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Web DBForms

Author：Joachim Peer Joachim Peer is an independent J2EE developer. He holds a masters degree in Management Information Systems of Johannes Kepler University, Linz, Austria, with a focus in the fields of software engineering, multimedia application development and knowledge and process management. He is a Sun certified programmer for the Java 2 platform.

Many developers find themselves writing similar JSP and servlet code again and again when creating Web-based database applications. The open source project DbForms provides a solution that reduces the amount of coding to an absolute minimum.

This article gives an overview of DbForms and its concepts and features, and shows some code examples.

Introduction

DbForms is a Java-based Rapid Application Development (RAD) environment which enables developers to build Web-based database applications in a very short time and with very little effort. DbForms applications are built in a conceptually very similar manner to RAD database-building tools like Microsoft Access (for Windows-based applications) or Sybase PowerSite (for Web-based applications). The basic principle of these RAD-Tools could be described as "placing database-aware components and action elements on templates (forms) which get executed at runtime."

DbForms builds on top of Java Servlets 2.2 and Java Server Pages 1.1 technologies by Sun Microsystems. It makes extensive use of the JSP Tag Library extension introduced in the JSP 1.1 specification.

The project's homepage is located at and contains a complete user manual, several technical articles, source and binary distributions, online examples, a CVS, mailing lists, and lots of other information related to DbForms.

DbForms implements the concepts of the Model-View-Controller (MVC) design pattern. (See Design Patterns: Elements of Reusable Object-Oriented Software, Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, Addison Wesley, October 1994.) You do not need to provide any Controller-related code; just focus on defining the Model and creating the JSP view components of the application (mainly using DbForms custom tags).

The following discusses how Model, View and Controller interact in DbForms. The Model: Database Objects Described by Database Metadata

The use of DbForms is to perform operations on databases. The database tables accessed by a DbForms application must be declared in a XML configuration file (usually stored as WEB-INF/dbforms-config.xml), which is parsed and evaluated at Web-application startup time.

As shown in Listing 1, every table (or view) to be accessed by DbForms