12.4 Application-Specific Database Actions

You can use the JSTL database actions described in this chapter to develop many types of interesting web applications, such as product catalog interfaces, employee directories, or online billboards, without being a Java programmer. These types of applications account for a high percentage of the web applications developed today. But at some level of complexity, putting SQL statements directly in the web pages can become a maintenance problem. The SQL statements represent business logic, and for more complex applications, business logic is better developed as separate Java classes.

For a complex application, it may be better to use application-specific custom actions instead of the JSTL database actions described in this chapter. For example, all the generic database actions in Example 12-1, to SELECT and then INSERT or UPDATE the database, can be replaced with one application-specific action like this:

<myLib:saveEmployeeInfo dataSource="${example}" />

Part III, especially Chapter 24, describes how you can develop this type of custom action. Besides making it easier for the page author to deal with, the beauty of using an application-specific custom action is that it lets you evolve the application behind the scene. Initially, this action can be implemented so it uses JDBC to access the database directly, similar to how the JSTL actions work. But at some point it may make sense to migrate the application to an Enterprise JavaBeans architecture, perhaps to support other types of clients than web browsers. The action can then be modified to interact with an Enterprise JavaBeans component instead of accessing the database directly. From the JSP page author's point of view, it doesn't matter; the custom action is still used exactly the same way.

Another approach is to use a servlet for all database processing and only use JSP pages to show the result. You will find an example of this approach in Chapter 19.