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This topic includes the following sections:

• What is RMI?

• What is WebLogic RMI on IIOP?

• What about RMI clients of EJBs?

• Where can I learn more about RMI?

• What software and development environment do I need for WLE RMI?

• What is next?

What is RMI?

Remote Method Invocation (RMI) is a Java based programming paradigm and application programming interface (API) for distributed object computing and Web connectivity. RMI allows an application to obtain a reference to an object that exists elsewhere on the network but then invoke methods on that object as though it existed locally on the client's Java virtual machine. So, products, services, and resources can exist anywhere on the network but appear to the programmer and the end user to be part of the local environment.

With RMI, a client object can call a remote object in a server, and that server can also be a client of other remote objects.RMI uses some form of Java serialization to marshal (encode) and unmarshal (de-code) parameters sent across a network. Serialization is a way of encoding parameters into a byte stream for delivery across a network.

What is WebLogic RMI on IIOP?

The BEA WebLogic Enterprise (WLE) development platform provides remote method invocation (RMI) as one of the standard services of a Java 2 Enterprise Edition (J2EE) implementation. For this release, WLE provides its own protocol of WebLogic RMI on the Object Management Group's industry-standard Internet Inter-Orb Protocol (IIOP). IIOP is a protocol that enables browsers and servers to exchange integers, arrays, and more complex objects, unlike HTTP which supports only transmission of text.

The primary advantage of the WLE implementation of RMI on IIOP is that it allows application developers to write remote interfaces between WLE clients and EJB servers, using a natural Java API. By making a few code enhancements, developers can also convert their legacy Java client/RMI server applications to work in WLE. WLE RMI clients can talk to EJBs and traditional RMI server objects.

WLE RMI has the following characteristics and capabilities:

• Flows over an IIOP transport-Firewalls configured to support IIOP traffic will accept WebLogic RMI on IIOP messages as standard IIOP messages.

• Uses the J2EE JNDI service for bootstrapping-In order for a client program to make a call on a remote object, the client needs to obtain a reference to the remote object. Traditional RMI uses the Java Naming Service to do this. In WLE RMI, a client gets a reference to a remote object by looking it up via the J2EE Java Naming and Directory Service (JNDI). A client can also get a reference to a remote object by receiving the reference as an argument or a return value.

• Enables clients to talk to EJBs-All clients of EJBs use RMI on IIOP

• Provides support for maintaining a transaction context between clients and remote EJBs or RMI servers-The WebLogic Enterprise system supports the Java Transaction API (JTA)

For this release, WLE IIOP does not pass Objects by Value which is needed for full CORBA interoperability support. Instead, WLE RMI on IIOP passes serialized objects as in traditional RMI. Therefore, this release of WLE does not support complete interoperability between Java clients, EJBs, and CORBA objects.

What about RMI clients of EJBs?

All clients of Enterprise Java Beans (EJB) use RMI on IIOP. Creating a client to an EJB server is essentially the same as creating an RMI client to a traditional RMI server. For more information on this, see the topic Using RMI with EJBs. For examples of clients of EJBs using RMI on IIOP to talk to EJB servers, see the WebLogic Enterprise 5.0 EJB Sample Applications in the WebLogic Enterprise online documentation.

Where can I learn more about RMI?

For more information about remote method invocation, refer to the The Sun Microsystems, Inc. Java site at http://java.sun.com/.

What software and development environment do I need for WLE RMI?

Before you can start developing WLE RMI applications, you need the following:

• WLE installed on your system

• Java Development Kit (JDK) 1.2 installed on your system

• Environment variables set appropriately

• CLASSPATH and PATH set to include the appropriate WLE and JDK pathnames

For information on installing WebLogic Enterprise, see the product installation guide.

For more information on setting up your development environment, see the topic Setting Up Your WLE Development Environment.

For information on the JDK, refer to the The Sun Microsystems, Inc. Java site at http://java.sun.com/.

What is next?

The following topics are covered in this guide for WebLogic Enterprise RMI on IIOP:

• Getting Started with RMI - a Hello World Example-If this is your first time using RMI, or if the WLE development environment is new to you, we suggest that you start by working through the Hello World example. This covers the basics of using remote objects in the WebLogic Enterprise environment.

• Developing RMI Applications in WLE-This section details the steps you need to follow to develop, build and run RMI applications in WLE. The Hello World example is used as a touchstone.

• Using RMI with Client-Side Callbacks

• Using RMI with EJBs

• Converting Sun JavaSoft RMI to WLE RMI Classes

• The WebLogic Enterprise RMI API

For more information about using transactions in your RMI applications, see Using Transactions in the WebLogic Enterprise online documentation.