Programming WebLogic RMI
Using RMI over IIOP
The following sections provide a high-level view of RMI over IIOP:
What is RMI over IIOP?
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.
Overview of WebLogic RMI-IIOP
WebLogic Server provides its own ORB implementation which is instantiated by default when programs call ORB.init(), or when "java:comp/ORB" is looked up in JNDI. See CORBA Support for WebLogic Server for information how WebLogic Server complies with specifications for CORBA support in J2SE 1.4.
The WebLogic Server implementation of RMI-IIOP allows you to:
- Connect Java RMI clients to WebLogic Server using the standardized IIOP protocol
- Connect CORBA/IDL clients, including those written in C++, to WebLogic Server
- Interoperate between WebLogic Server and Tuxedo clients
- Connect a variety of clients to EJBs hosted on WebLogic Server
How you develop your RMI-IIOP applications depends on what services and clients you are trying to integrate. See Programming Stand-alone Clients for more information on how to create applications for various clients types that use RMI and RMI-IIOP.
Figure 7-1 shows RMI Object Relationships for objects that use IIOP. Figure 7-1 RMI Object Relationships
Support for RMI-IIOP with RMI (Java) Clients
You can use RMI-IIOP with Java/RMI clients, taking advantage of the standard IIOP protocol. WebLogic Server provides multiple options for using RMI-IIOP in a Java-to-Java environment, including the new Java EE Application Client (thin client), which is based on the new small footprint client jar. To use the new thin client, you need to have the wlclient.jar (located in WL_HOME/server/lib) on the client side's CLASSPATH. For more information on RMI-IIOP client options, see Programming Stand-alone Clients.
Support for RMI-IIOP with Tuxedo Client
WebLogic Server 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 Programmer's Guide.
Support for RMI-IIOP with CORBA/IDL Clients
The developer community requires the ability to access Java EE 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.
Protocol Compatibility
Interoperability between this release and prior WebLogic Server releases is supported in the following scenarios:
Server-to-Server Interoperability
The following table identifies supported options for achieving interoperability between two WebLogic Server instances.
| To Server From Server | WebLogic Server 8.1 | WebLogic Server 9.x | WebLogic Server 10.0 |
|---|---|---|---|
| WebLogic Server 8.1 | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services |
| WebLogic Server 9.x | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services |
| WebLogic Server 10.0 | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services |
| Sun JDK ORB client1 | RMI/IIOP2 | RMI/IIOP3 | RMI/IIOP4 |
| 1This option involves calling directly into the JDK ORB from within application hosted on WebLogic Server. 2 JDK 1.3.x or 1.4.1. No clustering. No transaction propagation 3 JDK 5.0. No clustering. No transaction propagation 4 JDK 5.0. No clustering. No transaction propagation |
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.
| To Server From Client (stand-alone) | WebLogic Server 8.1 | WebLogic Server 9.x | WebLogic Server 10.0 |
|---|---|---|---|
| WebLogic Server 8.1 | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services |
| WebLogic Server 9.x | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services |
| WebLogic Server 10.0 | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services | RMI/T3 RMI/IIOP HTTP Web Services |
| Sun JDK ORB client1 | RMI/IIOP2 | RMI/IIOP3 | RMI/IIOP4 |
| 1 This option involved calling directly into the JDK ORB from within a client application. 2 JDK 1.3.x or 1.4.1. No clustering. No transaction propagation 3 JDK 5.0. No clustering. No transaction propagation 4 JDK 5.0. No clustering. No transaction propagation |