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 <html><head>
       <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>2.7.&nbsp;Page Actions</title><link rel="stylesheet" href="css/stylesheet.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.0"><link rel="home" href="index.html" title="Apache Click"><link rel="up" href="ch02.html" title="Chapter&nbsp;2.&nbsp;Pages"><link rel="prev" href="ch02s06.html" title="2.6.&nbsp;Page Templating"><link rel="next" href="ch02s08.html" title="2.8.&nbsp;Direct Rendering"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2.7.&nbsp;Page Actions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch02s06.html">Prev</a>&nbsp;</td><th width="60%" align="center">Chapter&nbsp;2.&nbsp;Pages</th><td width="20%" align="right">&nbsp;<a accesskey="n" href="ch02s08.html">Next</a></td></tr></table><hr></div><div class="sect1" title="2.7.&nbsp;Page Actions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="page-actions"></a>2.7.&nbsp;Page Actions</h2></div></div></div><p>Page Action is a feature to directly invoke a <code class="literal">Page method</code>
     from the browser. The Page Action method returns an
     <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="../../click-api/org/apache/click/ActionResult.html" target="_blank">ActionResult</a>
     object that is rendered directly to the browser. In other words the Page template will
     not be rendered.
     </p><p>To invoke a Page Action, specify the parameter <code class="varname">"pageAction"</code>
     and the name of the page method, for example: <span class="symbol">"onRenderImage"</span>.
     </p><p>Let's take a quick look at how a Page Action can be leveraged to retrieve
     an image. In this example we'll create an HTML <code class="literal">&lt;img&gt;</code>
     element which <code class="literal">src</code> attribute specifies the Page Action
     that will return the image data.
     </p><p>First we create our template:
     </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag">&lt;img</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="atn">src</span>=<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="pln">"$context/mycorp/image.htm?</span><code class="varname">pageAction</code>=<span class="symbol">onRenderImage</span>"/&gt;
 </pre><p>Next we create our ImagePage with a Page Action method called
     <span class="symbol">onRenderImage</span> that returns an <span class="token">ActionResult</span>
     instance:
     </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">class</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span class="token">ActionResult</span> <span class="symbol">onRenderImage()</span> {
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = getImageAsBytes();
         String contentType = ClickUtils.getMimeType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> <span class="token">ActionResult</span>(imageData, contentType);
     }
 } </pre><p>A Page Action is a normal Page method with the following signature:
     a <span class="symbol">public no-arg</span> method returning an <span class="token">ActionResult</span>
     instance:
     </p><pre class="programlisting">
 <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// The Page Action method is public, doesn't accept any arguments and returns an ActionResult</span>
 <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span class="token">ActionResult</span> <span class="symbol">onRenderImage()</span> {
     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = getImageAsBytes();
     String contentType = ClickUtils.getMimeType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> <span class="token">ActionResult</span>(imageData, contentType);
 } </pre><p>The <span class="token">ActionResult</span> contains the data that is rendered to
     the client browser. In the example above, the result will the Image byte array
     with a Content-Type of: <code class="literal">"images/png"</code>.
     </p><div class="sect2" title="2.7.1.&nbsp;Page Action Execution"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-execution"></a>2.7.1.&nbsp;Page Action Execution</h3></div></div></div><p>Page Actions are page methods that handle the processing of a user
         request and render a result to the browser. The execution sequence for a
         Page Action being processed and rendered is illustrated in the figure below.
         </p><div class="figure"><a name="page-action-sequence-diagram"></a><div class="figure-contents"><span class="inlinemediaobject"><img src="images/pages/page-action-sequence-diagram.png" alt="Page Action Request Sequence Diagram"></span></div><p xmlns:fo="http://www.w3.org/1999/XSL/Format" class="title"><i>Figure&nbsp;2.5.&nbsp;Page Action Request Sequence Diagram
           </i></p></div><br class="figure-break"><p>Stepping through this Page Action request sequence, a new Page instance
         is created and the attributes for the Page are set (format, headers). Next,
         request parameter values are bound to matching Page fields.
         </p><p>Then the <code class="methodname">onSecurityCheck()</code> handler is executed.
         This method can be used to ensure the user is authorized to access the Page Action,
         and if necessary abort any further processing. If
         <code class="methodname">onSecurityCheck()</code> return false, no response is
         sent back to the client. Note, if you want to send a specific response to
         the client you have to do that from the
         <code class="methodname">onSecurityCheck()</code> event, since other Page events
         are not executed. Please see
         <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="http://click.avoka.com/click-examples/ajax/ajax-secure.htm" target="_blank">this</a>
         example for some strategies on implementing
         <code class="methodname">onSecurityCheck</code>  to handle ajax requests.
             </p><p>Next the target <code class="methodname">page method</code> is invoked
         which returns an <code class="classname">ActionResult</code> that is rendered to
         the client.</p><p>If the page method returns <code class="literal">null</code> no response is
         rendered to the browser.
         </p></div><div class="sect2" title="2.7.2.&nbsp;ActionResult"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-result"></a>2.7.2.&nbsp;ActionResult</h3></div></div></div><p>An ActionResult represents the content returned by a Page Action
         which is then rendered to the client browser. ActionResults normally
         contains HTML or image data that is rendered to the browser. When a Page
         Action is invoked the Page template rendering is bypassed and only the
         ActionResult content is rendered to the browser. This allows a Page Action
         to return a "partial" response, as opposed to a "full" response, because
         the Page template (which can be viewed as a "full" response) is bypassed
         when invoking a Page Action.
         </p></div><div class="sect2" title="2.7.3.&nbsp;Page Action Example"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-example"></a>2.7.3.&nbsp;Page Action Example</h3></div></div></div><p>Let's step through a Page Action example. First we create an ImagePage
         class with the method "getImageData" which is the Page Action we want to invoke:
         </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ActionResult getImageData() {
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = loadImageData();
         String contentType = ClickUtils.getContentType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> ActionResult(imageData, contentType);
     }
 } </pre><p>Next we have the page template image.htm:
         </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag">&lt;html&gt;</span>
   <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag">&lt;body&gt;</span>

