org.apache.tapestry.engine
Class RequestCycle

java.lang.Object
  org.apache.tapestry.engine.RequestCycle

All Implemented Interfaces:

ChangeObserver, IRequestCycle

public class RequestCycle
extends Object
implements IRequestCycle, ChangeObserver

Provides the logic for processing a single request cycle. Provides access to the engine and the RequestContext.

Author:

Howard Lewis Ship

Constructor Summary

RequestCycle(IEngine engine, RequestContext requestContext, IEngineService service, IMonitor monitor)
Standard constructor used to render a response page.

Method Summary

void	activate(IPage page) Sets the active page for the request.
void	activate(String name) A convienience for invoking IRequestCycle.activate(IPage).
void	cleanup() Called at the end of the request cycle (i.e., after all responses have been sent back to the client), to release all pages loaded during the request cycle.
void	commitPageChanges() Invokes IPageRecorder.commit() on each page recorder loaded during the request cycle (even recorders marked for discard).
void	discardPage(String name) Finds the page and its page recorder, creating the page recorder if necessary.
String	encodeURL(String URL) Passes the String through HttpServletResponse.encodeURL(java.lang.String), which ensures that the session id is encoded in the URL (if necessary).
Object	getAttribute(String name) Retrieves a previously stored attribute, returning null if not found.
IEngine	getEngine() Returns the engine which is processing this request cycle.
IMonitor	getMonitor()
String	getNextActionId() Returns the next action id.
IPage	getPage() Identifies the active page, the page which will ultimately render the response.
IPage	getPage(String name) Gets the page from the engines's IPageSource.
protected IPageRecorder	getPageRecorder(String name) Returns the page recorder for the named page.
RequestContext	getRequestContext()
IEngineService	getService() Returns the service which initiated this request cycle.
Object[]	getServiceParameters() Returns parameters previously stored by IRequestCycle.setServiceParameters(Object[]).
boolean	isRewinding() Returns true if the context is being used to rewind a prior state of the page.
boolean	isRewound(IComponent component) Checks to see if the current action id matches the target action id.
void	observeChange(ObservedChangeEvent event) For pages without a page recorder, we're the change observer.
void	removeAttribute(String name) Removes a previously stored attribute, if one with the given name exists.
void	renderPage(IMarkupWriter writer) Renders the page by invoking IPage.renderPage(IMarkupWriter, IRequestCycle).
void	rewindForm(IForm form, String targetActionId) Rewinds an individual form by invoking IForm.rewind(IMarkupWriter, IRequestCycle).
void	rewindPage(String targetActionId, IComponent targetComponent) Rewinds the page by invoking IPage.renderPage(IMarkupWriter, IRequestCycle).
void	setAttribute(String name, Object value) Allows a temporary object to be stored in the request cycle, which allows otherwise unrelated objects to communicate.
void	setPage(IPage value) Sets the page to be rendered.
void	setPage(String name) Sets the page to be rendered.
void	setServiceParameters(Object[] serviceParameters) Invoked by a service to store an array of application-specific parameters.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

RequestCycle

public RequestCycle(IEngine engine,
                    RequestContext requestContext,
                    IEngineService service,
                    IMonitor monitor)

Standard constructor used to render a response page.

Method Detail

cleanup

public void cleanup()

Called at the end of the request cycle (i.e., after all responses have been sent back to the client), to release all pages loaded during the request cycle.

Specified by:

cleanup in interface IRequestCycle

getService

public IEngineService getService()

Description copied from interface: IRequestCycle

Returns the service which initiated this request cycle. This may return null (very early during the request cycle) if the service has not yet been determined.

Specified by:

getService in interface IRequestCycle

encodeURL

public String encodeURL(String URL)

Description copied from interface: IRequestCycle

Passes the String through HttpServletResponse.encodeURL(java.lang.String), which ensures that the session id is encoded in the URL (if necessary).

Specified by:

encodeURL in interface IRequestCycle

getEngine

public IEngine getEngine()

Description copied from interface: IRequestCycle

Returns the engine which is processing this request cycle.

Specified by:

getEngine in interface IRequestCycle

getAttribute

public Object getAttribute(String name)

Description copied from interface: IRequestCycle

Retrieves a previously stored attribute, returning null if not found. Attributes allow components to locate each other; primarily they allow a wrapped component to locate a component which wraps it.

Specified by:

getAttribute in interface IRequestCycle

getMonitor

public IMonitor getMonitor()

Specified by:

getMonitor in interface IRequestCycle

getNextActionId

public String getNextActionId()

Description copied from interface: IRequestCycle

Returns the next action id. ActionLink ids are used to identify different actions on a page (URLs that are related to dynamic page state).

Specified by:

getNextActionId in interface IRequestCycle

getPage

public IPage getPage()

Description copied from interface: IRequestCycle

Identifies the active page, the page which will ultimately render the response.

Specified by:

getPage in interface IRequestCycle

getPage

public IPage getPage(String name)

Gets the page from the engines's IPageSource.

Specified by:

getPage in interface IRequestCycle

See Also:

IEngine.getPageSource()

getPageRecorder

protected IPageRecorder getPageRecorder(String name)

Returns the page recorder for the named page. This may come from the cycle's cache of page recorders or, if not yet encountered in this request cycle, the IEngine.getPageRecorder(String, IRequestCycle) is invoked to get the recorder, if it exists.

getRequestContext

public RequestContext getRequestContext()

Specified by:

getRequestContext in interface IRequestCycle

isRewinding

public boolean isRewinding()

Description copied from interface: IRequestCycle

Returns true if the context is being used to rewind a prior state of the page. This is only true when there is a target action id.

