26th October, 2018
At the end of this module you will be able to:
A distributed system consists of multiple autonomous computers that communicate through a computer network. The computers interact with each other in order to achieve a common goal. A computer program that runs in a distributed system is called a distributed program.
To be truly reliable, a distributed system must have the following characteristics:
How Standards Help:
The J2EE Standard:
The J2EE Architecture
Containers are the interface between a component and the low-level platform-specific functionality that supports the component. Before a Web, enterprise bean, or application client component can be executed, it must be assembled into a J2EE application and deployed into its container.
The assembly process involves specifying container settings for each component in the J2EE application and for the J2EE application itself. Container settings customize the underlying support provided by the J2EE server, which includes services such as security, transaction management, Java Naming and Directory Interface (JNDI) lookups, and remote connectivity. Here are some of the highlights:
The J2EE security model lets you configure a Web component or enterprise bean, so that system resources are accessed only by authorized users.
The J2EE transaction model lets you specify relationships among methods that make up a single transaction so that all methods in one transaction are treated as a single unit.
JNDI lookup services provide a unified interface to multiple naming and directory services in the enterprise so that application components can access naming and directory services.
The fact that the J2EE architecture provides configurable services means that application components within the same J2EE application can behave differently based on where they are deployed. For example, an enterprise bean can have security settings that allow it a certain level of access to database data in one production environment and another level of database access in another production environment.
J2EE Container Types
The deployment process installs J2EE application components in the J2EE containers….
The runtime portion of a J2EE product. A J2EE server provides EJB and Web containers.
Enterprise JavaBeans (EJB) container
Manages the execution of enterprise beans for J2EE applications. Enterprise beans and their container run on the J2EE server.
Manages the execution of JSP page and servlets components for J2EE applications. Web components and their container run on the J2EE server.
Application client container
Manages the execution of application client components. Application clients and their container run on the client.
Manages the execution of applets. Consists of a Web browser and Java Plug-in running on the client together.
JavaServer Pages (JSPs)
Enterprise JavaBeans (EJBs)
JDBC (Java Database Connectivity)
Java Naming & Directory Interface (JNDI)
Java Transaction API (JTA):
Java Message Service (JMS)
Java Authentication and Authorization
The specification describes MBeans, which are the building blocks of JMX
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