     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag">&lt;img</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="atn">src</span>=<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="pln">"/mycorp/image.htm?</span><code class="varname">pageAction</code>=<span class="symbol">getImageData</span>"/&gt;

   <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag">&lt;/body&gt;</span>
 <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag">&lt;/html&gt;</span> </pre><p>The browser renders the <code class="literal">&lt;img&gt;</code> element and
       requests the image src url. Click invokes the page method <span class="symbol">getImageData</span>
       and renders the result to the browser.
       </p><p>Looking at the output log we see the following trace:
       </p><div class="literallayout"><p>[Click]&nbsp;[info&nbsp;]&nbsp;handleRequest:&nbsp;&nbsp;/image.htm&nbsp;-&nbsp;84&nbsp;ms<br>
 [Click]&nbsp;[debug]&nbsp;GET&nbsp;http://localhost:8080/mycorp/image.htm<br>
 [Click]&nbsp;[trace]&nbsp;&nbsp;&nbsp;&nbsp;is&nbsp;Ajax&nbsp;request:&nbsp;false<br>
 [Click]&nbsp;[trace]&nbsp;&nbsp;&nbsp;&nbsp;request&nbsp;param:&nbsp;pageAction=getImageData<br>
 [Click]&nbsp;[trace]&nbsp;&nbsp;&nbsp;&nbsp;invoked:&nbsp;ImagePage.&lt;&lt;init&gt;&gt;<br>
 [Click]&nbsp;[trace]&nbsp;&nbsp;&nbsp;&nbsp;invoked:&nbsp;ImagePage.onSecurityCheck()&nbsp;:&nbsp;true<br>
 [Click]&nbsp;[trace]&nbsp;&nbsp;&nbsp;&nbsp;invoked:&nbsp;ImagePage.getImageData()&nbsp;:&nbsp;ActionResult<br>
 [Click]&nbsp;[info&nbsp;]&nbsp;&nbsp;&nbsp;&nbsp;renderActionResult&nbsp;(image/png)&nbsp;-&nbsp;0&nbsp;ms<br>
 [Click]&nbsp;[trace]&nbsp;&nbsp;&nbsp;&nbsp;invoked:&nbsp;ImagePage.onDestroy()<br>
 [Click]&nbsp;[info&nbsp;]&nbsp;handleRequest:&nbsp;&nbsp;/image.htm&nbsp;-&nbsp;98&nbsp;ms</p></div></div><div class="sect2" title="2.7.4.&nbsp;Accessing Request Parameters"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-accessing-request-parameters"></a>2.7.4.&nbsp;Accessing Request Parameters</h3></div></div></div><p>Request parameters can be accessed through the <code class="classname">Context</code>
         as shown below:
         </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ActionResult getImageData() {
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// Retrieve a request parameter through the Context</span>
         Context context = getContext();
         String imageName = context.getRequestParameter(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"imageName"</span>);

