分布式计算原理与应用课后习题第七章.doc

6. 修改后的HelloImpl.java 代码：import java.rmi.RemoteException;import java.rmi.server.UnicastRemoteObject;public class HelloImpl extends UnicastRemoteObject implements HelloInterface /conductorprotected HelloImpl() throws RemoteException super();public String sayHello(String name) throws RemoteException try Thread.sleep(5000);/延迟5秒 catch (InterruptedException e) e.printStackTrace(); return Hello ,+ +name+!; 运行结果如下图：客户1：客户2： 由运行结果显示，第一个用户需要等待5秒才得到结果，而第二个等待的时间小于5秒，由此可推测该方法调用是并行执行的。8.代码如下：（1） DaytimeInterface接口import java.rmi.Remote;import java.rmi.RemoteException;public interface DaytimeInterface extends Remote public String sayTime(String name) throws RemoteException ;（2） DaytimeImpl接口实现类import java.rmi.RemoteException;import java.rmi.server.UnicastRemoteObject;import java.util.Date;public class DaytimeImpl extends UnicastRemoteObject implements DaytimeInterface protected DaytimeImpl() throws RemoteException super(); public String sayTime(String name) throws RemoteException Date timestamp = new Date (); return timestamp.toString(); （3） DaytimeServer服务器类import java.io.BufferedReader;import java.io.InputStreamReader;import .MalformedURLException;import java.rmi.Naming;import java.rmi.RemoteException;import java.rmi.registry.LocateRegistry;import java.rmi.registry.Registry;public class DaytimeServer public static void main(String args) InputStreamReader is = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(is); String portNum, registryURL; try /注册服务器不在运行状态时，用户指定端口启动RMI注册服务器 System.out.println(Enter the RMIregister port number :); portNum = (br.readLine().trim(); int RMIPortNum = Integer.parseInt(portNum); startRegistry(RMIPortNum); /以URL的形式将分布式对象的引用存储到注册表当中 DaytimeImpl exportedObj = new DaytimeImpl(); registryURL = rmi:/localhost: + portNum + /saytime; Naming.rebind(registryURL, exportedObj); System.out.println(Server registered . Registry currently contains:); listRegistry(registryURL); System.out.println(DaytimeServer ready.); catch (Exception re) System.out.println(Exception in HelloServer in main : + re); /list the names of registered with a Registry object private static void listRegistry(String registryURL) throws RemoteException, MalformedURLException System.out.println(Registry + registryURL + contains :); String names = Naming.list(registryURL); for(int i = 0 ; i names.length; i+) System.out.println(namesi); /start a registry if it does not exists a specified port number private static void startRegistry(int RMIPortNum) throws RemoteException try Registry registry = LocateRegistry.getRegistry(RMIPortNum); registry.list(); catch(RemoteException e) System.out.println(RMI registry cannot be located at port + RMIPortNum); System.out.println(RMI registry created at port + RMIPortNum); （4） DaytimeClient客户类import java.io.BufferedReader;import java.io.InputStreamReader;import java.rmi.Naming;public class DaytimeClient public static void main(String args) try String hostName; String portNum; InputStreamReader is = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(is); System.out.println(Enter the RMIRegistry host name :); hostName = br.readLine(); System.out.println(Enter the RMIRegistry port number :); portNum = br.readLine(); String registryURL = rmi:/ + hostName + : + portNum + /saytime; DaytimeInterface h = (DaytimeInterface)Naming.lookup(registryURL); System.out.println(Lookup completed); String message =