org.zkoss.zk.ui.util

Interface DesktopRecycle

All Known Implementing Classes:

DesktopRecycle

public interface DesktopRecycle

Used to recycle the desktop (Desktop). By recycling the desktop, we mean to re-use the same desktop for the same URI if applicable. For example, if an user navigates to other URL and navigates back, the application can re-use the same desktop (by implementing this interface). It is useful if the page takes a lot of time to prepare.

A typical implementation (such as DesktopRecycle) caches the desktop when beforeRemove(org.zkoss.zk.ui.Execution, org.zkoss.zk.ui.Desktop, int) is called, and then return it if beforeService(org.zkoss.zk.ui.Execution, java.lang.String) matches it.

Please refer to Performance Tips for more information.

Since:

5.0.0

Author:

tomyeh

Method Summary

Modifier and Type	Method and Description
void	afterRemove(Session sess, Desktop desktop) Called after a desktop is removed.
void	afterService(Desktop desktop) Called after the request is served.
boolean	beforeRemove(Execution exec, Desktop desktop, int cause) Called when the client asks the server to remove a desktop because of the user's navigating to other URL or refreshing the page.
Desktop	beforeService(Execution exec, java.lang.String uri) Called when an user requests the content of a page.

Method Detail

beforeRemove

boolean beforeRemove(Execution exec,
                     Desktop desktop,
                     int cause)

Called when the client asks the server to remove a desktop because of the user's navigating to other URL or refreshing the page.

The implementation can retrieve the request path by calling Desktop.getRequestPath().

Notice that, when the user refreshes a page, this method might be called after beforeService(org.zkoss.zk.ui.Execution, java.lang.String) is called (depending on the browser and networking). In other words, there is no way it is a brand-new request from a new window, or it is caused by user's refreshing.

Parameters:

exec - the current execution.

cause - the cause. It is reserved for the future extension.

Returns:

whether to recycle the desktop. If true is returned, the desktop won't be removed. It is the implementation's job to remove it if necessary.

afterRemove

void afterRemove(Session sess,
                 Desktop desktop)

Called after a desktop is removed. A desktop is removed for different reasons, such as a session timeout, and too many desktops (when the memory is running low). In other words, some desktops are removed directly and only afterRemove(org.zkoss.zk.ui.Session, org.zkoss.zk.ui.Desktop) is called.

The implementation has to remove the cached desktop, if any.

When this method is called, there might be no execution available (Executions.getCurrent() might return null).

Parameters:

sess - the session that the desktop belongs to. Notice that Desktop.getSession() might be null when this method is called since it is destroyed.

desktop - the desktop to remove

beforeService

Desktop beforeService(Execution exec,
                      java.lang.String uri)

Called when an user requests the content of a page. To reuse a desktop, this method has to return the desktop to reuse.

Parameters:

exec - the execution. It doesn't not associated with a desktop, and used only for accessing the request and response.

uri - the request URI. It is a combination of Desktop.getRequestPath() and Desktop.getQueryString(). For example, if Desktop.getRequestPath() and Desktop.getQueryString() are "/foo.zul" and "abc=1", then this parameter is "/foo.zul?abc=1".

Returns:

the desktop to re-use. If null is returned, ZK Loader will create a desktop as if this interface is not installed.

afterService

void afterService(Desktop desktop)

Called after the request is served.

The implementation usually does nothing in this method, unless it wants to re-use it no matter if the same user might open two or more windows to visit the same URL.

When this method is called, there might be no execution available (Executions.getCurrent() might return null).