JavaTM RMI over IIOP
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JavaTM Remote Method Invocation over Internet Inter-ORB Protocol technology ("RMI-IIOP") is part of the
JavaTM 2 Platform, Standard Edition (J2SETM). The RMI Programming
Model enables the programming of CORBA servers and applications via the rmi API.
You can choose to work completely within the Java programming language using the Java Remote
Method Protocol (JRMP) as the transport, or work with other CORBA-compliant programming
languages using the Internet InterORB Protocol (IIOP).
RMI-IIOP utilizes the Java CORBA Object Request
Broker (ORB) and IIOP, so you can write all of your code in the Java programming
language, and use the rmic
compiler to generate the code necessary for connecting your applications via the Internet
InterORB Protocol (IIOP) to others
written in any CORBA-compliant language. To work with CORBA applications
in other languages, IDL can be generated from Java programming language
interfaces using the rmic compiler with the -idl
option. To generate IIOP stubs and tie classes, use the rmic
compiler with the -iiop option. For more information
on using rmic, link to rmic - The Java RMI Compiler.
When should I use RMI-IIOP?
RMI-IIOP is for developers who program in the
Java programming language and want to program to the RMI interfaces, but use IIOP as the
underlying transport. RMI-IIOP provides interoperability with other CORBA
objects implemented in various languages - but only if all the remote interfaces
are originally defined as Java RMI interfaces. It is of particular interest to
programmers using Enterprise JavaBeansTM (EJBTM), since the remote object model for
EJB components is based on the RMI API.
RMI-IIOP combines the best features of Java Remote
Method Invocation (RMI) with the best features of CORBA. RMI-IIOP speeds distributed
application development by
allowing developers to work completely in the Java programming
language, writing remote
interfaces in the Java programming language and implementing them simply
using Java technology and the Java RMI APIs.
When using RMI-IIOP to
produce technology-based distributed applications written in the Java programming language, there is no
separate Interface Definition Language (IDL) or mapping to learn: the remote interfaces can
be implemented in any other language that is supported by an OMG mapping and a vendor
for that language. Similarly, clients can be written in other languages
using IDL derived from the remote Java technology-based interfaces.
RMI-IIOP provides flexibility by allowing developers to
pass any Java object between application
components either by reference or by value.
Like CORBA, RMI-IIOP is based on open
standards defined with the participation of hundreds of vendors and
users in the Object Management Group. Like CORBA, RMI-IIOP uses Internet Inter-ORB Protocol
(IIOP) as its communication protocol. IIOP eases legacy application and platform
integration by allowing application components written in C++, Smalltalk, and other CORBA
supported languages to communicate with components running on the Java platform.
What other options do I have for distributed application development?
Developers who program using the JavaTM programming language can choose several
solutions for creating distributed applications programs.
JavaTMRMI technology - If all of your
applications are written in the Java programming language, you will probably want
to use Java RMI technology to enable communication between Java
objects on different virtual machines and different
physical machines. Using Java RMI technology without its IIOP option leverages its strengths of
security, and garbage collection.
JavaTM IDL technology - Java IDL technology are for CORBA programmers who want to program in the
language based on interfaces defined in CORBA Interface Definition Language
(IDL). This is "business as usual" CORBA programming, supporting the
Java platform in exactly
the same way as other languages like C++ or COBOL.
(EJBTM) technology is part of the
Java 2 Platform, Enterprise Edition. EJB components use the Java RMI/Java IDL technology for their
distributed object model, and use the Java Transaction Service (JTS) for their distributed
transaction model. When Enterprise JavaBeans components are implemented using the RMI-IIOP protocol
for EJB component interoperability in heterogeneous server environments, the standard mapping of the
EJB architecture to CORBA enables interoperability with multivendor ORBs, other EJB servers,
and CORBA clients written in programming languages other than the Java programming language. For an
example application that uses an EJB server with a CORBA client, look at Enterprise JavaBeans Components and CORBA Clients.
New Java RMI-IIOP Features in J2SE 1.4
New command line argument for rmic tool allows programmers to construct
object implementations using the Portable Object Adapter (POA) that are portable
between different ORB products.
In the Java programming language, Portable Object Adaptor (POA)-based Dynamic
Skeleton Interface (DSI) servants inherit from the standard DynamicImplementation
class, which inherits from the Servant class. The native Servant type is
defined by the PortableServer
module for the POA. In the Java programming language,
the Servant type is mapped to the
org.omg.PortableServer.Servant class. It serves as the base class
for all POA servant implementations and provides a number of methods that
may be invoked by the application programmer, as well as methods which are
invoked by the POA itself and may be overridden by the user to control
aspects of servant behavior. For more information on the POA, see the CORBA/IIOP 2.3.1 Specification,
Chapter 11, formal/99-10-07.
New Object Request Broker Daemon, orbd. The orbd tool is a daemon
process containing a Bootstrap Service, a Transient Name Service, a Persistent Name Service,
and a Server Manager. For more information on the orbd tool, see the orbd manpage and Naming
Other new CORBA features include support for Portable Interceptors, an Interoperable
Naming Service, the General Inter-ORB Protocol (GIOP) 1.2, Dynamic Anys, and the new Server
Tool. For more information about these features, which are shared with the Java IDL technology, see Changes in CORBA Features Between J2SE 1.3 and
The OMG is the official
source of information for all CORBA and IIOP related information.
The CORBA 2.3.1 Specification is available electronically
from formal/99-10-07. The
URLs for the CORBA specifications may change. If this link is broken, link to
http://www.omg.org and search the specifications.
For more information on which specifications are implemented in this release of the Java
platform, see the compliance
For questions, please try the user supported forum for RMI-IIOP technology, which is available at
For general questions on the RMI-IIOP technology, please send email to
For comments on the tutorials, or to report errors in the tutorials,
please send email to email@example.com.