Specified by:

isRewinding in interface IRequestCycle

isRewound

public boolean isRewound(IComponent component)
                  throws StaleLinkException

Description copied from interface: IRequestCycle

Checks to see if the current action id matches the target action id. Returns true only if they match. Returns false if there is no target action id (that is, during page rendering).

If theres a match on action id, then the component is compared against the target component. If there's a mismatch then a StaleLinkException is thrown.

Specified by:

isRewound in interface IRequestCycle

Throws:

StaleLinkException

removeAttribute

public void removeAttribute(String name)

Description copied from interface: IRequestCycle

Removes a previously stored attribute, if one with the given name exists.

Specified by:

removeAttribute in interface IRequestCycle

renderPage

public void renderPage(IMarkupWriter writer)

Renders the page by invoking IPage.renderPage(IMarkupWriter, IRequestCycle). This clears all attributes.

Specified by:

renderPage in interface IRequestCycle

rewindForm

public void rewindForm(IForm form,
                       String targetActionId)

Rewinds an individual form by invoking IForm.rewind(IMarkupWriter, IRequestCycle).

The process is expected to end with a RenderRewoundException. If the entire page is renderred without this exception being thrown, it means that the target action id was not valid, and a ApplicationRuntimeException is thrown.

This clears all attributes.

Specified by:

rewindForm in interface IRequestCycle

Since:

1.0.2

rewindPage

public void rewindPage(String targetActionId,
                       IComponent targetComponent)

Rewinds the page by invoking IPage.renderPage(IMarkupWriter, IRequestCycle).

The process is expected to end with a RenderRewoundException. If the entire page is renderred without this exception being thrown, it means that the target action id was not valid, and a ApplicationRuntimeException is thrown.

This clears all attributes.

Specified by:

rewindPage in interface IRequestCycle

See Also:

IAction

setAttribute

public void setAttribute(String name,
                         Object value)

Description copied from interface: IRequestCycle

Allows a temporary object to be stored in the request cycle, which allows otherwise unrelated objects to communicate. This is similar to HttpServletRequest.setAttribute(), except that values can be changed and removed as well.

This is used by components to locate each other. A component, such as Body, will write itself under a well-known name into the request cycle, and components it wraps can locate it by that name.

Specified by:

setAttribute in interface IRequestCycle

setPage

public void setPage(IPage value)

Description copied from interface: IRequestCycle

Sets the page to be rendered. This is called by a component during the rewind phase to specify an alternate page to render during the response phase.

Specified by:

setPage in interface IRequestCycle

setPage

public void setPage(String name)

Description copied from interface: IRequestCycle

Sets the page to be rendered. This is called by a component during the rewind phase to specify an alternate page to render during the response phase.

Specified by:

setPage in interface IRequestCycle

commitPageChanges

public void commitPageChanges()

Invokes IPageRecorder.commit() on each page recorder loaded during the request cycle (even recorders marked for discard).

Specified by:

commitPageChanges in interface IRequestCycle

See Also:

IPageRecorder.commit()

observeChange

public void observeChange(ObservedChangeEvent event)

For pages without a page recorder, we're the change observer. If such a page actually emits a change, then we'll obtain a new page recorder from the engine, set the recorder as the page's change observer, and forward the event to the newly created recorder. In addition, the new page recorder is remembered so that it will be committed by commitPageChanges().

Specified by:

observeChange in interface ChangeObserver

discardPage

public void discardPage(String name)

Finds the page and its page recorder, creating the page recorder if necessary. The page recorder is marked for discard regardless of its current state.

This may make the application stateful even if the page recorder does not yet exist.

The page recorder will be discarded at the end of the current request cycle.

Specified by:

discardPage in interface IRequestCycle

Since:

2.0.2

getServiceParameters

public Object[] getServiceParameters()

Description copied from interface: IRequestCycle

Returns parameters previously stored by IRequestCycle.setServiceParameters(Object[]).

Through release 2.1, the return type was String[]. This is an incompatible change in 2.2.

Specified by:

getServiceParameters in interface IRequestCycle

Since:

2.0.3

setServiceParameters

public void setServiceParameters(Object[] serviceParameters)

Description copied from interface: IRequestCycle

Invoked by a service to store an array of application-specific parameters. These can later be retrieved (typically, by an application-specific listener method) by invoking IRequestCycle.getServiceParameters().

Through release 2.1, parameters was of type String[]. This is an incompatible change in 2.2.

Specified by:

setServiceParameters in interface IRequestCycle

Since:

2.0.3

See Also:

DirectService

activate

public void activate(String name)

Description copied from interface: IRequestCycle

A convienience for invoking IRequestCycle.activate(IPage). Invokes IRequestCycle.getPage(String) to get an instance of the named page.

Specified by:

activate in interface IRequestCycle

Since:

3.0

activate

public void activate(IPage page)

Description copied from interface: IRequestCycle

Sets the active page for the request. The active page is the page which will ultimately render the response. The activate page is typically set by the service. Frequently, the active page is changed (from a listener method) to choose an alternate page to render the response).

IPage.validate(IRequestCycle) is invoked on the page to be activated. PageRedirectException is caught and the page specified in the exception will be the active page instead (that is, a page may "pass the baton" to another page using the exception). The new page is also validated. This continues until a page does not throw PageRedirectException.

Validation loops can occur, where page A redirects to page B and then page B redirects back to page A (possibly with intermediate steps). This is detected and results in an ApplicationRuntimeException.

Specified by:

activate in interface IRequestCycle

Since:

3.0

toString

public String toString()

Overrides:

toString in class Object

Since:

3.0