Goals of an Enterprise Architecture (J2EE)

A well-designed Enterprise Architecture should meet the following goals.

Be robust

Enterprise software is important to an organization. Its users expect it to be reliable and bug-free. Hence we must understand and take advantage of those parts of J2EE that can help us build robust solutions and must ensure that we write quality code.

Be performing and scalable

Enterprise applications must meet the performance expectations of their users. They must also exhibit sufficient scalability - the potential for an application to support increased load, given appropriate hardware. Scalability is a particularly important consideration for Internet applications, for which it is difficult to predict user numbers and behavior. Understanding the J2EE infrastructure is essential for meeting both these goals. Scalability will typically require deploying multiple server instances in a cluster. Clustering is a complex problem requiring sophisticated application server functionality. We must ensure that our applications are designed so that operation in a cluster is efficient.

Take advantage of OO design principles

OO design principles offer proven benefits for complex systems. Good OO design practice is promoted by the use of proven design patterns - recurring solutions to common problems. It's vital that we use J2EE to implement OO designs, rather than let our use of J2EE dictate object design. Today there's a whole "J2EE patterns" industry. While many "J2EE patterns" are valuable, classic (non-technology-specific) design patterns are more so, and still highly relevant to J2EE.

Avoid unnecessary complexity

Practitioners of Extreme Programming (XP) advocate doing "the simplest thing that could possibly work". We should be wary of excessive complexity that may indicate that application architecture isn't working. Due to the range of components on offer, it's tempting to over-engineer J2EE solutions, accepting greater complexity for capabilities irrelevant to the business requirements. Complexity adds to costs throughout the software lifecycle and thus can be a serious problem. On the other hand, thorough analysis must ensure that we don't have a naïve and simplistic view of requirements.

Be maintainable and extensible

Maintenance is by far the most expensive phase of the software lifecycle. It's particularly important to consider maintainability when designing J2EE solutions, because adopting J2EE is a strategic choice. J2EE applications are likely to be a key part of an organization's software mix for years, and must be able to accommodate new business needs.

Maintainability and extensibility depend largely on clean design. We need to ensure that each component of the application has a clear responsibility, and that maintenance is not hindered by tightly-coupled components.

Be delivered on time

Productivity is a vital consideration, which is too often neglected when approaching J2EE.

Be easy to test

Testing is an essential activity throughout the software lifecycle. We should consider the implications of design decisions for ease of testing.

Promote reuse

Enterprise software must fit into an organization's long term strategy. Thus it's important to foster reuse, so that code duplication is minimized (within and across projects) and investment leveraged to the full. Code reuse usually results from good OO design practice, while we should also consistently use valuable infrastructure provided by the application server where it simplifies application code.

Support for multiple client types

There's an implicit assumption that J2EE applications always need to support multiple J2EE-technology client types, such as web applications, standalone Java GUIs using Swing or other windowing systems or Java applets. However, such support is often unnecessary, as "thin" web interfaces are being more and more widely used, even for applications intended for use within an organization (ease of deployment is one of the major reasons for this).

Portability