Inversion of Control - Examples

Examples

public class ServerFacade { public V respondToRequest(K request) { if (businessLayer.validateRequest(request)) { DAO.getData(request); return Aspect.convertData(request); } return null; } }

This basic outline in Java gives an example of code following the IoC methodology. It is important, however, that in the ServerFacade a lot of assumptions are made about the data returned by the data access object (DAO).

Although all these assumptions might be valid at some time, they couple the implementation of the ServerFacade to the DAO implementation. Designing the application in the manner of inversion of control would hand over the control completely to the DAO object. The code would then become

public class ServerFacade { public V respondToRequest(K request, DAO dao) { return dao.getData(request); } }

The example shows that the way the method respondToRequest is constructed determines if IoC is used. It is the way that parameters are used that define IoC. This resembles the message-passing style that some object-oriented programming languages have been using.

Read more about this topic:  Inversion Of Control

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