Guide to the Catalog J2EE

To help you effectively understand and use the J2EE patterns in the catalog, we suggest that you familiarize yourself with this section before reading the individual patterns. Here we introduce the pattern terminology and explain our use of the Unified Modeling Language(UML), stereotypes, and the pattern template. In short, we explain how to use these patterns. We also provide a high-level roadmap to the patterns in the catalog.


Players in the enterprise computing area, and particularly establishments using Java-based systems, have incorporated a number of terms and acronyms into their language. While many readers are familiar with these terms, sometimes their use varies from one setting to another. To avoid misunderstandings and to keep things consistent, we define in Table 4 how we use these terms and acronyms.



Use of UML

We have used UML extensively in the pattern catalog, particularly as follows:

  • Class diagrams. We use the class diagrams to show the structure of the pattern solution and the structure of the implementation strategies. This provides the static view of the solution.
  • Sequence (or Interaction) diagrams. We use these diagrams to show the interactions between different participants in a solution or a strategy. This provides the dynamic view of the solution.
  • Stereotypes. We use stereotypes to indicate different types of objects and roles in the class and interaction diagrams. The list of stereotypes and their meanings is included in Table 5.

Each pattern in the pattern catalog includes a class diagram that shows the structure of the solution and a sequence diagram that shows the interactions for the pattern. In addition, patterns with multiple strategies use class and sequence diagrams to explain each strategy.

UML Stereotypes

While reading the patterns and their diagrams, you will encounter certain stereotypes. Stereotypes are terms coined or used by designers and architects. We created and used these stereotypes in order to present the diagrams in a concise and easy to understand manner. Note that some of the stereotypes relate to the terminology explained in the previous section.

UML Stereotypes

UML Stereotypes

Pattern Template

The J2EE patterns are all structured according to a defined pattern template. The pattern template consists of sections presenting various attributes for a given pattern. You'll also notice that we've tried to give each J2EE pattern a descriptive pattern name. While it is difficult to fully encompass a single pattern in its name, the pattern names are intended to provide sufficient insight into the function of the pattern. Just as with names in real life, those assigned to patterns affect how the reader will interpret and eventually use that pattern.

We have adopted a pattern template that consists of the following sections:

  • Context: Sets the environment under which the pattern exists.
  • Problem: Describes the design issues faced by the developer.
  • Forces: Lists the reasons and motivations that affect the problem and the solution. The list of forces highlights the reasons why one might choose to use the pattern and provides a justification for using the pattern.
  • Solution: Describes the solution approach briefly and the solution elements in detail. The solution section contains two subsections:
  • Structure: Uses UML class diagrams to show the basic structure of the solution. The UML Sequence diagrams in this section present the dynamic mechanisms of the solution. There is a detailed explanation of the participants and collaborations.
  • Strategies: Describes different ways a pattern may be implemented.
  • Consequences: Here we describe the pattern trade-offs. Generally, this section focuses on the results of using a particular pattern or its strategy, and notes the pros and cons that may result from the application of the pattern.
  • Sample Code: This section includes example implementations and code listings for the patterns and the strategies.
  • Related Patterns: This section lists other relevant patterns in the J2EE Pattern Catalog or from other external resources, such as the GoF design patterns. For each related pattern, there is a brief description of its relationship to the pattern being described.
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