RMI远程调用

第一步：远程对象接口
WareHose.java

package server;
import java.rmi.Remote;
import java.rmi.RemoteException;

public interface WareHose extends Remote{
	
	public Double getPrice(String description)throws RemoteException;
	
}

第二步：实现远程对象接口

package server;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.HashMap;
import java.util.Map;

public class WareHoseImpl extends UnicastRemoteObject implements WareHose{
	private static final long serialVersionUID = -5446129893581781406L;
	
	private Map<String,Double> map = null;
	
	public WareHoseImpl() throws RemoteException {
		super();
		map = new HashMap<String,Double>();
		map.put("Apple", 6.5);
		map.put("orange", 8.9);
		//如果WareHoseImpl已经继承了其他的类可用在构造函数中使用
		//UnicastRemoteObject.exportObject(this, 0);第二个参数0表示可在服务器任意端口上监听远程调用请求
	}
	
	@Override
	public Double getPrice(String description) throws RemoteException {
		return map.get(description);
	}
}

第三步：将远程对象注册到RMI注册表中

package server;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class RegisterRmiServer {
	private final static void register(String name,Object obj) throws NamingException{
		Context namingContext = new InitialContext();
		if(name != null)
			//绑定的url格式为rmi://主机名:端口号/RMI注册对象的名称  次名称用于唯一表示远程对象客户端可通过此名称找到远程对象
			//不写主机和端口号的话默认为localhost:1099
			namingContext.bind("rmi:RemoteObject_"+name, obj);
		else
			namingContext.bind("rmi:"+obj.getClass().getSimpleName(), obj);
	}
	public final static void start(List<Object> list){
		for(Object obj : list){
			try {
				register(null, obj);
			} catch (NamingException e) {
				e.printStackTrace();
			}
		}
	}
	public final static void start(Map<String,Object> map){
		for(Entry<String, Object> entry : map.entrySet()){
			try {
				register(entry.getKey(), entry.getValue());
			} catch (NamingException e) {
				e.printStackTrace();
			}
		}
	}
	public static void main(String[] args) throws Exception{
		List<Object> list = new ArrayList<Object>();
		WareHoseImpl wHose = new WareHoseImpl();
		list.add(wHose);
		RegisterRmiServer.start(list);
	}
}

第四步：创建客户端访问远程对象

package client;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NameClassPair;
import javax.naming.NamingEnumeration;

import server.WareHose;

public class AccessRemoteObject {
	public static void main(String[] args) throws Exception{
		Context namingContext = new InitialContext();
		NamingEnumeration<NameClassPair> e = namingContext.list("rmi://localhost/");
		while(e.hasMore()){
			System.out.println(e.nextElement().getName());
		}
		WareHose wareHose = (WareHose)namingContext.lookup("rmi:WareHoseImpl");
		System.out.println(wareHose.getPrice("orange"));
	}
}

第五步：启动RMI注册表(Window下)
在java安装路径下bin目录下有一个rmiregistry.exe服务
由于类：RegisterRmiServer.java在注册远程对象到RMI注册表中的时候rmiregistry需要加载远程对象的.class字节码文件，这里涉及到一个classpath的问题

cmd>set classpath=%classpath%;远程对象的.class文件顶级包所在的目录
cmd>rmiregistry

上述命令要在同一个cmd窗口下执行

接下来可以用main方法测试效果