         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = loadImageData(imageName);
         String contentType = ClickUtils.getContentType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> ActionResult(imageData, contentType);
     }
 } </pre></div><div class="sect2" title="2.7.5.&nbsp;Set response headers and status code"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-set-response-headers"></a>2.7.5.&nbsp;Set response headers and status code</h3></div></div></div><p>When handling a Page Action you might need to set the HTTP response
       headers or status code. You do this through the Servlet API's,
       <code class="classname">HttpServetlResponse</code> which can be accessed
       through the <code class="classname">Context</code>.
       </p><p>For example:
       </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">package</span> examples.page;

 <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">import</span> java.util.Date;
 <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">import</span> org.apache.click.Page;

 <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

     <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ActionResult getImageData() {
         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// Headers and Status code are set on the HttpServletResponse</span>
         HttpServletResponse response = getContext().getResponse();

         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// The headers can be set as follows:</span>
         response.setHeader(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"Content-Disposition"</span>, <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"attachment; filename=\"report.xls\""</span>);

         ...

         <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// The response status can be set as follows:</span>
         response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);

         ...
     }
 } </pre></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch02s06.html">Prev</a>&nbsp;</td><td width="20%" align="center"><a accesskey="u" href="ch02.html">Up</a></td><td width="40%" align="right">&nbsp;<a accesskey="n" href="ch02s08.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2.6.&nbsp;Page Templating&nbsp;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;2.8.&nbsp;Direct Rendering</td></tr></table></div></body></html>
	<html><head>
	<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
	<title>2.7. Page Actions</title><link rel="stylesheet" href="css/stylesheet.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.0"><link rel="home" href="index.html" title="Apache Click"><link rel="up" href="ch02.html" title="Chapter 2. Pages"><link rel="prev" href="ch02s06.html" title="2.6. Page Templating"><link rel="next" href="ch02s08.html" title="2.8. Direct Rendering"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2.7. Page Actions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch02s06.html">Prev</a> </td><th width="60%" align="center">Chapter 2. Pages</th><td width="20%" align="right"> <a accesskey="n" href="ch02s08.html">Next</a></td></tr></table><hr></div><div class="sect1" title="2.7. Page Actions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="page-actions"></a>2.7. Page Actions</h2></div></div></div><p>Page Action is a feature to directly invoke a <code class="literal">Page method</code>
	from the browser. The Page Action method returns an
	<a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="../../click-api/org/apache/click/ActionResult.html" target="_blank">ActionResult</a>
	object that is rendered directly to the browser. In other words the Page template will
	not be rendered.
	</p><p>To invoke a Page Action, specify the parameter <code class="varname">"pageAction"</code>
	and the name of the page method, for example: <span class="symbol">"onRenderImage"</span>.
	</p><p>Let's take a quick look at how a Page Action can be leveraged to retrieve
	an image. In this example we'll create an HTML <code class="literal"><img></code>
	element which <code class="literal">src</code> attribute specifies the Page Action
	that will return the image data.
	</p><p>First we create our template:
	</p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag"><img</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="atn">src</span>=<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="pln">"$context/mycorp/image.htm?</span><code class="varname">pageAction</code>=<span class="symbol">onRenderImage</span>"/>
	</pre><p>Next we create our ImagePage with a Page Action method called
	<span class="symbol">onRenderImage</span> that returns an <span class="token">ActionResult</span>
	instance:
	</p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">class</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span class="token">ActionResult</span> <span class="symbol">onRenderImage()</span> {
