Interface Portlet
- All Known Implementing Classes:
GenericPortlet
Portlet
interface is used by the portlet container to
invoke the portlets. Every portlet has to implement this interface,
either by directly implementing it, or by using an existing class
implementing the Portlet interface.
A portlet is a Java technology-based web component. It is managed by the portlet container and processes requests and generates dynamic content as response. Portlets are used by portals as pluggable user interface components.
The content generated by a portlet is called a fragment. A fragment is a piece of markup (e.g. HTML, XHTML, WML) adhering to certain rules and can be aggregated with other fragments into a complete document. The content of a portlet is normally aggregated with the content of other portlets into the portal page.
The portlet container instanciates portlets, manages their lifecycle and invoking them to process requests. The lifecycle consists of:
- initializing the portlet using using the
init
method - request processsing
- taking the portlet out of service using the
destroy
method
Request processing is divided into two types:
- action requests handled through the
processAction
method, to perform actions targeted to the portlet - render requests handled through the
render
method, to perform the render operation
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Method Summary
Modifier and TypeMethodDescriptionvoid
destroy()
Called by the portlet container to indicate to a portlet that the portlet is being taken out of service.void
init
(PortletConfig config) Called by the portlet container to indicate to a portlet that the portlet is being placed into service.void
processAction
(ActionRequest request, ActionResponse response) Called by the portlet container to allow the portlet to process an action request.void
render
(RenderRequest request, RenderResponse response) Called by the portlet container to allow the portlet to generate the content of the response based on its current state.
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Method Details
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init
Called by the portlet container to indicate to a portlet that the portlet is being placed into service.The portlet container calls the
init
method exactly once after instantiating the portlet. Theinit
method must complete successfully before the portlet can receive any requests.The portlet container cannot place the portlet into service if the
init
method- Throws a
PortletException
- Does not return within a time period defined by the portlet container.
- Parameters:
config
- aPortletConfig
object containing the portlet's configuration and initialization parameters- Throws:
PortletException
- if an exception has occurred that interferes with the portlet's normal operation.UnavailableException
- if the portlet cannot perform the initialization at this time.
- Throws a
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processAction
void processAction(ActionRequest request, ActionResponse response) throws PortletException, IOException 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 theRenderResponse.createActionURL()
method.Typically, in response to an action request, a portlet updates state based on the information sent in the action request parameters. In an action the portlet may:
- issue a redirect
- change its window state
- change its portlet mode
- modify its persistent state
- set render parameters
A client request triggered by an action URL translates into one action request and many render requests, one per portlet in the portal page. The action processing must be finished before the render requests can be issued.
- Parameters:
request
- the action requestresponse
- the action response- Throws:
PortletException
- if the portlet has problems fulfilling the requestUnavailableException
- if the portlet is unavailable to process the action at this timePortletSecurityException
- if the portlet cannot fullfill this request because of security reasonsIOException
- if the streaming causes an I/O problemIOException
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render
Called by the portlet container to allow the portlet to generate the content of the response based on its current state.- Parameters:
request
- the render requestresponse
- the render response- Throws:
PortletException
- if the portlet has problems fulfilling the rendering requestUnavailableException
- if the portlet is unavailable to perform render at this timePortletSecurityException
- if the portlet cannot fullfill this request because of security reasonsIOException
- if the streaming causes an I/O problem
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destroy
void destroy()Called by the portlet container to indicate to a portlet that the portlet is being taken out of service.Before the portlet container calls the destroy method, it should allow any threads that are currently processing requests within the portlet object to complete execution. To avoid waiting forever, the portlet container can optionally wait for a predefined time before destroying the portlet object.
This method enables the portlet to do the following:
- clean up any resources that it holds (for example, memory, file handles, threads)
- make sure that any persistent state is synchronized with the portlet current state in memory.
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