduction</h2> |
| |
| <p>Coding a Struts 2 Action involves several parts:</p> |
| |
| <ol> |
| <li>Mapping an action to a class</li> |
| <li>Mapping a result to a view</li> |
| <li>Writing the controller logic in the Action class</li> |
| </ol> |
| |
| <p>In the previous tutorials we covered how to configure Struts to map a URL such as <code class="language-plaintext highlighter-rouge">hello.action</code> to an Action class |
| such as <code class="language-plaintext highlighter-rouge">HelloWorldAction</code> (specifically the execute method).</p> |
| |
| <p><strong>Action Mapping</strong></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">"hello"</span> <span class="na">class=</span><span class="s">"org.apache.struts.helloworld.action.HelloWorldAction"</span> <span class="na">method=</span><span class="s">"execute"</span><span class="nt">></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"success"</span><span class="nt">></span>/HelloWorld.jsp<span class="nt"></result></span> |
| <span class="nt"></action></span> |
| </code></pre></div></div> |
| |
| <p>The Action mapping above also specified that if the <code class="language-plaintext highlighter-rouge">execute</code> method of class <code class="language-plaintext highlighter-rouge">HelloWorldAction</code> returns <code class="language-plaintext highlighter-rouge">success</code> |
| then the view <code class="language-plaintext highlighter-rouge">HelloWorld.jsp</code> will be returned to the browser.</p> |
| |
| <p>This tutorial will introduce you to the basics of writing the controller logic in the Action class.</p> |
| |
| <h2 id="struts-2-action-classes">Struts 2 Action Classes</h2> |
| |
| <p>Action classes act as the controller in the MVC pattern. Action classes respond to a user action, execute business |
| logic (or call upon other classes to do that), and then return a result that tells Struts what view to render.</p> |
| |
| <p>Struts 2 Action classes usually extend the <code class="language-plaintext highlighter-rouge">ActionSupport</code> class, which is provided by the Struts 2 framework. |
| Class <code class="language-plaintext highlighter-rouge">ActionSupport</code> provides default implementations for the most common actions (e.g. execute, input) and also |
| implements several useful Struts 2 interfaces. When your Action class extends class <code class="language-plaintext highlighter-rouge">ActionSupport</code> your class can either |
| override the default implementations or inherit them.</p> |
| |
| <p>If you examine class HelloWorldAction from tutorial <a href="using-tags">Using Struts 2 Tags</a> you’ll see that it extends |
| the class <code class="language-plaintext highlighter-rouge">ActionSupport</code> and then overrides method <code class="language-plaintext highlighter-rouge">execute</code>.</p> |
| |
| <p>The method <code class="language-plaintext highlighter-rouge">execute</code> is where we placed what we want this controller to do in response to the <code class="language-plaintext highlighter-rouge">hello.action</code>.</p> |
| |
| <p><strong>Method execute of HelloWorldAction</strong></p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><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="n">messageStore</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">MessageStore</span><span class="o">()</span> <span class="o">;</span> |
| |
| <span class="n">helloCount</span><span class="o">++;</span> |
| |
| <span class="k">return</span> <span class="no">SUCCESS</span><span class="o">;</span> |
| <span class="o">}</span> |
| </code></pre></div></div> |
| <blockquote> |
| <p>Note that method execute declares it throws an Exception. We’ll cover in a later tutorial how to configure Struts |
| to handle any Exceptions thrown from the Action classes methods.</p> |
| </blockquote> |
| |
| <h2 id="processing-form-input-in-the-action-class">Processing Form Input In The Action Class</h2> |
| |
| <p>One of the most common responsibilities of the Action class is to process user input on a form and then make |
| the result of the processing available to the view page. To illustrate this responsibility, let’s say that |
| on our view page, <code class="language-plaintext highlighter-rouge">HelloWorld.jsp</code>, we want to display a personal hello, such as “Hello Struts User Bruce.”</p> |
| |
| <p>In the <a href="using-tags">Using Struts 2 Tags</a> example application we added a Struts 2 form to <code class="language-plaintext highlighter-rouge">index.jsp</code>.</p> |
| |
| <p><strong>Struts 2 Form Tags</strong></p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><s:form</span> <span class="na">action=</span><span class="s">"hello"</span><span class="nt">></span> |
| <span class="nt"><s:textfield</span> <span class="na">name=</span><span class="s">"userName"</span> <span class="na">label=</span><span class="s">"Your name"</span> <span class="nt">/></span> |
| <span class="nt"><s:submit</span> <span class="na">value=</span><span class="s">"Submit"</span> <span class="nt">/></span> |
| <span class="nt"></s:form></span> |
| </code></pre></div></div> |
| |
| <p>Make a note of the value of the name attribute for the Struts 2 textfield tag, which is userName. When the user |
| clicks on the submit button for the above form, the action hello will be executed (<code class="language-plaintext highlighter-rouge">hello.action</code>). The form field |
