Almost all modern Web-development frameworks follow the Model-View-Controller (MVC) design. Business logic and presentation are separated and a controller of logic flow coordinates requests from clients and actions taken on the server. This approach has become the de facto of Web development. The underlying mechanics of each framework are of course different, but the APIs that developers use to design and implement their Web applications are very similar. The difference also lies in the extensions that each framework provides, such as tag libraries, Java Server Faces, or Java Bean wrappers.
All frameworks use different techniques to coordinate the navigation within the Web application, such as the XML configuration file, java property files, or custom properties. All frameworks also differ in the way the controller module is implemented. For instance, EJBs may instantiate classes needed in each request, or Java reflection can be used to dynamically invoke an appropriate action classes. Also, frameworks may differ conceptually. For example, one framework may define the user request and response (and error) scenario, and another may only define a complete flow from one request to multiple responses and subsequent requests.
Java frameworks are similar in the way they structure data flow. After request, some action takes place on the application server, and some data populated objects are always sent to the JSP layer with the response. Data is then extracted from those objects, which could be simple classes with setter and getter methods, java beans, value objects, or some collection objects. Modern Java frameworks also simplify a developer's tasks by providing automatic Session tracking with easy APIs, database connection pools, and even database call wrappers. Some frameworks either provide hooks into other J2EE technologies, such as JMS (Java Messaging Service) or JMX, or have these technologies integrated. Server data persistence and logging also could be part of a framework.
Popular Web Frameworks
Apache Struts Framework
The Struts framework is an open-source product for building Web applications based on the model-view-controller (MVC) design paradigm. It uses and extends the Java Servlet API and was originally created by Craig McClanahan. In May 2000, it was donated to the Apache Foundation. It features a powerful custom tag library, tiled displays, form validation, and I18N (internationalization). Also, Struts supports a variety of presentation layers, including JSP, XML/XSLT, JavaServer Faces (JSF), and Velocity, as well as a variety of model layers, including JavaBeans and EJB.
The Spring Framework is a layered Java/J2EE application framework based on code published in Expert One-on-One J2EE Design and Development. The Spring Framework provides a simple approach to development that does away with numerous properties files and helper classes that litter projects. Key features of the Spring Framework include:
Powerful JavaBeans-based configuration management, applying Inversion-of-Control (IoC) principles.
A core bean factory, usable in any environment, from applets to J2EE containers.
Generic abstraction layer for database transaction management, allowing for pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues.
JDBC abstraction layer with a meaningful exception hierarchy.
Integration with Hibernate, DAO implementation support, and transaction strategies.
Hibernate is an object-relational mapping (ORM) solution for the Java language. It is also open source software, as is Struts, and is distributed under the LGPL. Hibernate was developed by a team of Java software developers around the world. It provides an easy to use framework for mapping an object-oriented domain model to a traditional relational database. It not only takes care of the mapping from Java classes to database tables (and from Java data types to SQL data types), but also provides data query and retrieval facilities and can significantly reduce development time otherwise spent with manual data handling in SQL and JDBC.
Hibernate's goal is to relieve the developer from a significant amount of common data persistence-related programming tasks. Hibernate adapts to the development process, whether it is started with a design from scratch or from a legacy database. Hibernate generates the SQL, and relieves the developer from manual result set handling and object conversion, and keeps the application portable to all SQL databases. It provides transparent persistence, the only requirement for a persistent class is a no-argument constructor.
There are more frameworks than I have described here, of course, both open-source and commercial, such as
WebWork - http://www.opensymphony.com/webwork/
Tapestry - http://jakarta.apache.org/tapestry/,
and many frameworks were in-house developed by extending some other MVC frameworks.
Enterprise Development Environments
Some of these frameworks became very popular within the Web developer Community and enterprise development space. As these frameworks matured into stable releases, commercial IDE (integrated development environment) toolmakers started to build support for them into their products. Some even went as far as to develop whole products based on the concepts of the framework. For example, BEA WebLogic Workshop is build around the Struts framework.Borland JBuilder has built-in support for Struts and features JSF and JSTL support as well.
The Eclipse platform became a very popular development tool, partly because of its plug-in base and partly because of its Web framework support. Numerous plug-ins to Eclipse or even entire distributions of Eclipse-based IDEs appeared. Many of the plug-ins were designed for Struts framework development, such as MyEclipse (www.myeclipse.org) or M7 (www.m7.com).
As the Web development arena continues to evolve its tools and programming methodologies, so will the Java application frameworks continue to grow. The future seems very bright for the Java Web-development frameworks.
End of Part III