Java 2EE and XML Development

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   Both your application and the remote system must support the same remote object architecture, directly or through a bridging tool like Intrin-syc Software’s JIntegra product. For many legacy systems, this type of integration is not possible due to lack of support for distributed objects.


■    Using an intermediary lookup service remotely takes time and can degrade overall system performance if references to remote objects cannot be effectively cached and reused.


EJB supports object level integration extensively via RMI. In fact, this integration model is the basis of all interactions between EJBs and their clients, both remote


Local Object


Server Stub


Communication


Client Skeleton


Remote Object (Server)


(Client)


(proxy)


1 * *


(proxy)

Figure 4.6 Remote object interaction using proxies


and local. Since RMI can be done over IIOP, EJB components can participate in CORBA systems. Additionally, products such as JIntegra can be used to access EJB from DCOM systems. Consider using the Session Fagade or Aggregate Entity pattern to encapsulate the integration points between your internal components and remote systems.

Constraint-based modeling


Now that we have identified our system integration options, we need a method for choosing which to use in a given situation. An effective approach is to begin your analysis without assumptions and narrow your options by considering the limitations and capabilities of the systems to which you must connect. This is known as constraint-based modeling, in which the existing environment guides much of the integration architecture.

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