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Extending Java with BEA WebLogic for Linux
Implementing an Enterprise-Quality App Server Under Linux
December 21, 1999
No application server on the market supports Java better than BEA Systems' WebLogic Server. With advanced support for Java Server Pages (JSP), Java Messaging Services, in-memory servlets session-state management, Enterprise JavaBeans (EJB; both session and entity beans), and new clustering technology, BEA Systems' WebLogic application server is a leader in the application server space. It goes above and beyond most of its competitors in terms of Java-oriented features and reliability�particularly in areas of great importance to enterprises.
This emphasis on reliability extends to the entire architecture. While other application servers offer load-balancing, failover and fault tolerance, BEA WebLogic Server 4.5.1 offers these technologies for both Web pages and EJB components. (Most application servers offer these technologies only for Web pages.) While these items may seem obscure on the surface, on a practical level they are vital for mission-critical applications.
As an important example, consider an enterprise that sets up an e-commerce application using a "shopping cart" to process orders and receive credit-card data. When a user gets to the "check out," it is very undesireable for the application server to fail. With WebLogic, transparent replication and failover means that another application server in the cluster is ready to finish the transaction; load balancing means that the WebLogic server will not be overwhelmed�the excess demand will be sent to a less-busy server. BEA uses a load-balancing algorithm to ensure that the load is truly balanced, as opposed to round-robin load-balancing (used by lesser application servers), which merely shuffles requests rather than analyzing where best to send them.
WebLogic Server's EJB clustering�which is not actually part of the server, but rather is an option purchased separately�goes a step further and maintains a transparent connection for stateful EJB objects even when the server goes down. Transactions can be recovered immediately on another server in the cluster. Again, the end result means that an EJB object will never crash and cause pain for the user or the system.
This clustering technology makes WebLogic one of the most scaleable application servers available. When an enterprise's site is a huge success and is processing a large number of transactions (leading to stress on the system), adding more servers and managing them from one centralized position can be done readily, without recoding Java applications.
The Java emphasis, however, does not mean WebLogic is totally immune to the realities of the marketplace, particularly when it comes to supporting Microsoft technologies. WebLogic now supports COM+ objects (moving beyond merely Common Object Request Broker Architecture�CORBA�support), although it does so by wrapping these objects in Java. Similarly, WebLogic supports COM+ bindings for Java and EJB objects. Although the support could be far more transparent, COM and CORBA support is still fairly unique in the application server space.
Obviously, only larger enterprises will have the wherewithal in terms of resources and finances to implement a cluster with a constantly high level of redundancy. Therefore, BEA WebLogic 4.5.1 is best-suited for the enterprise where its $10,000 price tag won't raise eyebrows. However, BEA Systems now ships WebLogic in three different tiers: Server, Enterprise, and Express, with Linux supported only on the Server release. Enterprises will want to match the capabilities of each level to their needs, but even at the lowest level, WebLogic on a Linux platform is still a tool best suited to Fortune 500 company environments.
Also, be warned that WebLogic Server Release 4.5.1 is certified and supported by BEA only on Red Hat Linux using the IBM Linux JVM 1.1.8. (The reason? The IBM JVM uses native threads.) While we didn�t encounter any problems installing and using WebLogic Server on a Slackware Linux 7 system, we wouldn't recommend going against the BEA guidelines for a production-grade installation.