INTRODUCTION TO ORACLE WEBLOGIC SERVER

WebLogic is a Java Application Server, a server-side Java program that provides a number of enterprise services for the benefit of the various applications and components running on the server.

These services include the

·          HTTP service

·          Session handling,

·          Distributed naming and lookup,

·          Database access, persistence,

·          Transaction management, caching, concurrency, messaging, security, and much more.

Server-side applications can use these services to implement their application logic, while external clients can either use the published services or directly interact with the applications. Once installed, WebLogic provides various command-line scripts for starting up the server. In fact, many of the WebLogic tools are Java programs that run within a console or as a GUI-based Java application. For this reason, stable releases of WebLogic Server are available on a wide range of platforms, including Windows 2000 Server/Professional, Windows XP, Solaris OS, Red Hat Linux, Tru64, HP-UX, IBM AIX, and other Unix variants.

WebLogic is designed to operate in a distributed environment. This means that you can easily set up an environment where multiple WebLogic instances are running on separate machines within the network, each configured with its own set of applications and services. Alternatively, you may need to design a "cluster" of WebLogic instances distributed across multiple machines over the network, each configured with the same set of applications and services. If you're blessed with powerful, multi-CPU machines, you even may opt to host multiple servers on a single machine. Moreover, WebLogic provides tools that enable you to set up these different scenarios and effectively manage the applications and other resources spread across all the servers. The ease and flexibility with which you can adapt your WebLogic configuration to suit your performance and scalability needs make WebLogic Server a very attractive platform for building real-world enterprise applications.

Features of Weblogic/Weblogic as a J2EE product

The Java 2 Platform, Enterprise Edition (or the J2EE Platform) defines the specifications for an open environment that enables you to build scalable, robust, and secure enterprise Java applications. Any J2EE-compliant application server must provide a number of enterprise services that can then be made available to the applications and components hosted on the server. These services include transaction management, persistence, security, naming and directory services, and more.

In addition, the specification outlines the behavior of various components that reside within an application, such as servlets and EJBs. It lays down the typical life cycle of these server-side components, a standard mechanism for packaging these components, and guidelines for maintaining portability across other compliant application servers. Central to the J2EE specification is the notion of the container-component model. Server-side components run within the context of a container, an abstract entity within the application server that manages the lifetime of the component and provides access to a host of available services. Like a cocoon, a container nurtures and protects the various components deployed to the server. Servlets and JSP pages typically run within a web container, while the EJBs run within an EJB container.

1) Servlets, JSPs, and the web container :

WebLogic Server is equipped with a full-featured servlet engine that complies with the Servlet 2.3 and JSP 1.2 specifications. This means that you can build web applications that contain HTTP servlets and JSP pages for generating dynamic responses to web requests.

2) JDBC and distributed transactions :

Most Java applications use the JDBC API to interact with backend relational databases. Because WebLogic supports the JDBC 2.0 specification, you can configure a ready pool of database connections on WebLogic using any JDBC 2.0-compliant driver. The connection pool provides access to the backend DBMS — you would be hard-pressed to find a DBMS for which a JDBC driver isn't shipped.

The Java Transaction API (JTA) provides the higher-level client access to distributed transactions. Clients need to explicitly initiate distributed transactions when multiple EJBs are needed to fulfill a client request or when the default container-managed transactions are inadequate to implement the business logic. WebLogic extends the capabilities of the JTA by enabling clients to access the current transaction associated with the thread or to obtain a reference to the transaction manager. Moreover, WebLogic allows you to monitor, log, and recover transactions through its transaction recovery service.

3) JNDI and RMI :

Java Naming and Directory Interface (JNDI) provides the standard way for interacting with naming and directory services. J2EE applications use the JNDI API to access various resources that have been configured for the server, including data sources, user transactions, Remote Method Invocation (RMI) objects, EJB home objects, mail sessions, JMS connection factories, JMS topics/queues, and much more. WebLogic's JNDI framework extends over an entire cluster, across all its available members. The cluster-wide JNDI tree manages the JNDI bindings for all clusterable objects. These bindings are automatically replicated across all WebLogic instances in the cluster. Each server maintains a local copy of the global JNDI tree holding replicas of all JNDI bindings in the global JNDI tree. In addition, the local JNDI tree holds bindings for any server-specific resources that must be made available only to the particular WebLogic instance.

4) EJBs

EJBs are reusable server-side Java components that usually encapsulate the business logic of an enterprise application. EJBs typically interact with backend databases and almost always participate in distributed transactions. WebLogic fully supports all the different EJB component types defined in the EJB 2.0 specification: session beans, message-driven beans, and entity beans.

5) JMS

Java Messaging Service (JMS) equips you with a powerful programming model based on asynchronous, decoupled communication. It allows you to build J2EE applications on top of existing message-oriented middleware.

6) JCA

Java Connector Architecture (JCA) provides a standard framework for connecting J2EE application servers to enterprise information systems. Server-side applications and external clients can use the configured resource adapter to interact with the enterprise information system (EIS). Just like JDBC drivers, WebLogic lets you set up a pool of connections to the underlying

Additional Enterprise Features of WebLogic

>WebLogic's security framework

>WebLogic in a clustered environment

>XML support

>Web services

>Management features: (JMX) weblogic uses mbeans to set it properties values

>WebLogic Server Tools: System administration console

>Deployment and development tools (wlst tool, weblogic.deployer, weblogic.admin, ant)