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = getImageAsBytes();
	String contentType = ClickUtils.getMimeType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> <span class="token">ActionResult</span>(imageData, contentType);
	}
	} </pre><p>A Page Action is a normal Page method with the following signature:
	a <span class="symbol">public no-arg</span> method returning an <span class="token">ActionResult</span>
	instance:
	</p><pre class="programlisting">
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// The Page Action method is public, doesn't accept any arguments and returns an ActionResult</span>
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span class="token">ActionResult</span> <span class="symbol">onRenderImage()</span> {
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = getImageAsBytes();
	String contentType = ClickUtils.getMimeType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> <span class="token">ActionResult</span>(imageData, contentType);
	} </pre><p>The <span class="token">ActionResult</span> contains the data that is rendered to
	the client browser. In the example above, the result will the Image byte array
	with a Content-Type of: <code class="literal">"images/png"</code>.
	</p><div class="sect2" title="2.7.1. Page Action Execution"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-execution"></a>2.7.1. Page Action Execution</h3></div></div></div><p>Page Actions are page methods that handle the processing of a user
	request and render a result to the browser. The execution sequence for a
	Page Action being processed and rendered is illustrated in the figure below.
	</p><div class="figure"><a name="page-action-sequence-diagram"></a><div class="figure-contents"><span class="inlinemediaobject"><img src="images/pages/page-action-sequence-diagram.png" alt="Page Action Request Sequence Diagram"></span></div><p xmlns:fo="http://www.w3.org/1999/XSL/Format" class="title"><i>Figure 2.5. Page Action Request Sequence Diagram
	</i></p></div><br class="figure-break"><p>Stepping through this Page Action request sequence, a new Page instance
	is created and the attributes for the Page are set (format, headers). Next,
	request parameter values are bound to matching Page fields.
	</p><p>Then the <code class="methodname">onSecurityCheck()</code> handler is executed.
	This method can be used to ensure the user is authorized to access the Page Action,
	and if necessary abort any further processing. If
	<code class="methodname">onSecurityCheck()</code> return false, no response is
	sent back to the client. Note, if you want to send a specific response to
	the client you have to do that from the
	<code class="methodname">onSecurityCheck()</code> event, since other Page events
	are not executed. Please see
	<a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="http://click.avoka.com/click-examples/ajax/ajax-secure.htm" target="_blank">this</a>
	example for some strategies on implementing
	<code class="methodname">onSecurityCheck</code> to handle ajax requests.
	</p><p>Next the target <code class="methodname">page method</code> is invoked
	which returns an <code class="classname">ActionResult</code> that is rendered to
	the client.</p><p>If the page method returns <code class="literal">null</code> no response is
	rendered to the browser.
	</p></div><div class="sect2" title="2.7.2. ActionResult"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-result"></a>2.7.2. ActionResult</h3></div></div></div><p>An ActionResult represents the content returned by a Page Action
	which is then rendered to the client browser. ActionResults normally
	contains HTML or image data that is rendered to the browser. When a Page
	Action is invoked the Page template rendering is bypassed and only the
	ActionResult content is rendered to the browser. This allows a Page Action
	to return a "partial" response, as opposed to a "full" response, because
	the Page template (which can be viewed as a "full" response) is bypassed
	when invoking a Page Action.
	</p></div><div class="sect2" title="2.7.3. Page Action Example"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-example"></a>2.7.3. Page Action Example</h3></div></div></div><p>Let's step through a Page Action example. First we create an ImagePage
	class with the method "getImageData" which is the Page Action we want to invoke:
	</p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ActionResult getImageData() {
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = loadImageData();
	String contentType = ClickUtils.getContentType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> ActionResult(imageData, contentType);
	}
	} </pre><p>Next we have the page template image.htm:
	</p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag"><html></span>
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag"><body></span>

