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| <h1 class="no_toc" id="result-configuration">Result Configuration</h1> |
| |
| <ul id="markdown-toc"> |
| <li><a href="#result-elements" id="markdown-toc-result-elements">Result Elements</a></li> |
| <li><a href="#multiple-names" id="markdown-toc-multiple-names">Multiple names</a></li> |
| <li><a href="#global-results" id="markdown-toc-global-results">Global Results</a></li> |
| <li><a href="#dynamic-results" id="markdown-toc-dynamic-results">Dynamic Results</a></li> |
| <li><a href="#returning-result-objects" id="markdown-toc-returning-result-objects">Returning Result Objects</a></li> |
| </ul> |
| |
| <p>When an <code class="highlighter-rouge">action</code> class method completes, it returns a String. The value of the String is used to select a result element. |
| An action mapping will often have a set of results representing different possible outcomes. A standard set of result |
| tokens are defined by the <code class="highlighter-rouge">ActionSupport</code> base class.</p> |
| |
| <p><strong>Predefined result names</strong></p> |
| |
| <div class="highlighter-rouge"><div class="highlight"><pre class="highlight"><code>String SUCCESS = "success"; |
| String NONE = "none"; |
| String ERROR = "error"; |
| String INPUT = "input"; |
| String LOGIN = "login"; |
| </code></pre></div></div> |
| |
| <p>Of course, applications can define other result tokens to match specific cases.</p> |
| |
| <blockquote> |
| <p>Returning <code class="highlighter-rouge">ActionSupport.NONE</code> (or <code class="highlighter-rouge">null</code>) from an action class method causes the results processing |
| to be skipped. This is useful if the action fully handles the result processing such as writing directly |
| to the HttpServletResponse OutputStream.</p> |
| </blockquote> |
| |
| <h2 id="result-elements">Result Elements</h2> |
| |
| <p>The result element has two jobs. First, it provides a logical name. An <code class="highlighter-rouge">Action</code> can pass back a token like <code class="highlighter-rouge">success</code> |
| or <code class="highlighter-rouge">error</code> without knowing any other implementation details. Second, the result element provides a result type. Most |
| results simply forward to a server page or template, but other <a href="result-types.html">Result Types</a> can be used to do more |
| interesting things.</p> |
| |
| <p><strong>Intelligent Defaults</strong></p> |
| |
| <p>Each package may set a default result type to be used if none is specified in a result element. If one package extends |
| another, the “child” package can set its own default result, or inherit one from the parent.</p> |
| |
| <p><strong>Setting a default Result Type</strong></p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><result-types></span> |
| <span class="nt"><result-type</span> <span class="na">name=</span><span class="s">"dispatcher"</span> <span class="na">default=</span><span class="s">"true"</span> <span class="na">class=</span><span class="s">"org.apache.struts2.dispatcher.ServletDispatcherResult"</span> <span class="nt">/></span> |
| <span class="nt"></result-types></span> |
| </code></pre></div></div> |
| |
| <p>If a <code class="highlighter-rouge">type</code> attribute is not specified, the framework will use the default <code class="highlighter-rouge">dispatcher</code> type, which forwards to another |
| web resource. If the resource is a JavaServer Page, then the container will render it, using its JSP engine.</p> |
| |
| <p>Likewise if the <code class="highlighter-rouge">name</code> attribute is not specified, the framework will give it the name <code class="highlighter-rouge">success</code>.</p> |
| |
| <p>Using these intelligent defaults, the most often used result types also become the simplest.</p> |
| |
| <p><strong>Result element without defaults</strong></p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><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> |
| <span class="nt"><param</span> <span class="na">name=</span><span class="s">"location"</span><span class="nt">></span>/ThankYou.jsp<span class="nt"></param></span> |
| <span class="nt"></result></span> |
| </code></pre></div></div> |
| |
| <p><strong>A Result element using some defaults</strong></p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><result></span> |
| <span class="nt"><param</span> <span class="na">name=</span><span class="s">"location"</span><span class="nt">></span>/ThankYou.jsp<span class="nt"></param></span> |
| <span class="nt"></result></span> |
| </code></pre></div></div> |
| |
| <p>The <code class="highlighter-rouge">param</code> tag sets a property on the Result object. The most commonly-set property is <code class="highlighter-rouge">location</code>, which usually |
| specifies the path to a web resources. The <code class="highlighter-rouge">param</code> attribute is another intelligent default.</p> |
| |
| <p><strong>Result element using more defaults</strong></p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><result></span>/ThankYou.jsp<span class="nt"></result></span> |
| </code></pre></div></div> |
| |
| <p>Mixing results with intelligent defaults with other results makes it easier to see the “critical path”.</p> |
| |
| <p><strong>Multiple Results</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="nt">></span> |
| <span class="nt"><result></span>/hello/Result.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"error"</span><span class="nt">></span>/hello/Error.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"input"</span><span class="nt">></span>/hello/Input.jsp<span class="nt"></result></span> |
| <span class="nt"></action></span> |
| </code></pre></div></div> |
| |
| <p>A special “other” result can be configured by adding a result with <code class="highlighter-rouge">name="*"</code>. This result will only be selected if no |
| result is found with a matching name.</p> |
| |
| <p><strong>‘*’ Other Result</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="nt">></span> |