| values will be posted to the Struts 2 Action class (<code class="language-plaintext highlighter-rouge">HelloWorldAction</code>). The Action class may automatically receive |
| those form field values provided it has a public set method that matches the form field name value.</p> |
| |
| <p>So for the HelloWorldAction class to automatically receive the userName value it must have a public method setUserName |
| (note the JavaBean convention discussed in tutorial <a href="hello-world-using-struts2">Hello World</a>).</p> |
| |
| <p>For the example application associated with this tutorial, add the following Java code to class <code class="language-plaintext highlighter-rouge">HelloWorldAction</code>.</p> |
| |
| <p><strong>Add userName to HelloWorldAction</strong></p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">private</span> <span class="nc">String</span> <span class="n">userName</span><span class="o">;</span> |
| |
| <span class="kd">public</span> <span class="nc">String</span> <span class="nf">getUserName</span><span class="o">()</span> <span class="o">{</span> |
| <span class="k">return</span> <span class="n">userName</span><span class="o">;</span> |
| <span class="o">}</span> |
| |
| <span class="nd">@StrutsParameter</span> |
| <span class="kd">public</span> <span class="kt">void</span> <span class="nf">setUserName</span><span class="o">(</span><span class="nc">String</span> <span class="n">userName</span><span class="o">)</span> <span class="o">{</span> |
| <span class="k">this</span><span class="o">.</span><span class="na">userName</span> <span class="o">=</span> <span class="n">userName</span><span class="o">;</span> |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| <p>To personalize the MessageStore message (recall that class MessageStore is storing the message to display) |
| add the following Java code to the HelloWorldAction’s execute method after the statement that instantiates |
| the MessageStore object.</p> |
| |
| <p><strong>Add userName value to message</strong></p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">if</span> <span class="o">(</span><span class="n">userName</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span> |
| <span class="n">messageStore</span><span class="o">.</span><span class="na">setMessage</span><span class="o">(</span> <span class="n">messageStore</span><span class="o">.</span><span class="na">getMessage</span><span class="o">()</span> <span class="o">+</span> <span class="s">" "</span> <span class="o">+</span> <span class="n">userName</span><span class="o">);</span> |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| <p>Now build and run (<code class="language-plaintext highlighter-rouge">mvn jetty:run</code>) the application. Enter your name in the form and click the submit button. |
| You should see the following page.</p> |
| |
| <p><img src="attachments/coding_actions_form_submit_result.png" alt="coding_actions_form_submit_result.png" /></p> |
| |
| <p>When the form is submitted, Struts will call any set methods of the HelloWorldAction class that match the form field |
| names and are annotated with <code class="language-plaintext highlighter-rouge">@StrutsParameter</code>. So in this example method <code class="language-plaintext highlighter-rouge">setUserName</code> was called and passed the value |
| the user entered in the <code class="language-plaintext highlighter-rouge">userName</code> form field.</p> |
| |
| <p>On the <code class="language-plaintext highlighter-rouge">index.jsp</code> we also have a Struts 2 action link (see tutorial <a href="using-tags">Using Struts 2 Tags</a>) that includes |
| a query string parameter: <code class="language-plaintext highlighter-rouge">userName=Bruce+Phillips</code>. If you click on that link you should see the following result:</p> |
| |
| <p><img src="attachments/coding_actions_link_with_param_result.png" alt="coding_actions_link_with_param_result.png" /></p> |
| |
| <p>Since the query string parameter is <code class="language-plaintext highlighter-rouge">userName</code>, Struts passed the value of that parameter to the <code class="language-plaintext highlighter-rouge">setUserName</code> method.</p> |
| |
| <p>On the view page, <code class="language-plaintext highlighter-rouge">HelloWorld.jsp</code>, you can also access the <code class="language-plaintext highlighter-rouge">userName</code> value by using the Struts 2 property tag |
| (see tutorial <a href="using-tags">Using Struts 2 Tags</a>). Try showing just the <code class="language-plaintext highlighter-rouge">userName</code> value on the view page.</p> |
| |
| <h2 id="summary">Summary</h2> |
| |
| <p>This tutorial introduced you to how to code the Action class so it can process user input on a form or values in |
| a query string parameter. If the form had numerous fields, it would be cumbersome to have a set method that matches |
| up with each form field. So our next tutorial will cover how to integrate a model class, form fields in the view |
| and form processing in the Action class.</p> |
| |
| <table> |
| <tbody> |
| <tr> |
| <td>Return to <a href="using-tags">Using Struts 2 Tags</a></td> |
| <td>or</td> |
| <td>onward to <a href="processing-forms">Processing Forms</a></td> |
| </tr> |
| </tbody> |
| </table> |
| |
| </section> |
| </article> |
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