Enterprise JavaBeans Architecture

EJB 3.0 uses lifecycle callback annotations like @PrePassivate to handle passivation events. The annotated method is automatically invoked when the container passivates the bean. This eliminates the need to implement callback interfaces or use deployment descriptors.

Enterprise JavaBeans (EJBs) differ from regular JavaBeans in three key ways: EJBs are managed by an EJB container that handles lifecycle, security, and transactions; they execute on the server side in application servers; and they can participate in distributed transactions. Regular JavaBeans are simple reusable components that run client-side without container management.

When a request arrives for an EJB method, the container performs several preprocessing tasks before invoking the bean: it can start a transaction context if the method requires one, and it checks security credentials to verify the client's authorization. The container does not simply pass requests directly - it provides these middleware services first.

Stateful session beans maintain conversational state with a specific client. The correct answer is D because stateful session beans can receive initial state information through arguments in their create methods. Option A is incorrect because while there's a relationship, it's not accurately described as many-to-one. Option B is false because bean instances have a finite lifecycle. Option C is incorrect because the container doesn't arbitrarily discard stateful beans - passivation/activation follows specific rules. Option E is false because instances are created on client demand, not deployment.

Entity beans represent persistent business data. Option D is correct because entity beans represent persistent data with unique primary key identification. Option A is incorrect because multiple clients can access the same entity bean instance. Option B is false because containers can discard/passivate entity beans to manage resources. Option C is misleading because while instances have identity within the container, the question's phrasing is imprecise. Entity beans fundamentally exist to represent data in persistent storage.

Entity beans represent data in persistent storage that can be accessed by multiple clients concurrently. The answer is False because entity beans do NOT have a one-to-one relationship with clients. Multiple clients can access the same entity bean instance (representing the same underlying data) simultaneously. Entity beans are designed for shared access to persistent data, unlike stateful session beans which maintain exclusive conversational state with one client.

In EJB, a bean's remote interface can extend other remote interfaces using Java's extends clause. This is True because remote interfaces are standard Java interfaces that follow normal inheritance rules. A bean's remote interface can extend from other remote interfaces (or regular interfaces), allowing interface hierarchies and code reuse. The bean implementation class then implements this extended interface, inheriting all method signatures.

In RMI (Remote Method Invocation), each remote object instance has a unique stub and skeleton generated specifically for it. The stub acts as the client-side proxy, while the skeleton is the server-side dispatcher. This one-to-one relationship ensures proper routing of remote method calls. The answer is True because stub and skeleton pairs are generated during the build process and are uniquely associated with their specific remote object interface.

Entity bean primary keys must be serializable and comparable to support caching and database operations. The answer is False because Java primitive types (int, long, etc.) are not objects and cannot be used directly. Instead, you must use wrapper classes (Integer, Long, String) or custom primary key classes that implement Serializable. The container needs to handle primary keys as objects for operations like findByPrimaryKey.

EJB callback methods like ejbCreate and ejbRemove have standardized signatures in the EJB specification, but their internal implementation varies by application server vendor. The answer is True because while the API contract is the same (method names, signatures, and behavior requirements), each vendor (WebLogic, JBoss, WebSphere, etc.) implements these differently internally. The container manages the bean lifecycle, and vendor implementations optimize this differently.

Message Driven Beans (MDBs) share structural similarities with Session Beans. The answer is True because MDBs follow the same lifecycle callback pattern (ejbCreate, ejbRemove) as session beans, and they're also managed by the container. The key difference is MDBs don't have a client-visible interface - they respond to JMS messages instead of direct client calls. But structurally, they mimic session bean patterns for lifecycle management.

The OWB Repository is the central storage component that holds all metadata definitions for the data warehouse, including source and target definitions, transformations (150+ presets), mappings, and process flows. The Repository acts as the single source of truth for all OWB metadata. Other options are client tools or runtime components, not storage.

The OWB Client is the primary design interface used to create and configure data warehouse objects, ETL processes, mappings, and process flows. It includes various editors, bridges for connecting to external systems, and integrators, and serves as the main access point to other OWB components. The Repository stores metadata, Runtime tools manage execution.

The OWB Design Browser Client is a web-based interface for viewing metadata objects, generating reports, and performing lineage analysis (tracing data flow) and impact analysis (determining effects of changes). It provides read-only access to the metadata repository. The OWB Client is for design, Repository is storage, Runtime tools are for execution.

The OWB Runtime Audit Browser is specifically designed to run reports on audit trails and error information captured during ETL job execution. It helps diagnose issues by showing what failed, why, and when. The Repository stores metadata, Client is for design, Assistant is for setup, and Design Browser is for metadata viewing.

The OWB Runtime Assistant is used for administrative tasks including configuring the runtime repository, setting up target schemas in the database, and maintaining deployment information along with runtime audit/error logs. It bridges the gap between design and execution. The Repository stores metadata, Client designs, and other tools don't handle this setup.

OWB architecture has two main components: the OWB Client (design-time) and the OWB Repository (storage/metadata). While the Repository can be considered a server component, the fundamental architecture is a 2-component client-server model. Options suggesting 1, 3, 4, or 5 components don't match the actual architecture.

The Module Editor in OWB is used to define and configure modules, which are logical containers for source and target data warehouse objects. Modules organize related objects (tables, dimensions, etc.) and act as collections for DW objects. Code Editors are for scripts, Mapping Editors for ETL flows, Text Editors for text, Object Editors isn't a standard OWB term.

The Object Editor in Oracle Warehouse Builder (OWB) is the main editor that provides access to specialized editors for different object types. It includes the table editor, dimension editor, fact editor, and other property editors that allow you to modify the characteristics and structure of various warehouse objects. The Client Editor and Text Editor are not OWB components, while Dimension Editor and Fact Editor are sub-editors within the Object Editor, not standalone editors.

The Mapping Editor in OWB is specifically designed for creating ETL (Extract, Transform, Load) mappings that define how data flows from source systems to the target data warehouse. It provides a graphical interface to visualize relationships between source and target objects, includes transformation operators (key lookup, sequence generation, etc.), supports custom transformations, enables validation of mappings, and generates the deployment code. The Object Editor is for object properties, Code Editor for generated code modification, and Transformation Editor is not a standard OWB component.