最简单的RMI调用示例
RMI是Remote Method Innovation的缩写，表示远程方法引进。
?
为不同机器之间提供服务。
第一步：定义接口。这个接口既是自己实现需要，也是远程需要的。两者定义应该是一样的。
?
?
package com.xiva.rmi;import java.rmi.Remote;import java.rmi.RemoteException;/** * @Description 接口必须扩展Remote接口，其方法必须throws RemoteException * @author Administrator * */public interface RoomService extends Remote{public String getRoomName(Long roomId) throws RemoteException; ;}?
第二步：实现接口。实现接口并写一个main方法启动服务。
?
?
package com.xiva.rmi;import java.rmi.RMISecurityManager;import java.rmi.RemoteException;import java.rmi.registry.LocateRegistry;import java.rmi.registry.Registry;import java.rmi.server.UnicastRemoteObject;/** * @Description 需要extends UnicastRemoteObject类 * @author Administrator * */public class RoomServiceImpl extends UnicastRemoteObject implements RoomService {protected RoomServiceImpl() throws RemoteException {super();}/** * */private static final long serialVersionUID = 1L;@Overridepublic String getRoomName(Long roomId) throws RemoteException{if(Long.valueOf(12l).equals(roomId)){return "废之间";}return "天之间";}public static void main(String[] args) {//System.setProperty("java.security.policy","*.policy");//设置安全策略 System.setSecurityManager(new RMISecurityManager());try { Registry reg = LocateRegistry.createRegistry(2011); //注册服务端口RoomServiceImpl pt = new RoomServiceImpl(); reg.rebind( "RoomService" , pt); //绑定服务名称System.out.println("Ready to do time"); } catch(Exception e) { e.printStackTrace(); } }}?
写好上面程序，就可以使用java来运行这个类了。
?
第三步，编写客户端程序。
?
?
package com.xiva.rmi.client;import java.rmi.Naming;import java.rmi.RMISecurityManager;import com.xiva.rmi.RoomService;public class CallRoom {public static void main(String[] args) { System.setSecurityManager( new RMISecurityManager()); try { RoomService t = (RoomService)Naming.lookup( "rmi://192.168.0.16:2011/RoomService"); System.out.println(t.getRoomName(11l));} catch(Exception e) { e.printStackTrace(); } } }?当然写完这些程序，在一般情况下是可以运行的。比如我的机器就可以正常运行。
?
但是有时我们是还需要指定keystore的，主要与环境有关系。有的计算机某些端口访问是需要提供验证，一般部署环境都是这样。
?
相关安全策略的设置：
?
D:\Program Files\Java\jdk1.6.0_29\jre\lib\security\java.policy
?
?
// Standard extensions get all permissions by defaultgrant codeBase "file:${{java.ext.dirs}}/*" {permission java.security.AllPermission;};// default permissions granted to all domainsgrant { // Allows any thread to stop itself using the java.lang.Thread.stop()// method that takes no argument.// Note that this permission is granted by default only to remain// backwards compatible.// It is strongly recommended that you either remove this permission// from this policy file or further restrict it to code sources// that you specify, because Thread.stop() is potentially unsafe.// See the API specification of java.lang.Thread.stop() for more // information.stopThread //permission java.lang.RuntimePermission "accessClassInPackage.sun.jdbc.odbc"; permission java.lang.RuntimePermission "stopThread"; permission java.lang.RuntimePermission "modifyThreadGroup"; permission java.lang.RuntimePermission "modifyThread"; permission java.net.SocketPermission "*", "connect,accept,resolve";// allows anyone to listen on un-privileged portspermission java.net.SocketPermission "localhost:1024-", "listen";// "standard" properies that can be read by anyonepermission java.util.PropertyPermission "java.version", "read";permission java.util.PropertyPermission "java.vendor", "read";permission java.util.PropertyPermission "java.vendor.url", "read";permission java.util.PropertyPermission "java.class.version", "read";permission java.util.PropertyPermission "os.name", "read";permission java.util.PropertyPermission "os.version", "read";permission java.util.PropertyPermission "os.arch", "read";permission java.util.PropertyPermission "file.separator", "read";permission java.util.PropertyPermission "path.separator", "read";permission java.util.PropertyPermission "line.separator", "read";permission java.util.PropertyPermission "java.specification.version", "read";permission java.util.PropertyPermission "java.specification.vendor", "read";permission java.util.PropertyPermission "java.specification.name", "read";permission java.util.PropertyPermission "java.vm.specification.version", "read";permission java.util.PropertyPermission "java.vm.specification.vendor", "read";permission java.util.PropertyPermission "java.vm.specification.name", "read";permission java.util.PropertyPermission "java.vm.version", "read";permission java.util.PropertyPermission "java.vm.vendor", "read";permission java.util.PropertyPermission "java.vm.name", "read"; permission java.util.PropertyPermission "file.encoding", "read";};?
?
设置为上面安全策略。
?
createRegister后，可以使用RMIGetRegister 来获取registry，bind新的服务名
?
/* * To change this template, choose Tools | Templates * and open the template in the editor. */package com.xiva;import java.rmi.AlreadyBoundException;import java.rmi.NotBoundException;import java.rmi.RemoteException;import java.rmi.registry.LocateRegistry;import java.rmi.registry.Registry;import java.rmi.server.UnicastRemoteObject;/** * * @author Administrator */public class RMIGetRegister { private static Registry registry = null; private static String bindName = "RoomService"; public static void main(String[] args) throws InterruptedException, RemoteException, AlreadyBoundException { // 取得RMIRegistry try { registry = LocateRegistry.getRegistry(2012); } catch (RemoteException ex) { System.out.println(ex.getMessage()); } // 解除Registry绑定 try { System.out.println("trying to unbind rmi registry"); registry.unbind(bindName); Thread.sleep(3000); //wait 3 seconds. } catch (RemoteException ex) { ex.printStackTrace(); } catch (NotBoundException ex) { //nothing to do } RoomService o = new RemoteServiceImpl(); //RemoteMethod stub= (RemoteMethod) UnicastRemoteObject.exportObject(o, 0); registry.bind("xiva", o); System.out.println("bindName"); }}?
注意UnicastRemoteObject.exportObject(o, 0)其中的o是没有extends UnicastRemoteObject的类。
?