What Is an Enterprise Bean? (original) (raw)
2. Using the Tutorial Examples
3. Getting Started with Web Applications
4. JavaServer Faces Technology
7. Using JavaServer Faces Technology in Web Pages
8. Using Converters, Listeners, and Validators
9. Developing with JavaServer Faces Technology
10. JavaServer Faces Technology: Advanced Concepts
11. Using Ajax with JavaServer Faces Technology
12. Composite Components: Advanced Topics and Example
13. Creating Custom UI Components and Other Custom Objects
14. Configuring JavaServer Faces Applications
16. Uploading Files with Java Servlet Technology
17. Internationalizing and Localizing Web Applications
18. Introduction to Web Services
19. Building Web Services with JAX-WS
20. Building RESTful Web Services with JAX-RS
21. JAX-RS: Advanced Topics and Example
What Is a Message-Driven Bean?
What Makes Message-Driven Beans Different from Session Beans?
When to Use Message-Driven Beans
Using Enterprise Beans in Clients
Deciding on Remote or Local Access
Accessing Local Enterprise Beans Using the No-Interface View
Accessing Local Enterprise Beans That Implement Business Interfaces
The Contents of an Enterprise Bean
Packaging Enterprise Beans in EJB JAR Modules
Packaging Enterprise Beans in WAR Modules
Naming Conventions for Enterprise Beans
The Lifecycles of Enterprise Beans
The Lifecycle of a Stateful Session Bean
The Lifecycle of a Stateless Session Bean
The Lifecycle of a Singleton Session Bean
The Lifecycle of a Message-Driven Bean
Further Information about Enterprise Beans
23. Getting Started with Enterprise Beans
24. Running the Enterprise Bean Examples
25. A Message-Driven Bean Example
26. Using the Embedded Enterprise Bean Container
27. Using Asynchronous Method Invocation in Session Beans
Part V Contexts and Dependency Injection for the Java EE Platform
28. Introduction to Contexts and Dependency Injection for the Java EE Platform
29. Running the Basic Contexts and Dependency Injection Examples
30. Contexts and Dependency Injection for the Java EE Platform: Advanced Topics
31. Running the Advanced Contexts and Dependency Injection Examples
32. Introduction to the Java Persistence API
33. Running the Persistence Examples
34. The Java Persistence Query Language
35. Using the Criteria API to Create Queries
36. Creating and Using String-Based Criteria Queries
37. Controlling Concurrent Access to Entity Data with Locking
38. Using a Second-Level Cache with Java Persistence API Applications
39. Introduction to Security in the Java EE Platform
40. Getting Started Securing Web Applications
41. Getting Started Securing Enterprise Applications
42. Java EE Security: Advanced Topics
Part VIII Java EE Supporting Technologies
43. Introduction to Java EE Supporting Technologies
45. Resources and Resource Adapters
46. The Resource Adapter Example
47. Java Message Service Concepts
48. Java Message Service Examples
49. Bean Validation: Advanced Topics
50. Using Java EE Interceptors
51. Duke's Bookstore Case Study Example
52. Duke's Tutoring Case Study Example
53. Duke's Forest Case Study Example
Written in the Java programming language, an enterprise bean is a server-side component that encapsulates the business logic of an application. The business logic is the code that fulfills the purpose of the application. In an inventory control application, for example, the enterprise beans might implement the business logic in methods called checkInventoryLeveland orderProduct. By invoking these methods, clients can access the inventory services provided by the application.
Benefits of Enterprise Beans
For several reasons, enterprise beans simplify the development of large, distributed applications. First, because the EJB container provides system-level services to enterprise beans, the bean developer can concentrate on solving business problems. The EJB container, rather than the bean developer, is responsible for system-level services, such as transaction management and security authorization.
Second, because the beans rather than the clients contain the application’s business logic, the client developer can focus on the presentation of the client. The client developer does not have to code the routines that implement business rules or access databases. As a result, the clients are thinner, a benefit that is particularly important for clients that run on small devices.
Third, because enterprise beans are portable components, the application assembler can build new applications from existing beans. Provided that they use the standard APIs, these applications can run on any compliant Java EE server.
When to Use Enterprise Beans
You should consider using enterprise beans if your application has any of the following requirements.
- The application must be scalable. To accommodate a growing number of users, you may need to distribute an application’s components across multiple machines. Not only can the enterprise beans of an application run on different machines, but also their location will remain transparent to the clients.
- Transactions must ensure data integrity. Enterprise beans support transactions, the mechanisms that manage the concurrent access of shared objects.
- The application will have a variety of clients. With only a few lines of code, remote clients can easily locate enterprise beans. These clients can be thin, various, and numerous.
Types of Enterprise Beans
Table 22-1 summarizes the two types of enterprise beans. The following sections discuss each type in more detail.
Table 22-1 Enterprise Bean Types
| Enterprise Bean Type | Purpose |
|---|---|
| Session | Performs a task for a client; optionally, may implement a web service |
| Message-driven | Acts as a listener for a particular messaging type, such as the Java Message Service API |
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