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From "Bob Schellink (JIRA)" <>
Subject [jira] Commented: (CLK-598) Add Page Interceptor facility
Date Sun, 24 Jan 2010 14:00:18 GMT


Bob Schellink commented on CLK-598:

Wonder if this functionality could be extended to a Control as well. In ClickClick I needed
something similar: the ability to "intercept" certain events to add Ajax functionality to
controls. Currently this is solved through a custom EventDispatcher that can fire listeners
beforeOnProcess and beforeResponse. However the idea of an interceptor is semantically more
correct than a listener for this scenario.

One issue with a ControlInterceptor is that we don't have full control over the control lifecycle.
For example, controls are created and added by the developer, not by the framework so we won't
be able to intercept all events such as onInit. However the more interesting interception
points are beforeOnProcess and beforeOnResponse.

> Add Page Interceptor facility
> -----------------------------
>                 Key: CLK-598
>                 URL:
>             Project: Click
>          Issue Type: New Feature
>          Components: core
>            Reporter: Malcolm Edgar
>             Fix For: 2.2.0
> Provide an application page interceptor /  listener facility into Click.  The concept
is to provide an extension point for code which can listener to key page events and also interrupt
normal page processing flow.
> Using this code which tends to be incorporated into Page superclasses can be refactored
into listener classes which can be reused in applications. This approach supports Page design
by composition, rather than through inheritance.
> Page listeners could be used for:
> * enforcing an application wide security polity, rather than using the Page#onSecurityCheck()
> * dependency injection, see CLK-581
> * support page performance profiling and logging
> The listener interface would be:
> public interface PageInterceptor {
>        boolean pageCreate(Class<? extends Page> pageClass, Context context);
>        boolean postCreate(Page page);
>        boolean preResponse(Page page);
>        void postDestroy(Page page);
> }
> Application page interceptor  classes would be defined in the click.xml configuration
file. Applications could defined multiple interceptor which would be executed sequentially
in the order in which there are defined.  Lnterceptor could have a scope /  lifecycle of request
(where by new instances are created for each page request, and are threadsafe), or application
(where by a single instance is created and used for all page requests).  interceptor can also
be configured to have properties which are set after creation.  This scope rules equates to
Spring prototype and singleton scopes.
> An example configuration is provided below:
>     <page-interceptor classname="com.mycorp.listener.ProfilingInterceptor"/>
>     <page-interceptor classname="com.mycorp.listener.SecurityInterceptor" scope="application">
>         <property name="notAthenticatedPath" value="/login.htm"/>
>         <property name="notAuthorizedPath" value="/not-authorized.htm"/>
>     </page-interceptor >

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