This course offers the Java programmer a grounding in the Enterprise JavaBeans (EJB) architecture and the skills to develop EJBs effectively for enterprise development efforts. EJB’s position at the heart of the Java Enterprise platform and the use of EJB application servers as the backbone of large-scale distributed systems are studied. We consider the advantages of the application server architecture – transaction control, security, persistence, scalability through pooling and clustering – and study the development process for entity and session beans in depth. The J2EE reference implementation is used for all demo and lab work, and we emphasize portable EJB 2.1 code.

The focus for the first module is on end-to-end connectivity. The module follows a path roughly from the data layer to the presentation layer, so we look at entity beans first, and work demos and exercises in both Bean-Managed and Container-Managed Persistent Beans. Then the EJB session layer is considered, and both stateless and stateful session beans are developed. As part of the lab work, these are hooked to provided JSPs to illustrate the complete system and typical architecture.

Students then proceed to the second module, which begins with some 2.x-specific features, such as message-driven beans and the features of 2.x container-managed persistence. Two EJB applications are connected via JMS messaging, one sending messages with raw JMS code, and one using a message-driven bean to receive and handle those messages by updating an accounting database. Design implications of CMP are discussed, as are the new capabilities for EJB design: home and select methods.

Students then move on to study declarative and programmatic transaction control. The EJB security architecture is also considered, and a simple role-based authorization design applied to the course’s main lab project. A short chapter on exception handling in EJB clarifies the standards for exception propagation and transaction control.

The next chapter introduces the new features in EJB 2.1 for implementing SOAP-based Web services, using the JAX-RPC mappings between Java and WSDL. Also new for 2.1, there is a short chapter on using the EJB timer service. The course concludes with a chapter on best-practice EJB development: optimizations, design patterns and implementation techniques.

During this course, students will:

• Understand the role of Enterprise JavaBeans in enterprise-level systems development, and its relationship to other J2EE technologies such as JSP, servlets, JMS, CORBA, and XML.
• Understand the EJB architecture: the role of the EJB container in mediating contact between the client and the bean, transaction control, authorization control, and the importance of object pooling.
• Understand the development cycle for EJBs: Java source code and compilation, XML deployment descriptors, EJB compilation and deployment, and use by an application server.
• Understand the role of entity beans, their lifecycle and interactions with the container.
• Develop and test BMP and CMP entity beans and understand the importance of each of the entity-bean methods in assisting the container in pooling.
• Understand the role of session beans, their lifecycle and interactions with the container.
• Develop and test stateless and stateful session beans and effectively manage passivation/activation cycles.
• Use the bean context interfaces to assist with persistence code and to correctly establish bean-to-bean communication.
• Develop message-driven beans and understand their unique nature within the EJB architecture.
• Use 2.x container-managed persistence and make intelligent design choices based on the practical implications of BMP and CMP features.
• Implement 2.x CMP entity bean relationships.
• Understand the EJB transaction architecture and apply transaction attributes to EJB systems, using both declarative and programmatic approaches.
• Understand the EJB security architecture and apply roles and authorization attributes to EJB systems – again, using both declarative and programmatic techniques.
• Implement SOAP-based Web services using stateless session beans and JAX-RPC, and understand the relationship between JAXM and message-driven beans.
• Create and respond to EJB timers in bean code.
• Tune EJB application servers and EJB code for performance.
• Understand and apply design patterns that are important to common distributed systems and EJB systems in particular.

Module 1: Introduction to Enterprise JavaBeans

1. The EJB Architecture

EJB and the Java Enterprise Platform
EJB and CORBA
EJB Costs and Benefits
What is an EJB?
Entity, Session, and Message-Driven Beans
EJB Roles
The EJB Container
The Home and EJB Objects
EJB Development
Remote Interface
Home Interface
Bean Class
Remote, Local, and Web-Service Component Interfaces
Multiple Maintenance Points
Using JNDI in EJB

2. Entity Beans: Bean-Managed Persistence

Persistence Mechanism
Instance versus Incarnation – Similarities to the CORBA PSS
EntityBean Interface and Responsibilities
Entity Bean Interactions, Lifecycle and State Transitions
Primary Keys
EntityContext Interface and Discovering the Primary Key
Creation and Removal
Load and Store
Finder Methods
Eager vs. Lazy Persistence

3. Entity Beans: Container-Managed Persistence

Two Contracts for Persistence
Declaring a Data Source
Declaring Persistent Fields
Implementing Finder Methods
What the Container Does
Architecture
2.0 Architecture
CMP Limitations

4. Stateless Session Beans

Session Beans and the Presentation Layer
Stateful vs. Stateless Sessions
Stateful Session Bean Interactions, Lifecycle and State Transitions
Stateless Session Bean Interactions, Lifecycle and State Transitions
Finding Entity Beans
Passing Value Objects

5. Stateful Session Beans

Stateful Session Beans
Object Pooling and Passivation/Activation
Activation and Passivation
Choosing Between Stateful and Stateless

Module 2: Effective Enterprise JavaBeans

1. Message-Driven Beans

Asynchronous Messaging
The Java Message Service
Message-Driven Beans
Lifecycle of a Message-Driven Bean
Implementing Message-Driven Beans
Messages and Transactions
Message-Driven Beans and Transactions

2. Persistence

BMP and CMP
Container-Managed Relationships
EJB Query Language
Declaring Finder Methods
Declaring Select Methods
Calling ejbSelect Methods from Bean Code
Home Methods
Design Considerations

3. Security

The Need for Security
Authentication
Authorization Model
Declarative Authorization and Roles
Abstract Roles and Application Assembly
Actual Roles and Deployment
Programmatic Authorization
Identifying the Caller

4. Transactions

The Need for Transactions
ACID Properties
Declarative Transactions
Transaction Attributes and Isolation Levels
Scenarios
Programmatic Transactions
EJB Context and Monitoring the Transaction
SessionSynchronization Interface

5. Web Services and EJB

SOAP-Based Web Services
WSDL
JAX-RPC
EJB 2.1 and JAX-RPC
Session Beans as Web Service Endpoints
How It Works – Build Time and Runtime
The Bean’s Service Endpoint Interface
SOAP as an RMI Transport
Adding a SOAP Interface to a Session Bean
Generating From WSDL
“ Gotchas”
J2EE and Web Services

6. Exception Handling

Java Exceptions
Remote Exceptions
EJB Exceptions
Application Exceptions
Propagation to the Client
System Exceptions
Automatic Transaction Rollback

7. The Timer Service

Uses for Timers
The EJB Timer Service
Service, TimedObject and Timer Interfaces
Timer Handles
Creating a Timer
Implementing ejbTimeout
Timers and Transactions

8. Best Practices

The Bean Environment
Expressing UML Designs for EJB
Creation and Finder Semantics
Designing for Latency
Value Object Pattern
Local vs. Remote Beans and the Façade Pattern
Transaction Models
When Not to Use EJB
Flyweight Pattern versus EJB Pooling
Entity Bean Performance Optimizations