Assembling an Enterprise Servlet Using The Simplicity Enterprise Module Palette

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Modules add units of functionality to Enterprise Servlets. Each module is designed to perform some common task that Servlets may require. By selecting Modules that accomplish sub-tasks that your Servlet requires and dropping them into the Modules node of your servlet in the order that you wish to perform the associated tasks, you can often build an entire Servlet without having write any Java code at all. Once a Module has been dropped into the Module node of the Parts Tree, a new node will be created in the tree for that Module.

The property pages for the Module node and its sub-nodes provide interfaces that allow you to set up or customize the Module to accomplish the desired task. Although some Modules may have useful default values already selected in these property sheets, most Modules require that you select the appropriate options and enter the appropriate data into these property sheets before the Module can perform any useful task.

All Modules have at least one sub-node and may, optionally, have more sub-nodes. Selecting the top level Module node will change the contents of the Help area and properties sheet to the right of the tree in the Enterprise Composer. The Help area contains documentation describing the Module and its use.

The properties sheet of all Modules contains two text areas and four check boxes. These first text field can be used to change the name of the module. The next part of the property sheet is related to the behavior or the Module when an Error or Exception occurs in the Module. The comment is passed to the Error Handler and Exception Handler if an Error or Exception occurs. This can be used in these Methods to provide diagnostic information. The first two checkboxes determine whether or not to continue if an Error or Exception occurs in the Module. By default, Errors cause the execution of the primary code to halt and execution to pass on to the Error Handler. Exceptions, default to allow execution of the primary code to continue after the Exception Handler has completed. Finally, the last two checkboxes will show pre or post-processing code areas in the tree. These are areas where you can enter code which will be executed before or after the Module's main code executes, in the same scope as the Module. This allows the user to modify the behavior of Modules.

The properties node of every Module is different. In the case of simple Modules, the properties node may be the only sub-node of the Module. When the properties node is selected the Help area will generally have documentation on how to fill out the property sheet of the properties node. Similarly any other sub-nodes that the Module may have should have corresponding documentation in the Help area when those nodes are selected.