The logical architecture specified in the deployment scenario generally determines the scope of custom development work needed to implement a solution.
For some deployments, development might be quite extensive, requiring you to develop new business and presentation services from the beginning using J2EE components that run in an Application Server or Web Server environment. In such cases, you create a prototype of your solution and perform proof-of-concept testing before embarking on a full development effort.
For solutions that require extensive development, Sun Java Studio provides tools for programming distributed components or business services. Sun Java Studio simplifies the programming and testing of applications supported by the Java ES infrastructure.
In some situations, Java ES components might be integrated with legacy applications or third-party services. These integrations might involve existing directories or data services in the data tier or existing components in the business services tier. Integrating Java ES components with these systems might require migrating data or application code.
The J2EE platform provides a connector framework that lets you plug existing applications into the Application Server environment by developing J2EE resource adapters, and Message Queue provides a robust asynchronous messaging capability for integrating diverse applications.