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag"><img</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="atn">src</span>=<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="pln">"/mycorp/image.htm?</span><code class="varname">pageAction</code>=<span class="symbol">getImageData</span>"/>

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag"></body></span>
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="tag"></html></span> </pre><p>The browser renders the <code class="literal"><img></code> element and
	requests the image src url. Click invokes the page method <span class="symbol">getImageData</span>
	and renders the result to the browser.
	</p><p>Looking at the output log we see the following trace:
	</p><div class="literallayout"><p>[Click] [info ] handleRequest:  /image.htm - 84 ms<br>
	[Click] [debug] GET http://localhost:8080/mycorp/image.htm<br>
	[Click] [trace]    is Ajax request: false<br>
	[Click] [trace]    request param: pageAction=getImageData<br>
	[Click] [trace]    invoked: ImagePage.<<init>><br>
	[Click] [trace]    invoked: ImagePage.onSecurityCheck() : true<br>
	[Click] [trace]    invoked: ImagePage.getImageData() : ActionResult<br>
	[Click] [info ]    renderActionResult (image/png) - 0 ms<br>
	[Click] [trace]    invoked: ImagePage.onDestroy()<br>
	[Click] [info ] handleRequest:  /image.htm - 98 ms</p></div></div><div class="sect2" title="2.7.4. Accessing Request Parameters"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-accessing-request-parameters"></a>2.7.4. Accessing Request Parameters</h3></div></div></div><p>Request parameters can be accessed through the <code class="classname">Context</code>
	as shown below:
	</p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ActionResult getImageData() {
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// Retrieve a request parameter through the Context</span>
	Context context = getContext();
	String imageName = context.getRequestParameter(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"imageName"</span>);

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">byte</span>[] imageData = loadImageData(imageName);
	String contentType = ClickUtils.getContentType(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"png"</span>);
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">new</span> ActionResult(imageData, contentType);
	}
	} </pre></div><div class="sect2" title="2.7.5. Set response headers and status code"><div class="titlepage"><div><div><h3 class="title"><a name="page-action-set-response-headers"></a>2.7.5. Set response headers and status code</h3></div></div></div><p>When handling a Page Action you might need to set the HTTP response
	headers or status code. You do this through the Servlet API's,
	<code class="classname">HttpServetlResponse</code> which can be accessed
	through the <code class="classname">Context</code>.
	</p><p>For example:
	</p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">package</span> examples.page;

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">import</span> java.util.Date;
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">import</span> org.apache.click.Page;

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ImagePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page {

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> ActionResult getImageData() {
	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// Headers and Status code are set on the HttpServletResponse</span>
	HttpServletResponse response = getContext().getResponse();

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// The headers can be set as follows:</span>
	response.setHeader(<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"Content-Disposition"</span>, <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="str">"attachment; filename=\"report.xls\""</span>);

	...

	<span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="com">// The response status can be set as follows:</span>
	response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);

	...
	}
	} </pre></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch02s06.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch02s08.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2.6. Page Templating </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 2.8. Direct Rendering</td></tr></table></div></body></html>