Web Data Modules

Like standard data modules, Web data modules are a container for components from the palette. Data modules provide a design surface for adding, removing, and selecting components. The Web data module differs from a standard data module in the structure of the unit and the interfaces that the Web data module implements.

Use the Web data module as a container for components that are shared across your application. For example, you can put a dataset component in a data module and access the dataset from both:

a page module that displays a grid, and
a page module that displays an input form.

You can also use Web data modules to contain sets of components that can be used by several different Web server applications.

Structure of a Web data module unit

Standard data modules have a variable called a form variable, which is used to access the data module object. Web data modules replace the variable with a function, which is defined in a Web data module's unit and has the same name as the Web data module. The function's purpose is the same as that of the variable it replaces. WebSnap applications may be multi-threaded and may have multiple instances of a particular module to service multiple requests concurrently. Therefore, the function is used to return the correct instance.

The Web data module unit also registers a factory to specify how the module should be managed by the WebSnap application. For example, flags indicate whether to cache the module and reuse it for other requests or to destroy the module after a request has been serviced.