JavaServer Pages, Second Edition

JSP Bean Examples

In a JSP-based application, two types of beans are primarily used: value beans and utility beans. A value bean encapsulates all information about some entity, such as a user or a product. A utility bean performs some action, such as saving information in a database or sending email. Utility beans can use value beans as input or produce value beans as a result of an action.

If you develop beans for your application, you’re also preparing for migration to a full-blown J2EE application. The utility beans can be changed into proxies for one or more EJB session beans, acting as part of the Controller for the application.

Value beans may act as what’s called Value Objects in JavaSoft’s Designing Enterprise Applications With the Java 2 Platform, Enterprise Edition paper, also known as the J2EE Blueprints. In an EJB-based application, the application’s data is represented by EJB entity beans. Getting a property value from an EJB entity bean requires a remote call, consuming both system resources and bandwidth. Instead of making a remote call for each property value that is needed, the web component can make one remote call to an EJB session bean (possibly via a JSP utility bean) that returns all properties of interest packaged as a value bean. The web component can then get all the properties from the value bean with inexpensive local calls. The value bean can also act as cache in the web container to minimize remote calls even more and can combine information from multiple ...