Task 4: Get Familiar with the Dependency Injection Pattern
The Dependency Injection pattern promotes loose coupling between a class and the objects it depends on. With the Dependency Injection pattern, you do not instantiate the dependencies explicitly in your class. Instead, a class gets the objects it requires from an outside source. With the Web Client Software Factory, you express dependencies declaratively in your class definition. In the declaration, you specify an interface; you do not specify a concrete implementation. This means you can easily replace the implementation of an object that a class depends on, without changing the source code of the class. This is especially useful if you want to be able to test your classes in isolation. The Composite Web Application Block includes a dependency injection framework based on ObjectBuilder that you can use to implement the Dependency Injection pattern in your application; this framework is used frequently throughout the software factory.
For more information about the Dependency Injection pattern, see “Dependency Injection” in Web Client Software Factory Help.
Task 5: Register the Service
In this task, you will register the EFT service that you implemented in earlier tasks. You must register the service before another object can use dependency injection to obtain a reference to the service. You can register services either as module services or as global services. Module services are services that can be consumed only by the module that registers it. Global services are services that are available to all the modules in the solution. In this task, you will register the electronic funds transfer service as a module service.
To register module services, you implement the AddModuleServices method of the module initialization class of your business module.
A module initialization class is a class that implements the IModuleInitializer interface. This class contains initialization code that runs when the Composite Web Application Block loads the module. This interface defines two methods, Load and Configure. You implement these methods to perform module initialization tasks, such as registering services or adding site map nodes to the site map. For more information about module loading and the IModuleInitializer interface, see “Modules” in Web Client Software Factory Help.