What is Frame2?

Frame2 is a second-generation implementation of the JSP Model 2 web application architecture.
It builds on the prior art of frameworks such as Struts, WebMacro and Virtuas Solutions' TurboM2 Framework to present a highly configurable and modularized tool that supports the development of both web applications and web services using J2EE.
Frame2 users (that is, developers who build web applications and services) will use the Frame2 framework to integrate business assets with web-based user interfaces.
With Frame2, business assets may be used as-is, with no modification. The user interface components (JSPs, HTML, images, etc.) are bundled with the framework, configuration information, and user extensions for deployment in the J2EE servlet container.

The Frame2 Development Model

Frame2 presents a standard layered/n-tier model for development. Each layer contains code and configuration data specific to its purpose. These layers are intended to keep application and service development simple, reliable and sustainable.
The layers in the Frame2 model are as follows:

Client Presentation - Presentation code that executes on the client. This generally corresponds to Javascript placed into the HTML response. Javascript may be used to perform lightweight validation or to implement dynamic presentation features.
Server Presentation - Presentation code that executes on the server. This generally corresponds to JSP and custom tag code. Frame2 provides custom tags for seamlessly combining HTML with server data.
Application Controller - The controller acts as a mediator between the presentation layer and the application logic. Because the mapping of requests to application-specific logic and data lends itself to generic, data-driven implementations, the application controller is an ideal candidate for framework design. Packages such as Frame2 and Struts serve this role.
Application Logic - Application code that implements logic for the navigation and processing of user inputs (i.e. complicated validation or integrity checks). Application logic pertains to the behavior of the application with respect to user inputs.
Business Services or Model - Domain oriented data abstractions, services and models. These are separated from the application logic and have a high potential for reuse across different applications. They may be hosted in the same container as the application layers or hosted remotely.
Resource - Resources external to the application such as databases, messaging services, transaction managers, other remote facilities.

For web services, the layering corresponds to a similar model. The presentation layer is replaced with programmatic clients, which are often outside the realm of the service developer. Additionally application-level behaviors are simplified in comparison to web applications, often reduced to pass-through to the underlying business service.

Interposing an application controller between the client and application logic offers numerous advantages. Foremost is simplifying the work to develop web applications that have non-trivial navigation and processing rules. Complicated and rote programming tasks for managing the navigation rules, converting data from the HTTP requests, and data validation can be avoided through automation and configuration. Security measures can also be made uniform.

Configurability

Model 2 controllers intrinsically manage navigation concerns.
Frame2 provides a rich set of configuration features that combine easily with user-provided application logic. Through the configuration, users can define mappings between the client requests and the application components that process those requests, and between the outcomes of the processing to the views.
Within these configuration elements specification can be given to how to handle invalid inputs, cancellation requests, and errors generated by the application code of the framework itself.
In support of co-hosting both web applications and web services in the same deployment, the configuration information can be segregated between the HTTP and the XML processing streams.

Web Application Support

Frame2 provides a number of features for web application support.
At the server presentation layer it provides custom tags that extend the JSTL expression language to standard HTML tags as well as allowing internationalization without the need for learning or understanding new tag attributes.
At the controller layer, Frame2 gives a simplified programming model for creating and structuring application data and logic. Frame2 automatically populates JavaBeans with data from the HTTP request, validates the data, and then provide the data to the appropriate handlers for execution of the application logic.
To complement these features Frame2 interoperates with the J2EE security model to allow configurable role-based security for all requests made through the framework.

Web Service Support

Frame2 can be used with any JAX-RPC SOAP front-end (for example, Apache Axis or the Sun's JWSDP).
The web service features give the user broad latitude in how the SOAP request body is structured as well as how the response is generated.
Bodies may be processed as single or batch requests, with unmarshalling into JavaBeans automatically taken care of through JAXB technologies. Frame2 interoperates with JAXB to allow XML schema definitions to be automatically converted and validated as JavaBeans.
With a defined schema, developers can code application and business services without having to understand XML or SOAP; the code to the JavaBean representations of the SOAP bodies and Frame2 with JAXB manages conversion.

Simple API

Frame2 abstracts the transport and protocol layers to minimize the difficulty with learning and using complex technologies such as J2EE and SOAP.
Most development can be done in the application layer by reading and setting bean properties and exercising business services. The simple API in combination with the flexible configuration helps maintain good separation between the model, view and controller components.

Struts Differences

There are numerous feature-based comparisons to be made with Struts, the most popular open-source framework for building J2EE web applications.
From a framework design point of view, there are several key differences:

Frame2 abstracts the J2EE API and HTTP protocol away from the user-provided application code. Developers do not need detailed knowledge of either to be productive in the environment.
Frame2 more naturally models the interaction between the user interface or client and the server elements. Struts treats this as a procedure call, where the request data is an argument to a requested action. Frame2 unifies the request intent and data into an event which is sequentially processed by event handlers. This model is more common to user-oriented applications and more flexible with respect to developing and configuring reusable application components.
Frame2 minimizes the amount of wrapping of existing standard Java APIs. For example, no wrapping is provided for message formatting and resource bundle management is limited to what is necessary for the framework.
Frame2 places more emphasis on flexibility in the configuration of the application. Users have more options for setting application strategies through the configuration, and more options for organizing their application logic to be reused both within the web application and across applications.
Frame2 supports co-hosting both web applications and web services with reuse of data and logic components between the two. The web applications are supported through a traditional J2EE Model 2 architecture with a configurable controller. The web services are supported through interoperability of the same controller with SOAP front-ends such as Apache Axis or the Sun implementation of JAX-RPC.
Frame2 places more emphasis on using emerging technologies such as the JSTL/EL and JAXB. As such, it lacks compatibility with older developer kits and J2EE specifications; however, it takes advantage of technologies like the Expression Language (EL), which makes obsolete the elaborate and framework specific tag libraries provided by Struts.

The differences are all intended to simplify developing a web application by creating a simple but flexible API.