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In the field of programming a data transfer object (DTO [1] [2]) is an object that carries data between processes. The motivation for its use is that communication between processes is usually done resorting to remote interfaces (e.g., web services), where each call is an expensive operation. [ 2 ]
All details of storage are hidden from the rest of the application (see information hiding). Unit testing code is facilitated by substituting a test double for the DAO in the test, thereby making the tests independent of the persistence layer. In the context of the Java programming language, DAO can be implemented in various ways. This can ...
If the data access layer supports multiple database types, the application becomes able to use whatever databases the DAL can talk to. In either circumstance, having a data access layer provides a centralized location for all calls into the database, and thus makes it easier to port the application to other database systems (assuming that 100% ...
A sample UML class diagram for the adapter design pattern. [5] In the above UML class diagram, the client class that requires a target interface cannot reuse the adaptee class directly because its interface doesn't conform to the target interface. Instead, the client works through an adapter class that implements the target interface in terms ...
Computer science commonly presents levels (or, less commonly, layers) of abstraction, wherein each level represents a different model of the same information and processes, but with varying amounts of detail. Each level uses a system of expression involving a unique set of objects and compositions that apply only to a particular domain.
Object is the base class that provides common methods for all objects; "an object" is an integer, or a widget, or a Car, etc. Class is the base of the metaclasses that provides common methods for all classes (though it is not a metaclass itself); "a class" is something like Integer, or Widget, or Car, etc.
The model is an interface defining the data to be displayed or otherwise acted upon in the user interface. The view is a passive interface that displays data (the model) and routes user commands to the presenter to act upon that data. The presenter acts upon the model and the view. It retrieves data from repositories (the model), and formats it ...
In computer programming, the proxy pattern is a software design pattern.A proxy, in its most general form, is a class functioning as an interface to something else.The proxy could interface to anything: a network connection, a large object in memory, a file, or some other resource that is expensive or impossible to duplicate.