RMI实现分布式
现在虽然我们很少用到RMI进行编程，但是做为Java一个最早的分布式解决方案，我们还是有了解的必要，从例子开始吧（虽然是几年前的了）！

远程接口RmiHelloRemoteIntfc .java

import java.rmi.*;

public interface RmiHelloRemoteIntfc extends Remote
{
String helloRemoteObj(String client) throws RemoteException;
}

远程接口的实现类RmiHelloRemoteObj.java

import java.rmi.server.*;
import java.rmi.*;

public class RmiHelloRemoteObj extends UnicastRemoteObject implements RmiHelloRemoteIntfc
{

public RmiHelloRemoteObj() throws RemoteException
{
super();
}

public String helloRemoteObj(String client) throws RemoteException
{
return "Hello World"+client;
}

}

服务器类RmiHelloServer.java

import java.io.*;
import java.rmi.*;
import java.rmi.server.*;
import sun.applet.*;
import java.rmi.registry.LocateRegistry;

public class RmiHelloServer
{

public RmiHelloServer()
{
}
public static void main(String[] args)
{
//创建并安装安全管理器
if(System.getSecurityManager()==null)
{
System.setSecurityManager(new RMISecurityManager());
}

try{
//创建远程对象
RmiHelloRemoteObj ttt=new RmiHelloRemoteObj();
//启动注册表
LocateRegistry.createRegistry(2222);
//奖名称绑定到对象
Naming.rebind("//Fangm:2222/helloObj",ttt);

System.out.println("RMI服务器正在运行。。。。。。");
}
catch(Exception e)
{
e.printStackTrace();
}


}
}

服务器端的权限文件RmiHelloServer.policy

grant codeBase
"file:/e:/download/rmitest/"
{
permission java.net.SocketPermission
"*:1000-9999","accept,connect,listen,resolve";
};



现在就看看Client端是如何连接服务器和进行远程方法的调用的吧


import java.rmi.*;
import java.rmi.server.*;

public class RmiHelloClient
{

public RmiHelloClient()
{
}
public static void main(String[] args)
{
//创建并安装安全管理器
if(System.getSecurityManager()==null)
{
System.setSecurityManager(new RMISecurityManager());
}

try{
RmiHelloRemoteIntfc c1=(RmiHelloRemoteIntfc)Naming.lookup("rmi://Fangm:2222/helloObj");
System.out.println(c1.helloRemoteObj("Everyone"));
}
catch(Exception e)
{
e.printStackTrace();
}
System.exit(0);



}
}

Client端的权限文件RmiHelloClient.policy

grant codeBase
"file:/e:/download/rmitest/"
{
permission java.net.SocketPermission
"*:1000-9999","accept,connect,listen,resolve";
};

好了，一个最简单的RMI例子就安无了，对了还少了最重要的一步，那就是编译和运行呢？我们就来了个Bat或Cmd的批处理来进行吧，

看看RmiHello.bat吧

javac RmiHelloRemoteIntfc.java

javac RmiHelloRemoteObj.java

rmic RmiHelloRemoteObj

javac RmiHelloServer.java

javac RmiHelloClient.java

echo 在另一个窗口启动服务器，请稍后。。。
start java -Djava.security.policy=RmiHelloServer.policy RmiHelloServer

echo 运行客户程序。。。
java -Djava.security.policy=RmiHelloClient.policy RmiHelloClient

这个文件很简单吧！包你一试就通，虽然简单，不过对于初学者来说，还是很不错的哦！