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Anemic domain model
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Anemic domain model
The anemic domain model is described as a programming anti-pattern where the domain objects contain little or no business logic like validations, calculations, rules, and so forth. The business logic is thus baked into the architecture of the program itself, making refactoring and maintenance more difficult and time-consuming.
This anti-pattern was first described by Martin Fowler, who considers the practice an anti-pattern. He says:
The fundamental horror of this anti-pattern is that it's so contrary to the basic idea of object-oriented designing; which is to combine data and process together. The anemic domain model is just a procedural style design, exactly the kind of thing that object bigots like me ... have been fighting since our early days in Smalltalk. What's worse, many people think that anemic objects are real objects, and thus completely miss the point of what object-oriented design is all about.
In an anemic domain design, business logic is typically implemented in separate classes which transform the state of the domain objects. Fowler calls such external classes transaction scripts. This pattern is a common approach in Java applications, possibly encouraged by technologies such as early versions of EJB's Entity Beans, as well as in .NET applications following the Three-Layered Services Application architecture where such objects fall into the category of "Business Entities" (although Business Entities can also contain behavior).
Fowler describes the transaction script pattern thus:
Most business applications can be thought of as a series of transactions. A transaction may view some information as organized in a particular way, another will make changes to it. Each interaction between a client system and a server system contains a certain amount of logic. In some cases this can be as simple as displaying information in the database. In others it may involve many steps of validations and calculations. A Transaction Script organizes all this logic primarily as a single procedure, making calls directly to the database or through a thin database wrapper. Each transaction will have its own Transaction Script, although common subtasks can be broken into subprocedures.
In his book "Patterns of Enterprise Application Architecture", Fowler noted that the transaction script pattern may be proper for many simple business applications, and obviates a complex OO-database mapping layer.
An anemic domain model might occur in systems that are influenced from Service-Oriented Architectures, where behaviour does not or tends to not travel, such as messaging/pipeline architectures, or SOAP/REST APIs. Architectures like COM+ and Remoting allow behaviour, but increasingly the web has favoured disconnected and stateless architectures.
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Anemic domain model
The anemic domain model is described as a programming anti-pattern where the domain objects contain little or no business logic like validations, calculations, rules, and so forth. The business logic is thus baked into the architecture of the program itself, making refactoring and maintenance more difficult and time-consuming.
This anti-pattern was first described by Martin Fowler, who considers the practice an anti-pattern. He says:
The fundamental horror of this anti-pattern is that it's so contrary to the basic idea of object-oriented designing; which is to combine data and process together. The anemic domain model is just a procedural style design, exactly the kind of thing that object bigots like me ... have been fighting since our early days in Smalltalk. What's worse, many people think that anemic objects are real objects, and thus completely miss the point of what object-oriented design is all about.
In an anemic domain design, business logic is typically implemented in separate classes which transform the state of the domain objects. Fowler calls such external classes transaction scripts. This pattern is a common approach in Java applications, possibly encouraged by technologies such as early versions of EJB's Entity Beans, as well as in .NET applications following the Three-Layered Services Application architecture where such objects fall into the category of "Business Entities" (although Business Entities can also contain behavior).
Fowler describes the transaction script pattern thus:
Most business applications can be thought of as a series of transactions. A transaction may view some information as organized in a particular way, another will make changes to it. Each interaction between a client system and a server system contains a certain amount of logic. In some cases this can be as simple as displaying information in the database. In others it may involve many steps of validations and calculations. A Transaction Script organizes all this logic primarily as a single procedure, making calls directly to the database or through a thin database wrapper. Each transaction will have its own Transaction Script, although common subtasks can be broken into subprocedures.
In his book "Patterns of Enterprise Application Architecture", Fowler noted that the transaction script pattern may be proper for many simple business applications, and obviates a complex OO-database mapping layer.
An anemic domain model might occur in systems that are influenced from Service-Oriented Architectures, where behaviour does not or tends to not travel, such as messaging/pipeline architectures, or SOAP/REST APIs. Architectures like COM+ and Remoting allow behaviour, but increasingly the web has favoured disconnected and stateless architectures.