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MIGRATING WEB 1.0 INTERFACES TO RIA

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PHP Middle Tier

PHP objects and scripts are less governed by specification than Java EE objects. Therefore, the form in

which a PHP middle tier exists could be quite varied. It could be within a container, like the Zend engine, or

it could live as objects on a PHP-enabled web server. The PHP code may be procedural or object

oriented.

Flex to PHP remoting options like the AMFPHP remoting library can be used to facilitate RPCs. However,

there is one possible obstacle to direct usage of the middle-tier methods. Not all PHP applications cleanly

demarcate between presentation logic and behavior, so directly consuming the data returned by PHP

methods in Flex may require additional parsing on the Flex side. In such situations, you may benefit from

following the preceding advice on making PHP generate XML or service-orienting the existing application.

Strategies to Port Framework-based Applications

As mentioned earlier, we pick two frameworks, Apache Struts and Ruby on Rails, and port them over to

use a Flex user interface. If you are planning to port applications of either of these two types, then this

section will give you a starting point in your endeavor. If your framework is not one of these two, then you

will still benefit indirectly, as the examples will give you some insight into the migration options at your

disposal.

Let’s rework an Apache Struts 1.x application to include a Flex user interface.

Apache Struts 1.x and Flex

First, take a look at Figure 12-16, which pictorially describes Apache Struts. Requests to an Apache

Struts–powered web application are intercepted by its front controller. The front controller routes requests

to appropriate action classes. The framework configuration and the request URL to action mapping are

accessed from the struts-config.xml file and the action mapping class instance. Action classes access

the middle-tier objects and the underlying data and then forward the output to a JSP. Alternatively, Apache

Tiles can be used to construct the views.

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Figure 12-16. Apache Struts—its front controller, action classes, action mapping, configuration, and form

bean

The preceding description is true for Apache Struts 1.x. Apache Struts 2.0 is a drastic overhaul of the

framework and is out of the scope of the current discussion.

A possible migration path from Apache Struts 1.x to Flex is to replace the View part of the Apache Struts

Model-View-Controller (MVC) structure. (In order to migrate smoothly, you need to make the following

modifications:

• Create a new Flex user interface.

• Invoke Apache Struts actions based on requests from Flex.

• Forward the output to a JSP that does not display the data but forwards the data in a format

that can be consumed by the Flex interface.

• Forward the error messages to a JSP that does not display the error messages but forwards

the data in a format that can be consumed by the Flex interface.