GenericPortlet:
GenericPortlet
is abstract class and it extends Object class and implements
Portlet,PortletConfig interfaces.
The GenericPortlet
class provides a default implementation for the Portlet interface.It provides
an abstract class to be subclassed to create portlets. A subclass of
GenericPortlet should override at least one method, usually one of the
following:
processAction, to handle action requests
doView, to handle render requests when in
VIEW mode
doEdit, to handle render requests when in
EDIT mode
doHelp, to handle render request when in
HELP mode
init and destroy, to manage resources that
are held for the life of the servlet
Normally
there is no need to override the render or the doDispatch methods. Render
handles render requests setting the title of the portlet in the response and
invoking doDispatch. doDispatch dispatches the request to one of the doView,
doEdit or doHelp method depending on the portlet mode indicated in the request.
Portlets
typically run on multithreaded servers, so please note that a portlet must
handle concurrent requests and be careful to synchronize access to shared resources.
Shared resources include in-memory data such as instance or class variables and
external objects such as files, database connections, and network connections.
Methods in
GenericPortlet:
destroy
()
getInitParameter
(java.lang.String name)
getResourceBundle
(java.util.Locale locale)
init
()
init:
Called by the
portlet container to indicate to a portlet that the portlet is being placed
into service.
The default implementation just
stores the PortletConfig object.
The portlet container calls the init
method exactly once after instantiating the portlet. The init
method must complete successfully before the portlet can receive any requests.
The portlet container cannot place
the portlet into service if the init method does one of the following:
1.
it throws a PortletException
2.
it does not return within a time period
defined by the Web server
A convenience method which can be overridden so that there's
no need to call super.init(config).
Instead of overriding init(PortletConfig), simply override this method and it will be called by GenericPortlet.init(PortletConfig
config). The PortletConfig
object can still be retrieved via getPortletConfig().
processAction:
Called by the portlet container to
allow the portlet to process an action request. This method is called if the
client request was originated by a URL created (by the portlet) with the RenderResponse.createActionURL() method.
The default implementation throws an exception.
Specified by:
render:
The default implementation of this
method sets the title using the getTitle method
and invokes the doDispatch method.
Specified by:
getTitle:
Used by the render method to get the title. The default
implementation gets the title from the ResourceBundle of the PortletConfig of the
portlet. The title is retrieved using the 'javax.portlet.title' resource name.Portlets
can overwrite this method to provide dynamic titles (e.g. based on locale,
client, and session information). Examples are:
- language-dependant
titles for multi-lingual portals
- shorter
titles for WAP phones
- the
number of messages in a mailbox portlet
Returns:
the portlet title for this window
doDispatch:
The default implementation of this
method routes the render request to a set of helper methods depending on the
current portlet mode the portlet is currently in. These methods are:
·
doView for handling view requests
·
doEdit for handling edit requests
·
doHelp for handling help requests
If the window state of this portlet is minimized, this method does not invoke any of the portlet mode
rendering methods. For handling custom portlet modes the portlet should
override this method.
doView:
protected void doView(RenderRequest request,
RenderResponse response)throws
PortletException,java.io.IOException
Helper method to serve up the
mandatory view mode. The default implementation throws an exception.
doEdit:
Helper method to serve up the edit
mode. The default implementation throws an exception.
doHelp:
protected void doHelp(RenderRequest request,RenderResponse response)throws
PortletException,java.io.IOException
Helper method to serve up the help
mode. The default implementation throws an exception.
getPortletConfig:
Returns the PortletConfig object of this portlet.
Returns:
the PortletConfig object of this portlet
destroy:
public void destroy()
Called by the portlet container to
indicate to a portlet that the portlet is being taken out of service. The
default implementation does nothing.
Specified by:
getPortletName:
public java.lang.String getPortletName()
Returns the name of this portlet.
Specified by:
getPortletContext:
Returns the PortletContext of the portlet application the portlet is in.
Specified by:
getResourceBundle:
public java.util.ResourceBundle getResourceBundle(java.util.Locale locale)
Gets the resource bundle for the
given locale based on the resource bundle defined in the deployment descriptor
with resource-bundle tag or the inlined resources defined in the deployment
descriptor.
Specified by:
getInitParameter:
public java.lang.String getInitParameter(java.lang.String name)
Returns a
String containing the value of the named initialization parameter, or null if
the parameter does not exist.
Specified
by:
getInitParameterNames:
public java.util.Enumeration getInitParameterNames()
Returns the names of the portlet
initialization parameters as an Enumeration of String objects, or an empty
Enumeration if the portlet has no initialization parameters.
Specified by: