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Sams Teach Yourself J2EE™ in 21 Days by Peter Roxburgh, Andy Longshaw, Debbie Law, Dan Haywood, Martin Bond

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The Move into the Second Tier

The move towards 2-tier systems was born from the desire to share data between multiple applications installed on different machines. To do this, a separate database server machine was required. Figure 1.2 shows how this is achieved. The application now consists of presentation and business logic. Data is accessed by connecting to a database on another machine. Any changes to the Data Access logic should not affect the Presentation or Business logic in the application.

Figure 1.2. 2-tier scenario.

As indicated by Figure 1.2, splitting out Data Access Logic into a second tier keeps the data access independent and can ...

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