Service To Worker

See Core J2EE Patterns, 2nd Edition for full description of this pattern and its strategies.

Problem

You want to perform core request handling and invoke business logic before control is passed to the view.

Forces

• You want specific business logic executed to service a request in order to retrieve content that will be used to generate a dynamic response.
• You have view selections which may depend on responses from business service invocations.
• You may have to use a framework or library in the application.

Solution

Use Service to Worker to centralize control and request handling to retrieve a presentation model before turning control over to the view. The view generates a dynamic response based on the presentation model.

Class Diagram

Sequence Diagram

Strategies

• Servlet Front Strategy
• JSP Front Strategy
• Template-Based View Strategy
• Controller-Based View Strategy
• JavaBean Helper Strategy
• Custom Tag Helper Strategy
• Dispatcher in Controller Strategy

Consequences

• Centralizes control and improves modularity, reusability, and maintainability
• Improves role separation

Related Patterns

• Front Controller, Application Controller, and View Helper
  Service to Worker is a controller-centric architecture, highlighting a Front Controller. The Front Controller delegates to an Application Controller for navigation and dispatch, then to view and helpers.
• Composite View
  The view can be a Composite View.
• Business Delegate
  A Business Delegate is used to hide any remote semantics of the business service.
• Dispatcher View
  Dispatcher View is a view-centric architecture, where business processing is done after control is passed to the view.
• Business Delegate
  A Business Delegate reduces the coupling between a helper object and a remote business service, upon which the helper object can invoke.

Excerpted from Core J2EE Patterns, 2nd Edition. See the book for full description of the pattern including class diagrams, sequence diagrams and sample code.