jford 2004/04/09 08:52:46
Added: tutorial/xdocs/6 mediatypes.xml
Log:
Chapter 6 conversion to xdoc
Revision Changes Path
1.1 jakarta-jetspeed/tutorial/xdocs/6/mediatypes.xml
Index: mediatypes.xml
===================================================================
<?xml version="1.0"?>
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you may not use this file except in compliance with the License.
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<document>
<properties>
<author email="[EMAIL PROTECTED]">David Sean Taylor</author>
<title>Media Types</title>
</properties>
<body>
<section name="Media Types">
<p>
The content generated is dependent on the media type supported by the browser.
Browsers (devices) supply request parameters describing the capabilities of device.
For instance, a web browser would provide in its request parameters a description of
which <a href="http://www.nacs.uci.edu/indiv/ehood/MIME/MIME.html";>MIME types</a> and
languages it supports.
Jetspeed packages this all up in a request object call <a
href="http://portals.apache.org/jetspeed-1/apidocs/org/apache/jetspeed/services/rundata/JetspeedRunData.html";>JetspeedRunData</a>.
You can check the request for the media type by getting the <a
href="http://portals.apache.org/jetspeed-1/apidocs/org/apache/jetspeed/capability/CapabilityMap.html";>CapabilityMap</a>
associated with the request (<b>rundata.getCapabilityMap</b>) and the checking the
media type against the supported media types for your portlet.
</p>
<p>
<img src="../images/image006-2.jpg"/>
</p>
<p>
Let's take a look at how the HelloPortletInterface portlet checks the media type
during content fragment generation:
</p>
<p>
<source>
<![CDATA[
public ConcreteElement getContent(RunData rundata)
{
JetspeedRunData jrun = (JetspeedRunData) rundata;
CapabilityMap map = jrun.getCapability();
StringBuffer text = new StringBuffer();
String mimeType = map.getPreferredType().toString();
if (this.supportsType(map.getPreferredType()))
{
text.append("Supports preferred MimeType: " + mimeType);
}
else
{
text.append("Doesn't support preferred MimeType: "
+ mimeType);
}
...
]]>
</source>
</p>
<p>
Every portlet has the <b>supportsType</b> method for checking a browser device's
MIME type.
The Media Types are looked up from the portlet definition in the registry.
Looking at the registry entry for <b>HelloPortletInterface</b>, we see the supported
media types are directly in the registry definition:
</p>
<p>
<source>
<![CDATA[
<portlet-entry name="HelloPortletInterface"
hidden="false" type="instance" application="false">
<meta-info>
<title>Hello Portlet Interface</title>
<description>JPortal Tutorial - Hello Portlet Interface
</description>
</meta-info>
<classname>com.bluesunrise.jportal.portal.portlets.HelloPortletInterface</classname>
<parameter name="version" value="1.4b4" hidden="false"/>
<media-type ref="html"/>
<media-type ref="wml"/>
<category>tutorial</category>
<category>portlet</category>
</portlet-entry>
]]>
</source>
</p>
<p>
There can be multiple <media-type> entries per portlet.
</p>
<p>
Media types are defined in the <a
href="http://portals.apache.org/jetspeed-1/client-media.html";>Media Type Registry</a>.
Four media types are currently supported in the registry:
</p>
<p>
<ul>
<li>HTML</li>
<li>WML</li>
<li>XML</li>
<li>VXML</li>
</ul>
</p>
<p>
<source>
<![CDATA[
<media-type-entry name="html">
<mime-type>text/html</mime-type>
<character-set>UTF-8</character-set>
<meta-info>
<title>HTML</title>
<description>Rich HTML for HTML 4.0 compliants browsers
</description>
</meta-info>
</media-type-entry>
]]>
</source>
</p>
<p>
Also note that the <b>getContent</b> method returns a class called
<b>ConcreteElement</b>.
</p>
<p>
<source>
<![CDATA[
import org.apache.ecs.ConcreteElement;
import org.apache.ecs.StringElement;
]]>
</source>
</p>
<p>
Unfortunately, Jetspeed is coupled to the Element Construction Set, a Java-based
HTML mark-up generator.
As you will see in the tutorials 7 and onwards, you shouldn't have to work much with
ECS or the low level methods of the Portlet interface.
Jetspeed provides a better way of getting content using templating engines such as
Velocity or JSP, along with RSS and XSLT ready-written portlets that you can extend.
</p>
<p>
For more information on <b>RunData</b> class and ECS elements, see <a
href="../AppendixB/index.html">Appendix B - Turbine and ECS</a>.
</p>
</section>
</body>
</document>
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