Java Queries

Explain the Front Controller design pattern or explain J2EE design patterns?

A J2EE system requires a centralized access point for HTTP request handling to support the integration of system services like security, data validation etc, content retrieval, view management, and dispatching.

Explain declarative security for WEB applications?

Servlet containers implement declarative security. The administration is done through the deployment descriptor web.xml file.

What is a filter, and how does it work?

A filter dynamically intercepts requests and responses to transform or use the information contained in the requests or responses but typically do not themselves create responses. Filters can also be used to transform the response from the Servlet or JSP before sending it back to client.

What are the benefits of Clustering and workload management?

1. It balances client processing requests, allowing incoming work requests to be distributed according to a configured Workload Management selection policy.

What is the difference between Message Driven Beans and Stateless Session beans?

In several ways, the dynamic creation and allocation of message-driven bean instances mimics the behavior of stateless session EJB instances, which exist only for the duration of a particular method call.

What are the basic classes required in the client for invoking an EJB?

The home and the remote interfaces, the implementation of the Naming Context Factory, the stubs and skeletons. In some App servers the stubs and the skeletons can be dynamically downloaded from the server

What is the new basic requirement for a CMP entity bean class in 2.0 from that of ejb 1.1?

must be abstract class. The container extends it and implements methods which are required for managing the relationships

How does a container-managed relationship work?

An entity bean accesses related entity beans by means of the accessor methods for its container-managed relationship fields, which are specified by the cmr-field elements of its abstract persistence schema defined in the deployment descriptor.

What does a remove method do for different cases of beans?

Stateless Session : Does not do anything to the bean as moving the bean from free pool to cache are managed by the container depending on load. Stateful Session: Removes the bean from the cache. Entity Bean: Deletes the bean (data) from persistent storage

What is the relationship between local interfaces and container-managed relationships?

Entity beans that have container-managed relationships with other entity beans, must be accessed in the same local scope as those related beans, and therefore typically provide a local client view.