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分布式对象-如何使用RMI和CORBA,在java中

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<td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>用于分布式对象编程的技术</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>   第 6 页（共8 页）</nobr></font></td>
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<p>有各种各样的技术可以用于通信信息、远程执行代码和协调同一台机器上的进程或远程机器的进程之间的处理。</p>
<p>最早的且仍常见的技术之一是：在进程之间打开一条通信链路。一旦建立这条链路，一个进程就能向另一个进程发送编码某些操作和信息的数据流，而接收进程会对数据流进行解码并执行操作，通常再用同一技术将结果返回给发起进程。套接字编程是这一技术的一个示例；在客户机和服务器之间传递经过编码的 HTML 信息的 HTTP 协议是另一个示例。</p>
<p>这一技术的问题是：程序员必须为每个应用程序创建一个编码协议和命令的方案。这一技术还产生两种不同的编程范例：源于编程语言的调用过程／传递参数模型和用于套接字编程的命令模型。这两种编程范例使得编程更加困难。此外，两台机器之间的数据格式和字节排列顺序假设都可能不同，使代码更为复杂。</p>
<p>另一个常见模型是&ldquo;远程过程调用（RPC）&rdquo;。这里，程序员可以调用一个远程过程并来回地传递参数，就象他们进行本地过程调用那样。这使得本地编程和分布式编程都能使用相同的编程风格。</p>
<p>尽管如此，仍存在数据格式和字节排列顺序的问题，而且 RPC 不符合面向对象模型。</p>
<p>让我们看一看作为一种解决方案的 RMI。</p>
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