JAVA EE: Business Delegate Design Pattern

Sunday, 29 September 2013

Business Delegate Design Pattern - KeyPoints

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What Is the Business Delegate Design Pattern?

The Business Delegate Design Pattern is a core Java EE architectural pattern used to decouple the presentation tier (such as UI clients, Servlets, or controllers) from the business tier (such as EJBs, JMS, or remote web services). By placing an intermediary layer between them, your client code avoids dealing directly with network protocols, remote lookup exceptions, or business API changes.

Essential Takeaways and Architecture

Decouples Presentation and Business Tiers: Shielding front-end classes from the complexities of underlying business services prevents changes in backend APIs from breaking UI code.
Centralizes Service Lookups: Works seamlessly with a Service Locator to resolve remote references (like JNDI lookups) in a single place.
Caches Business Service References: The delegate can cache resolved remote service objects, substantially cutting down costly network lookups and boosting overall response times.
Encapsulates Remote Exceptions: Converts low-level network or distributed lookup failures (like NamingException or RemoteException) into clean, presentation-friendly application exceptions.

Major Advantages for Developers

Maintainability: Updates or migrations in business tier technologies (e.g., migrating from EJB to REST/gRPC) require changes only within the delegate, leaving the presentation tier intact.
Performance Optimization: Client-side caching of business service stubs avoids redundant network overhead.
Cleaner Presentation Layer: Keeps user interface controllers focused strictly on UI formatting, validation, and rendering rather than distributed enterprise calls.