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What are Session Beans?
Session Beans are an essential component in Enterprise JavaBeans (EJB) technology, which is a server-side component model for developing distributed applications in Java. Session Beans provide a way to encapsulate business logic and are responsible for executing specific tasks or services for the clients.
Session Beans have stateful and stateless types.
Stateful Session Beans
Stateful Session Beans maintain conversational state information with a specific client throughout multiple method invocations. They are created and associated with the client for the duration of a session and can store client-specific data. These beans are useful when state persistence is required or when business processes involve multiple steps.
An example of a stateful session bean can be seen in an e-commerce application. In the shopping cart, the stateful session bean would track the items added by a specific user, manage the order process, and handle the payment procedures.
Stateless Session Beans
Stateless Session Beans do not maintain any specific client state between method invocations. Each method invocation is independent and doesn’t affect other invocations. They are shared by multiple clients and are typically used for operations that don’t require storing client-specific data.
An example of a stateless session bean can be found in a banking system. The session bean provides methods for transferring funds, calculating interest, or verifying account details. These operations do not require maintaining any state between invocations.
Explain the Basic Concept of EJB
The basic concept of Enterprise JavaBeans (EJB) is to provide a standardized way of developing scalable, robust, and secure enterprise applications. EJB technology consists of a set of specifications that define how the server-side components of an application should be developed and deployed.
EJB is built on top of the Java Platform, Enterprise Edition (Java EE), and provides a component model that allows developers to focus on business logic rather than low-level technical details. It promotes the principles of component-based development, such as modularity, reusability, and integration.
The key concepts of EJB include:
1. Components: EJB components are the building blocks of an application. They encapsulate business logic and can be invoked by the clients. Session Beans, Entity Beans, and Message-Driven Beans are the three main types of EJB components.
2. Container: EJB components are executed within a container, which provides services such as transaction management, security, concurrency, and resource pooling. The container handles the lifecycle of the components and ensures that they comply with the EJB specifications.
3. Remote Method Invocation: EJB components can be accessed remotely by clients, allowing distributed applications to call methods on the server-side components. This enables the development of systems that are scalable, flexible, and can be deployed across multiple machines.
4. Declarative Services: EJB relies on declarative programming to configure various aspects of the application, such as security, transaction management, and lifecycle management. Developers can specify these requirements using deployment descriptors or annotations, reducing the amount of boilerplate code.
In summary, EJB provides a powerful framework for developing enterprise applications by encapsulating business logic into modular components that can be easily distributed, managed, and scaled. It simplifies the development process and promotes the principles of building robust and scalable systems.
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