Question

我在尝试使用RMI在服务器和客户端之间运行通信时遇到了麻烦。我的代码附在下面。服务器运行正常，我可以在pc端口列表中看到监听端口，客户端在registry.lookup上失败。我没有发现任何类似的问题。请帮忙。

服务器：

public class Main {

private static int port = Registry.REGISTRY_PORT; 
private static Registry registry;
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {

   if (args.length == 1) {
        try {
                port = Integer.parseInt(args[0]);
                }
            catch (NumberFormatException e) {
    System.out.println("Port number is not valid!");
    System.exit(0);
            }
}

    if (System.getSecurityManager() == null)
        System.setSecurityManager(new RMISecurityManager());
String name = "DBInterface";

    System.out.println("Starting server.");

    try {        
        DBInterface DBInterface = new DBClass();
        DBInterface stub = (DBInterface) UnicastRemoteObject.exportObject(DBInterface, 5000); 
        registry = LocateRegistry.createRegistry(port);
        registry.rebind(name, stub);
    }
    catch (RemoteException e)
    {
        System.out.println(e.getMessage());
    }
    System.out.println("Server succesfully started.");

}

}

客户端：

public class Client {

private static String ipAddress = "localhost";
private static int port = Registry.REGISTRY_PORT;
private static String confFile = "";
public static DBInterface dbServer = null;
public static String name = "DBInterface";

public static void main(String[] args) {
    System.out.println("Starting client.");

    if (System.getSecurityManager() == null)
        System.setSecurityManager(new RMISecurityManager());


    if (args.length == 3) {
        try {
            ipAddress = args[0];
            port = Integer.parseInt(args[1]);
            confFile = args[2];
        }
        catch (NumberFormatException e) {
    System.out.println("Port number is not valid!");
    System.exit(0);
        }
}
    else
    {
        System.out.println("Some parameter is missing!");
        System.out.println("Valid parameters are: IP(0) Port(1) Config_file_name(2).");
    }

    ArrayList<ArrayList<String>> commands = Tools.loadConfigFile(confFile);
    Iterator<ArrayList<String>> commandsIterator = commands.iterator();
    Registry registry;

try {
        registry = LocateRegistry.getRegistry(ipAddress, port);    
        dbServer = (DBInterface) registry.lookup(name);  //code fails here                   
} catch (RemoteException e) { 
        System.out.println(e.getMessage());  //"no such object in table" is printed on the screen
} catch (NotBoundException e) {
        System.out.println(e.getMessage());
}        
    Tools tools = new Tools(dbServer);

...

Answer 1

你所描述的基本上是不可能的。该异常意味着您正在使用的存根（在本例中为Registry）不再引用目标JVM中的实时导出对象。但是，由于注册表存根是在本地创建的，因此它们根本没有机会到期。唯一的机制是您创建的注册表退出，但静态注册表引用应该阻止它。

我会改变一些事情：

    DBInterface stub = (DBInterface) UnicastRemoteObject.exportObject(DBInterface, 5000); 
    registry = LocateRegistry.createRegistry(port);

反转这两行，并对注册表和导出使用port。您不需要两个端口。此外，在所有的catch块中，永远不要只是压缩异常消息而不是你自己的。您应始终至少记录实际的异常消息。

调用registry.lookup时，表中没有这样的对象

1 个答案: