RMI初探

接口

import java.rmi.Remote;
import java.rmi.RemoteException;public interface IFoo extends Remote {String say(String name) throws RemoteException;
}

import java.rmi.Remote;
import java.rmi.RemoteException;public interface IBar extends Remote {String buy(String name) throws RemoteException;
}

实现

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;public class FooImpl /* extends UnicastRemoteObject */ implements IFoo {private int index;public FooImpl() throws RemoteException {this(0);}public FooImpl(int port) throws RemoteException {// ObjectTable.objTableUnicastRemoteObject.exportObject(this, port);}@Overridepublic String say(String name) throws RemoteException {String message = "say" + (index++);System.out.println(message);return name + ": " + message;}
}

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;public class BarImpl implements IBar {private int index;public BarImpl() throws RemoteException {this(0);}public BarImpl(int port) throws RemoteException {// ObjectTable.objTableUnicastRemoteObject.exportObject(this, port);}@Overridepublic String buy(String name) throws RemoteException {String message = "buy" + (index++);System.out.println(message);return name + ": " + message;}
}

两个对象实例化之后, 观察 ObjectTable 类里的 objTable 和 implTable 属性内容

// sun.rmi.transport.ObjectTable
public final class ObjectTable {private static final Map<ObjectEndpoint, Target> objTable = new HashMap();private static final Map<WeakRef, Target> implTable = new HashMap();
}

ObjectTable.objTable 属性内容

ObjectTable.implTable 属性内容

Server

import java.net.MalformedURLException;
import java.rmi.AlreadyBoundException;
import java.rmi.Naming;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;public class Server {public static void main(String[] args) throws RemoteException, AlreadyBoundException, MalformedURLException {IBar bar = new BarImpl();IFoo foo = new FooImpl();//方式一Registry registry = LocateRegistry.createRegistry(58082);registry.bind("bar", bar);//方式二Naming.bind("rmi://192.168.31.141:58082/foo", foo);}
}

bind 方法会向 RegistryImpl的Hashtable<String, Remote> bindings属性put操作

执行Server的main方法之后, 服务端 registry 对象的属性如下

ObjectTable.objTable 属性内容里多了一个RegistryImpl_Stub

服务端会有一个线程(RMI TCP Accept-58082) 监听 58082 端口, 等待客户端的请求

客户端

import java.rmi.Naming;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;public class Client {public static void main(String[] args) throws Exception {//方式一Registry registry = LocateRegistry.getRegistry("192.168.31.141", 58082);IFoo foo = (IFoo) registry.lookup("foo");System.out.println(foo.say("druid"));//方式二IBar bar = (IBar) Naming.lookup("rmi://192.168.31.141:58082/bar");System.out.println(bar.buy("hikari"));}
}

参考文献

1. RMI源码调试