J2EE Overview

J2EE Overview

Overview

J2EE apps are assemblages of Java programs that are packaged with miscellaneous configuration files, organized in directories according to agreed upon specs, and deployed to servers, where they are controlled by daemons.
The J2EE server daemon is a container for every J2EE component type, and can be customized to include security services, transaction management, JNDI lookups, and remote connectivity. Other, nonconfigurarable services, include life cycle management, resource pooling, and data persistence.
J2EE apps are packaged with XML-based deployment descriptors runtime configration information, which is read by the J2EE server daemon.
J2EE applications are assembled into Enterprise Archive (EAR) files, which are standard Java Archive (JAR) files with an .ear extension.

Software

J2EE SDK Package that comes with the J2EE application server. Used to test whether an app complies with the J2EE specification.

J2SE SDK Package that provides APIs for writing J2EE components. Also used to run the J2EE SDK.

deploytool Utility for assembling, verifying, and deploying J2EE applications.

j2ee Script for starting and stopping the J2EE server daemon.

cloudscape Script for starting and stopping the default database

j2eeadmin Script for adding JDBC drivers, JMS destinations, and connection factories for various resources

keytool Script for creating public and private keys and generate X509 self-signed certificate

realmtool Script for importing certificate files, add J2EE users to and remove J2EE users from the authentication and authorization list for a J2EE application

packager Script for packaging J2EE application components into EAR, EJB JAR, application client JAR, and WAR files

verifier Script for verifying that EAR, EJB JAR, application client JAR, and WAR files are well-formed and comply with the J2EE specification

runclient Script for running a J2EE application client

cleanup Script for removing deployed applications from the J2EE server daemon

Enterprise Java Beans

Enterprise JavaBeans (EJBs) are server-side components that support transactions, which is the concurrent access of shared objects.
Types of EJBs include:

Session Performs a task for a client

Entity Business object existing in persistent storage

Message-Driven Listener for JMS, processing messages asynchronously

J2EE SDK	Package that comes with the J2EE application server. Used to test whether an app complies with the J2EE specification.
J2SE SDK	Package that provides APIs for writing J2EE components. Also used to run the J2EE SDK.
deploytool	Utility for assembling, verifying, and deploying J2EE applications.
j2ee	Script for starting and stopping the J2EE server daemon.
cloudscape	Script for starting and stopping the default database
j2eeadmin	Script for adding JDBC drivers, JMS destinations, and connection factories for various resources
keytool	Script for creating public and private keys and generate X509 self-signed certificate
realmtool	Script for importing certificate files, add J2EE users to and remove J2EE users from the authentication and authorization list for a J2EE application
packager	Script for packaging J2EE application components into EAR, EJB JAR, application client JAR, and WAR files
verifier	Script for verifying that EAR, EJB JAR, application client JAR, and WAR files are well-formed and comply with the J2EE specification
runclient	Script for running a J2EE application client
cleanup	Script for removing deployed applications from the J2EE server daemon

Session	Performs a task for a client
Entity	Business object existing in persistent storage
Message-Driven	Listener for JMS, processing messages asynchronously