Create 'Filter's

This section explains how to customzie Filter creation with PageServlet.

Overview

Class diagram

Class diagram in this section is shown below:

Class diagram (click for large figure)

Classes which you must define are colored, and other are already defined.

Class names

In this tutorial, abbreviated class names are used. Complete names are shown below.

Classes of PageMixer framework

Tutorial specific classes

Purpose of customization

Separating Filter creation from HTTP response renderring allows you to:

• reuse same creation logic in Servlets easily
• choose creation logic not only at compilation but also at configuration
• and so on

Implement Filter.Factory

PageMixer provides "FilterFactory" for customization of Filter creation.

But in fact, Filter which FilterFactory default implementation create directly is only FilterPipeline. It pushes Filter created by "Filter.Factory"s, which are registered to itself, into FilterPipeline.

Filter.Factory has the method to accept creation request as shown below.

public Filter create(ConsumerContext context)

You can get runtime information (e.g.: Servlet/web application initialization parameter) via specified ConsumerContext to create Filter.

Implementation example is shown below.

public Filter create(ConsumerContext context){
    return new CommonFilter();
}

It is good idea to define Filter.Factory implementation classes as inner class of each custom Filter classes for maintenance.

Please see API document for detail to implement Filter.Factory and/or override FilterFactory.

Configuration

Parameters for base class

FilterFactory accepts Servet initialize parameter(s) shown below:

Parameter to use choosen class

To use your custom FilterFactory, you should specify "servlet.filterFactory" Servlet init-param in deployment descriptor as shown below.

<init-param>
  <param-name>
    servlet.filterFactory
  </param-name>
  <param-value>
    name of your custom FilterFactory
  </param-value>
</init-param>