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From "Malcolm Edgar (JIRA)" <>
Subject [jira] Created: (CLK-598) Provide Page Listener / Interceptor facility
Date Fri, 25 Dec 2009 21:56:29 GMT
Provide Page Listener / Interceptor facility

                 Key: CLK-598
             Project: Click
          Issue Type: New Feature
          Components: core
            Reporter: Malcolm Edgar
             Fix For: 2.2.0

Provide an application page listener / interceptor 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 PageListener {

       boolean pageCreate(Class<? extends Page> pageClass, Context context);

       boolean postCreate(Page page);

       boolean preResponse(Page page);

       void postDestroy(Page page);

Application page listeners classes would be defined in the click.xml configuration file. Applications
could defined multiple listeners which would be executed sequentially in the order in which
there are defined.  Listeners 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).  Listener 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-listener classname="com.mycorp.listener.PageProfilerListener/>

    <page-listener classname="com.mycorp.listener.SecurityPageListener" scope="application">
        <property name="notAthenticatedPath" value="/login.htm"/>
        <property name="notAuthorizedPath" value="/not-authorized.htm"/>


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