| <span class="nt"><result></span>/hello/Result.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"error"</span><span class="nt">></span>/hello/Error.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"input"</span><span class="nt">></span>/hello/Input.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"*"</span><span class="nt">></span>/hello/Other.jsp<span class="nt"></result></span> |
| <span class="nt"></action></span> |
| </code></pre></div></div> |
| |
| <blockquote> |
| <p>The <code class="highlighter-rouge">name="*"</code> is <strong>not</strong> a wildcard pattern, it is a special name that is only selected if an exact match is not found.</p> |
| </blockquote> |
| |
| <blockquote> |
| <p>In most cases if an action returns an unrecognized result name this would be a programming error and should be fixed.</p> |
| </blockquote> |
| |
| <h2 id="multiple-names">Multiple names</h2> |
| |
| <p>It is possible to define multiple names for the same result:</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">"save"</span><span class="nt">></span> |
| <span class="nt"><result></span>success.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"error, input"</span><span class="nt">></span>input-form.jsp<span class="nt"></result></span> |
| <span class="nt"></action></span> |
| </code></pre></div></div> |
| |
| <p>Such functionality was added in Struts 2.5</p> |
| |
| <h2 id="global-results">Global Results</h2> |
| |
| <p>Most often, results are nested with the action element. But some results apply to multiple actions. In a secure |
| application, a client might try to access a page without being authorized, and many actions may need access |
| to a <code class="highlighter-rouge">logon</code> result.</p> |
| |
| <p>If actions need to share results, a set of global results can be defined for each package. The framework will first |
| look for a local result nested in the action. If a local match is not found, then the global results are checked.</p> |
| |
| <p><strong>Defining global results</strong></p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><global-results></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"error"</span><span class="nt">></span>/Error.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"invalid.token"</span><span class="nt">></span>/Error.jsp<span class="nt"></result></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"login"</span> <span class="na">type=</span><span class="s">"redirectAction"</span><span class="nt">></span>Logon!input<span class="nt"></result></span> |
| <span class="nt"></global-results></span> |
| </code></pre></div></div> |
| |
| <blockquote> |
| <p>For more about results, see <a href="result-types.html">Result Types</a>.</p> |
| </blockquote> |
| |
| <h2 id="dynamic-results">Dynamic Results</h2> |
| |
| <p>A result may not be known until execution time. Consider the implementation of a state-machine-based execution flow; |
| the next state might depend on any combination of form input elements, session attributes, user roles, moon phase, etc. |
| In other words, determining the next action, input page, etc. may not be known at configuration time.</p> |
| |
| <p>Result values may be retrieved from its corresponding Action implementation by using EL expressions that access |
| the Action’s properties, just like the Struts 2 tag libraries. So given the following Action fragment:</p> |
| |
| <p><strong>FragmentAction implementation</strong></p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">private</span> <span class="n">String</span> <span class="n">nextAction</span><span class="o">;</span> |
| |
| <span class="kd">public</span> <span class="n">String</span> <span class="nf">getNextAction</span><span class="o">()</span> <span class="o">{</span> |
| <span class="k">return</span> <span class="n">nextAction</span><span class="o">;</span> |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| <p>you might define a result like this:</p> |
| |
| <p><strong>FragmentAction configuration</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">"fragment"</span> <span class="na">class=</span><span class="s">"FragmentAction"</span><span class="nt">></span> |
| <span class="nt"><result</span> <span class="na">name=</span><span class="s">"next"</span> <span class="na">type=</span><span class="s">"redirectAction"</span><span class="nt">></span>${nextAction}<span class="nt"></result></span> |
| <span class="nt"></action></span> |
| </code></pre></div></div> |
| |
| <p>If a <code class="highlighter-rouge">FragmentAction</code> method returns <code class="highlighter-rouge">next</code> the actual <em>value</em> of that result will be whatever is in <code class="highlighter-rouge">FragmentAction</code>’s |
| <code class="highlighter-rouge">nextAction</code> property. So <code class="highlighter-rouge">nextAction</code> may be computed based on whatever state information necessary then passed |
| at runtime to <code class="highlighter-rouge">next</code>’s <code class="highlighter-rouge">redirectAction</code>.</p> |
| |
| <p>See <a href="../faq/parameters-in-configuration-results.html">Parameters in configuration results</a> for an expanded discussion. </p> |
| |
| <h2 id="returning-result-objects">Returning Result Objects</h2> |
| |
| <p>Instead of configuring results and returning the name, it is possible to return a result object:</p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">public</span> <span class="n">Result</span> <span class="nf">runAction</span><span class="o">()</span> <span class="o">{</span> |
| <span class="n">ServletDispatcherResult</span> <span class="n">result</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ServletDispatcherResult</span><span class="o">();</span> |
| <span class="n">result</span><span class="o">.</span><span class="na">setLocation</span><span class="o">(</span><span class="s">"input-form.jsp"</span><span class="o">);</span> |
| <span class="k">return</span> <span class="n">result</span><span class="o">;</span> |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| </section> |
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