Its popularity notwithstanding, RMI thus far has been limited to distributed systems that operate within the confines of a single administrative domain. The main reason for that limit: RMI lacked the security features required of wide-area distributed systems—especially systems that perform method invocations across the public Internet. Access to RMI calls' customization features was not part of the standard RMI API, and existing RMI implementations did not provide programmatic access to securing RMI method invocations. |
In Jini, a software component makes its services available through a proxy. Other services must locate that proxy to interact with a service within djinn, a federation of Jini services. Jini offers a robust mechanism, based on the Java language interfaces implemented by the proxy, that helps you look up proxies and other optional parameters. However, the ubiquitous computing environments promised by Jini and other service-oriented architectures require a service that is easily locatable and readily available. |
Your first thought may be, Why bother to do this in the first place; why not just use Jini? We would agree with this logic, especially for new systems. However, many RMI-based systems still exist, and until Jini is accepted into mainstream Java development, we need to provide more elegant RMI solutions. In fact, the work described here is the result of such a requirement: to develop a Jini service that can also run as a standalone RMI server, but uses Jini-like discovery. |
CORBA's service context provides an efficient and elegant design and implementation approach for building distributed systems. Java RMI (Remote Method Invocation) can't easily support transparent service-context propagation without instrumenting the underlying protocol. This article describes a generic lightweight solution for supporting transparent and protocol-independent service-context propagation over RMI. Reflection-based techniques are used to emulate what's normally seen in protocol-specific service-context implementations. |
This article presents a simple and elegant solution to the many problems associated with RMI-based product development. The article assumes you have a reasonably good understanding of RMI-based client/server development. |
Learning Command Objects and RMI -- O'Reilly's Java RMI author William Grosso introduces you to the basic ideas behind command objects by providing a translation service from a remote server and using command objects to structure the RMI made from a client program. |
In this article, I introduce the basic ideas behind command objects. In order to do so, I drag in an example application that provides a translation service from a remote server. After introducing this application, I will show how to use command objects to structure the remote method invocations (RMI) made from a client program. As part of this article, I will introduce a fairly general framework for encapsulating remote method calls in command objects. |
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As for interoperability between J2EE servers, again its just hype. The lack of security and interoperable OTS implementations basically means that you'll run into issues here also. JMS or SOAP are probably your best bets for achieving interoperability between different J2EE products in the near and medium terms. So, at least from my perspective, it started out as a good idea but unfortunately, lack of standards and the other issues highlighted here show that the reality is slightly different. |
Java Remote Method Invocation (RMI) introduced a powerful mechanism for distributing application logic across different machines. Instead of having to perform tasks in one monolithic central system, RMI made it possible to build modular and manageable applications where the computing logic could be distributed. RMI has been the primary communication mechanism for various server-side component architectures, including Enterprise JavaBeans (EJB). Introduced with Java 1.1, RMI has been steadily evolving with every major release and has seen the introduction of three new important features with the release of Java 5.0. The new features include support for dynamic stub generation, RMI over SSL, and the ability to launch a Java RMI sever as an extended Internet service (xinetd) daemon in Unix systems. In this article we will cover these additions. |
This is good news for RMI fans -- it simplifies both development and deployment without incurring any real cost. The changes in 1.5 also started me to thinking about the changes in RMI over the past few releases. When RMI first shipped, it looked a lot like CORBA. A lighter-weight and Java-specific CORBA, to be sure, but with the exception of dynamic codeloading, it had the same feel, and the same basic structure -- you define interfaces, create stubs and skeletons, and so on. |
Part 1 of this series introduced the syntax and semantics of the JavaFX Script programming language to the Java technology programmer. This article will draw on your knowledge of JavaFX Script, invoking the Java platform's Remote Method Invocation (Java RMI) libraries to allow a JavaFX graphical user interface (GUI) to communicate remotely. Using RMI with JavaFX Script is very straightforward, and it provides a quick and easy way to demonstrate and test client-server functionality with JavaFX Script technology. |
Java RMI (remote method invocation) technology makes it very easy to create web-based applets that perform powerful server-side operations, such as accessing a database or communicating with remote server applications. However, a number of RMI limitations make its use in Internet-based applets impractical. This article describes a way to work around these limitations by using Java servlets and object serialization for applet/server communication, and demonstrates several ways to use this technique. The focus of this article is on converting an existing application, but the same design can used when creating new applications. |
James Gosling: Oddly enough, something very much like the Jini world was in there from day one. The very early version of Java, which was called Oak and ran on the Star Sevens, had a distributed message system in it that was very much like RMI. |
As previously mentioned, Burlap/Hessian serializes Java objects using a proprietary serialization mechanism. The serialization process is completely transparent to the application (i.e., you do not need to implement any special interfaces to make objects serializable). Burlap/Hessian serialization is very efficient, and the produced serialized object snapshots (either XML or binary) are very compact. |
This article provides practical demonstrations for using RMI and EJB technologies, both individually and in tandem. It pays particular attention to the problems that arise when sharing EJB and RMI and discusses the scenarios where one is a better choice than the other. All the working methods include simple examples and diagrams that illustrate the working principles behind these technologies. |
An Overview of RMI Applications describes the RMI system and lists its advantages. Additionally, this section provides a description of a typical RMI application, composed of a server and a client, and introduces important terms. |
IBM and Sun Microsystems launched a joint initiative in 1997 to promote the advancement of Java as an enterprise-development technology. In particular, the two companies focused on how Java could be used as a server-side language, producing enterprise-level code that could be incorporated into existing architectures. What was needed was a remote transport technology that combined the small footprint of Java's RMI (Remote Method Invocation) and the sturdiness of the more mature CORBA (Common Object Request Broker Architecture) technology. Out of this need was born RMI-IIOP, which has helped propel the Java language into its current position as the leading language for server-side enterprise development. |
This is where value objects come in. Value objects are simple Java classes that can be used to represent many kinds of objects, including data in a relational database row. By using the value object directly, instead of repeatedly using the bean's remote interface, we can reduce our RMI traffic to a single method invocation. |
Brad Rubin guides you through the basics of distributed computing, which lets you maximize computing potential with data sharing, improved performance, and enhanced function placement. He covers RMI and CORBA, showing how they are implemented in the Java? programming language, and uses plenty of code examples to illustrate the concepts. |
With an activatable service implementation, the stub will try to contact the object via a live remote reference, just as it would with a nonactivatable implementation. If the reference is not valid, the stub will use a second reference, this time to the activation system running on the remote object's host. This activation system is stored in the stub as an internal RMI reference. If it receives a request to activate an object, the stub will return to the caller -- the Jini client, in our case -- a live reference to the remote object. Thus, this second remote call will return a valid service reference to our applet. This is called a faulting remote reference, since it allows the activation system to "fault in" the object on demand. This process is transparent to the client and is solely an implementation issue of the service. |
The persistent RMI Server instantiates the base of common-memory, FrameWorkBase and assigns a class field to the reference of the FrameWorkBase object. Since the reference is live and the Server is persistent, Java? does not garbage collect the object. Think of the start up class fields as anchor points. |
These are the classes. Compile all the java files to get the class files. Now, use the RMI compiler to generate the stub. Use the .keep option if you need the source file of the stub. |
Building a four-tier Web solution is not as difficult as it sounds. Two of today's Internet technologies make piecing together a scalable, robust Web interface to a database a simple matter of assembling small, customized elements. All the hard work goes on behind the scenes. |
For developing a distributed Internet application, the Java-RMI (Remote Method Invocation) solution is easier to deploy than the alternatives (CORBA and DCOM). However, the benefits of the quick and easy implementation are tempered by a deficiency in a functionality that is critical for most enterprise systems -- multi-language support. Since the Java-RMI solution is less robust then its counterparts, it is best-suited for small, 100% Java applications where legacy database integration is not a requirement and scalability issues are not major concerns. |