Web hosting india - 38 Chapter 2 instances of your bean class.
38 Chapter 2 instances of your bean class. This saves you from having to worry about networking issues (the container provides networking as a service to you). Thus EJB products automatically convert your standalone, networkless components into distributed, network-aware entities. Implicit support. EJB containers automatically handle concurrent requests from clients. EJB containers provide built-in thread support, instantiating multiple copies of your component as necessary by instantiating lots of instances of your enterprise bean and pushing one thread through each instance. If multiple clients simultaneously invoke methods on a bean, the invocations are serialized, or performed lock step. The container will allow only one client to call a bean at a time. The other clients are routed to other bean instances of the same class or are forced to wait. (Behind the scenes, the container might use Java thread synchronization to aid with this. The actual algorithm used is container- specific.) The value of threading is obvious who enjoys writing multithreaded code? Implicit component location transparency. Clients of components are decoupled from the specific whereabouts of the component being used. Implicit monitoring. The EJB container can track which methods are invoked, display a real-time usage graph on a system administrator s user interface, gather data for intelligent load balancing, and more. An EJB container is not required to perform these tasks; however, high-end EJB containers perform these tasks at the point of interception. Thus, the EJB container acts as a layer of indirection between the client code and the bean. This layer of indirection manifests itself as a single network- aware object called the EJB object. The EJB object is the request interceptor we alluded to earlier. As the old saying goes, a layer of indirection solves every problem in computer science. The EJB object is a surrogate object that knows about networking, transactions, security, and more. It is an intelligent object that knows how to perform intermediate logic that the EJB container requires before a method call is serviced by a bean class instance. An EJB object is the request interceptor, or the glue, between the client and the bean. EJB objects replicate and expose every business method that the bean itself exposes. EJB objects delegate all client requests to beans. Figure 2.5 depicts EJB objects. You should think of EJB objects as physical parts of the container; all EJB objects have container-specific code inside of them. (Each container handles middleware differently and provides different qualities of service.) Because each bean s EJB object is different, your container vendor generates the class file for your EJB objects automatically.
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