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| e-docs > WebLogic Server > Programming WebLogic RMI over IIOP > Overview of RMI over IIOP |
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Programming WebLogic RMI over IIOP
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The following sections provide a high-level view of RMI over IIOP:
What Are RMI and RMI over IIOP?
To understand RMI-IIOP, you should first have a working knowledge of RMI. Remote Method Invocation (RMI) is the standard for distributed object computing in Java. RMI enables an application to obtain a reference to an object that exists elsewhere in the network, and then invoke methods on that object as though it existed locally in the client's virtual machine. RMI specifies how distributed Java applications should operate over multiple Java virtual machines. RMI is written in Java and is designed exclusively for Java programs.
RMI over IIOP extends RMI to work across the IIOP protocol. This has two benefits that you can leverage. In a Java to Java paradigm this allows you to program against the standardized Internet Interop-Orb-Protocol (IIOP). If you are not working in a Java-only environment, it allows your Java programs to interact with Common Object Request Broker Architecture (CORBA) clients and execute CORBA objects. CORBA clients can be written in a variety of languages (including C++) and use the Interface-Definition-Language (IDL) to interact with a remote object.
RMI over IIOP is based on the RMI programming model and, to a lesser extent, the Java Naming and Directory Interface (JNDI). For detailed information on WebLogic RMI and JNDI, refer to Using WebLogic RMI and Programming with WebLogic JNDI. Both technologies are crucial to RMI-IIOP and it is highly recommended that you become familiar with their general concepts before starting to build an RMI-IIOP application.
The WebLogic Server 7.0 implementation of RMI-IIOP allows you to:
This document describes how to create applications for various clients types that use RMI and RMI-IIOP. How you develop your RMI-IIOP applications depends on what services and clients you are trying to integrate.
The following figure shows an RMI Object Relationships that uses IIOP
Support for RMI-IIOP with RMI (Java) Clients
You can use RMI-IIOP with Java/RMI clients, taking advantage of the standard IIOP protocol. The release of the 1.3.1 JDK facilitates this capability, and WebLogic Server 7.0 can readily be used with RMI-IIOP in a Java-to-Java environment. There is also a new "fat" RMI-IIOP RMI Client that can be used to develop fully clusterable RMI-IIOP applications. To use this new WebLogic RMI-IIOP RMI Client, you need to have the weblogic.jar (located in WL_HOME/server/lib) on the client side's CLASSPATH, and use the -Dweblogic.system.iiop.enableClient=true command line option when starting the client.
Support for RMI-IIOP with Tuxedo Clients
WebLogic Server 7.0 contains an implementation of the WebLogic Tuxedo Connector, an underlying technology that enables you to interoperate with Tuxedo servers. Using WebLogic Tuxedo Connector, you can leverage Tuxedo as an ORB, or integrate legacy Tuxedo systems with applications you have developed on WebLogic Server. For more information, see the WebLogic Tuxedo Connector Guide.
Support for RMI-IIOP with CORBA/IDL Clients
The developer community requires the ability to access J2EE services from CORBA/IDL clients. However, Java and CORBA are based on very different object models. Because of this, sharing data between objects created in the two programming paradigms was, until recently, limited to Remote and CORBA primitive data types. Neither CORBA structures nor Java objects could be readily passed between disparate objects. To address this limitation, the Object Management Group (OMG) created the Objects-by-Value specification . This specification defines the enabling technology for exporting the Java object model into the CORBA/IDL programming model--allowing for the interchange of complex data types between the two models. WebLogic Server can support Objects-by-Value with any CORBA ORB that correctly implements the specification.
Interoperability between WebLogic Server 7.0 and WebLogic Server 6.x and 8.1 is supported in the following scenarios:
Server-to-Server Interoperability
The following table identifies supported options for achieving interoperability between two WebLogic Server instances.
Table 1-1 WebLogic Server-to-Server Interoperability
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WebLogic Server 6.1 SP2 and any service pack higher than SP2 |
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Web Services1 |
Web Services2 |
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WebLogic Server 6.1 SP2 and any service pack higher than SP2 |
RMI/IIOP3 |
RMI/IIOP4 |
RMI/T35 RMI/IIOP6 Web Services7 |
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RMI/IIOP8 |
RMI/IIOP9 |
RMI/IIOP10 Web Services11 |
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RMI/IIOP12 |
RMI/IIOP13 Web Services14 |
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Sun JDK ORB client15 |
RMI/IIOP16 |
RMI/IIOP17 |
RMI/IIOP18 |
RMI/IIOP19 |
Client-to-Server Interoperability
The following table identifies supported options for achieving interoperability between a stand-alone Java client application and a WebLogic Server instance.
Table 1-2 Client-to-Server Interoperability
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Web Services1 |
Web Services2 |
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Web Services3 |
RMI/T34 Web Services5 |
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RMI/IIOP6 |
RMI/IIOP7 |
RMI/IIOP8 Web Services9 |
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RMI/IIOP10 |
RMI/IIOP11 Web Services12 |
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Sun JDK ORB client13 |
RMI/IIOP14 |
RMI/IIOP15 |
RMI/IIOP16 |
RMI/IIOP17 |
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