Adapter Pattern in Object-Oriented Programming Languages

Adapter Pattern in Object-Oriented Programming Languages

An adapter is a piece of hardware or software that connects incompatible devices. It may change one kind of input to another, like a USB to headphone adapter, or it can convert voltage, transmission protocol or even physical shape. Power adapters, for example, are used to make plugs of different shapes fit in foreign electrical outlets, allowing your US-style charger to power up your European-style laptop.

The term "adapter" also refers to programs that enable the integration of legacy applications with more modern ones, particularly those of a different system or technology. These programs are often referred to as adapter programs, application integration software or middleware. Depending on the specific use, they can be extremely sophisticated, performing such functions as transforming data or interacting with an enterprise information system (EIS). They can also be very thin and only "wrap" a native application interface, exposing another more standard one for applications to access.

Adapter programs are very popular for enabling backward compatibility in IT infrastructures, where there are existing applications and integrations that have been built using a previous version of an API or software platform. By providing a way for them to work with the newer system, they can ensure that these applications are not broken when an update is released.

There are several ways to implement the adapter pattern in object-oriented programming languages. The simplest is to create an adapter class that wraps the incompatible object and exposes a compatible interface that other classes can use. The class adapter can then be used by both the old and new classes, resulting in seamless collaboration that would not have been possible otherwise.

Another common adapter pattern involves the use of a bridge class that translates calls from the client into calls to the service. This type of adapter can be useful when working with 3rd-party or legacy code that doesn't have a clean, consistent interface. By creating an adapter class that encapsulates the incompatible class and makes it call the bridge, you can avoid having to create new child classes that add features that the original class didn't have, which could lead to messy and hard-to-maintain code.

A third approach to the adapter pattern is to simply add a method to the base class that will allow it to support incompatible interfaces. This method is often referred to as the decorator pattern. The base class can then use this function to decorate the appropriate methods, enabling it to adapt to different kinds of incompatible interfaces.

Adapters are commonly used in many areas of IT, including database management systems, enterprise application integrations and business process flows. Typically, the adapter program performs a number of functions, such as identifying events and changing data structures to match those in the target database or integration system. This allows it to communicate with the system more effectively, and it is often possible to use adapters with a range of different databases or integration platforms, extending the system's functionality without having to modify the existing business logic.