Colby Fall 2008 Java RMI教程：分布式HelloWorld示例与实践

需积分: 2 70 浏览量更新于2024-07-09 收藏 4.65MB PDF 举报

Java RMI (Remote Method Invocation)教程是针对Java虚拟机间对象远程调用的重要指南。RMI系统使得一个Java程序能够在另一个Java虚拟机上执行方法，实现跨平台的分布式计算。在这个教程中，作者分享了自己在Colby大学秋季2008年使用Java RMI进行实践的经验，主要探讨的是如何运行、修改和重新部署一个简单的分布式HelloWorld示例，该示例取材自Sun Microsystems提供的官方文档。 HelloWorld示例的核心是客户端与服务器之间的交互。在这个场景中，有两台机器：一台作为服务器（通常称为lowercase server），另一台作为客户端（同样称为lowercase client）。服务器上运行的Java程序名为Server（大写），它包含可以通过网络连接调用的方法，使其成为远程对象。客户端则运行名为Client的Java程序，通过RMI机制来访问服务器上的远程对象。为了建立服务器和客户端之间的通信，服务器上还需要运行一个RMI注册表（RMI registry），它负责管理远程对象的注册和查找。当客户端试图调用服务器上的方法时，它首先会与注册表交互，查询并获取服务器上特定远程对象的URL。图1展示了这个过程，其中RMI注册表和Server在服务器上运行，而Client在客户端运行。具体步骤包括： 1. **创建远程接口（Remote Interface）**：定义服务器端对象的行为和方法，这些方法将成为可以被远程调用的接口。 2. **实现远程接口（Implementing the Remote Interface）**：在Server程序中实现远程接口，并声明为远程类。 3. **注册远程对象**：在Server启动时，将远程对象注册到RMI注册表，指定其名称和位置。 4. **编写客户端代码**：在Client程序中，创建一个远程对象的引用，通过URL找到并调用远程方法。 5. **客户端与服务器连接**：通过网络连接，Client通过RMI注册表找到服务器上的远程对象，调用其方法。 6. **结果处理**：服务器返回的结果通过网络传回给客户端，完成一次跨平台的远程调用。 7. **测试和调试**：在实际环境中反复测试，确保客户端能够正确地找到和调用服务器上的方法，以及处理可能的异常情况。这份教程不仅提供了基础的HelloWorld示例，还可能深入讲解RMI的安全性、性能优化以及错误处理等相关知识点，有助于读者深入了解Java RMI在实际项目中的应用和最佳实践。

 Next, the Client “locates” the rmiregistry on the server. This is a bit of a misnomer

because no communication is actually done here. The call merely sets up the necessary data

structures for later calls which do require communication, such as the lookup on the next line.

 This Client wants to call a method on Server. To do this it needs the stub (which is on the

server). To get it, it asks the rmiregistry on the server to lookup the string name “Hello”

and send the stub over the internet/intranet. The stub is cast to a Hello type.

 Next is the actual remove method invocation. The sayHello method on the stub is called,

the sub sends the request to the server, the server executes its sayHello method and

returns a String which is then sent across the inter/intranet to the client.

 Finally, Client proudly prints the result from the remote method invocation. In this case, it

will be “Hello, world!”.

Compiling “Hello World”

The “Hello World” example involves a server and one or more clients. I am planning to continue using

this model – I intend to run my machine as the server and use other machines as clients. I will write all

code on my computer, then deploy code to the clients as necessary (i.e. only those classes necessary

to run the Client will ever make it to the client machine).

Given this setup, compiling is trivial. All of the “Hello World” code is in the subdirectory example/hello.

From a terminal window, I change directory (cd) to example/hello and type

javac Hello.java Client.java Server.java

This results in the creation of Hello.class, Client.class, and Server.class. Only

Client.class and Hello.class are needed on the client. To make it easy to deploy the compiled

code, I will package the two class files together using the Java archive tool jar. This will combine and

compress the files (using ZIP). At the command line, I type

cd ../../

jar cvf HelloClient.jar example/hello/Hello.class \

example/hello/Client.class

and the file HelloClient.jar is created with appropriate directory structure. See Figure 2 for the

Terminal output and Figure 3 for the directory structure.

Figure 2: Terminal with compilation commands and output.

剩余17页未读，继续阅读

Howard-Cheng

粉丝: 32
资源: 51

Colby Fall 2008 Java RMI教程：分布式HelloWorld示例与实践

Java RMI Tutorial

Java RMI

Java RMI学习资料

javaRMI规范.pdf

RMI.rar_Java RMI_java.rmi_java.rmi.Remot_remote

Java RMI.pdf

JavaRMI.pdf

[Java RMI].zip

TutorialsPoint Java RMI 教程.epub

rmi.rar_Java RMI_RMI java_RMI policy.all_rmi

最新资源