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The Data Accessor pattern has the following consequences:


  • Clean application code— Application code that is replete with data access details is difficult to read and maintain. Application logic tends to become obscured by the many calls necessary to do even simple database calls. When an application uses a well-designed data accessor abstraction that exposes logical database operations, its code can focus more on its own business logic.

  • Adoption of new database features or platforms— When physical data access code is spread throughout a system, it is hard to add support for new features or platforms because it involves searching the entire code base and replacing or adding new calls where necessary. This process is tedious and error-prone. When a data accessor implementation encapsulates physical data access code, you only have one isolated component to enhance.

  • Incorporation of optimization strategies— Data access code usually is a primary analysis focal point when tuning an application's performance. Data access code is a common bottleneck source and simple optimizations often have significant effects. When data access code is spread across a system, it requires much more effort to apply and measure optimizations because you must repeat their implementations multiple times. When you encapsulate all physical data access code within a data accessor implementation, you can incorporate an optimization strategy once and it immediately applies across the entire system.

  • Swappable physical data access implementations— You can swap among multiple data accessor implementations without changing application code. This enables you to conveniently support multiple, diverse database platforms and technologies.


  • Limits application control of data access— Application code is limited to the logical operations defined by a data accessor abstraction. When a data accessor abstraction is not well-designed or versatile enough for an application's data access requirements, the application code may resort to unnatural or awkward workarounds that ultimately lead to unexpected results.

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