The taakServlet controls execution of the taak
framework. The taakServlet is configured through
an XML configuration file. An example of a configuration file looks like
this:
<taak-config>
<class-prefix>com.nevik.client.view</class-prefix>
<preload>true</preload>
<reparse>true</reparse>
<mapping path="/login_action.htm"
script="login_action.taak"
/>
<mapping path="/sign_out.htm"
doc="logout.htm"
script="logout.taak"
/>
<mapping path="/hello.htm"
class="HelloView"
/>
</taak-config>
The class-prefix element specifies the
Java package of custom view classes specified elsewhere as the class attribute
of the mapping element.
The preload element specifies whether
the documents specified in the doc attribute
of the mapping elements will be loaded on startup. Valid values for this
element are true and
false. The default
for this element is true.
The reparse element specifies whether
the XHTML documents specified in the doc
attribute of the mapping elements will be reloaded and parsed automatically
when a new version is replace an older one. Valid values for this element
are true and false.
The default for this element is true.
The mapping element has the attributes:
| Attribute |
Description |
Required |
| path |
The virtual path of the URL. |
yes |
| class |
The Java class to handle this path. If unspecified the default handler
internal to the taakServlet is used. |
no |
| doc |
The relative path of the actual xhtml document to be served for
the virtual path. If unspecified, a document with the same name as
the virtual path is assumed. |
no |
| script |
The name of the taakScript to transform
the document before it is sent to the browser. If unspecified, the
script can also be included as the content of the mapping
element. |
no |
When the taakServlet receives an HTTP request,
it looks up the taak-config.xml file to find a match between the URL Request
and the path attribute by examining each
mapping element. The document specified
in the doc attribute is optional. If
the document exists, the document is retrieved and parsed into a JDOM
object. Next, the taakServlet examines the remaining
attribute in the mapping element to determine
the executable element (also called a handler) for the request. The handler
can be either a Taak script, or a Java class, or neither. A taakScript
can be specified in an external file by using the script
attribute. A Java class is specified using the class attribute. A use
of Taak and Java classes as handlers is mutually exclusive. Only one or
the other should be specified. If neither a Java handler nor a Taak script
is specified, the document is sent to the user after any optional URL
rewriting in done.
If a handler is specified, an execution context is set up and the handler
is executed. The context provides to the handler input from the user through
the ServletRequest, and the optional XHTML document as a JDOM object.
The handler is responsible for retrieving additional data to complete
its processing.
The handler may complete processing in one of the following ways:
- Throwing an exception.
- Redirecting to another page.
- Forwarding to another page.
- Writing XHTML to the servlet output stream.
- Modifying a JDOM object. In this case, the servlet will complete processing
by doing URL rewriting and outputting the JDOM object as XHTML to the
user.
|
