Question

尝试在客户端查看远程对象的属性时出现上述错误。在论坛（http://www.java-forums.org/networking/69581-rmi-classcastexception-proxy-cannot-cast.html）上阅读帖子之后，我认为这是因为远程对象在客户端和服务器中的不同包名中，所以我将客户端程序（甚至是远程接口）移到了与服务器和远程对象本身相同的包。但我仍然有同样的错误：

线程“main”中的异常java.lang.ClassCastException：com.sun.proxy。$ Proxy0无法强制转换为uk.ac.rm950.nonPublicDataSerializationServer.Employee at uk.ac.rm950.nonPublicDataSerializationServer.ClientSideProgram.main（ClientSideProgram.java:26）

这是我的远程界面：

package uk.ac.rm950.nonPublicDataSerializationServer;

public interface ObjectTransporter<T> extends java.rmi.Remote {
public T fetchObject() throws java.rmi.RemoteException;
}

远程对象类如下所示：

package uk.ac.rm950.nonPublicDataSerializationServer;

import java.rmi.RemoteException;

//import uk.ac.rm950.remoteInterface.ObjectTransporter;

public class Employee implements ObjectTransporter<Employee> {

public String name;

public Employee(String name) {
this.name = name;
}

@Override
public Employee fetchObject() throws RemoteException {
return this;
}
}

这是服务器程序：

package uk.ac.rm950.nonPublicDataSerializationServer;

import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;

//import uk.ac.rm950.remoteInterface.ObjectTransporter;

public class ServerSideProgram {

public static void main(String[] args) {
System.setProperty("java.security.policy", "security/server.policy");

if (System.getSecurityManager() == null) {
System.setSecurityManager(new SecurityManager());
}

try {
Registry registry = LocateRegistry.createRegistry(1099);

ObjectTransporter<Employee> transportingObject = new Employee("Nemo");
ObjectTransporter<Employee> stub = (ObjectTransporter<Employee>) UnicastRemoteObject.exportObject(transportingObject, 0);
registry.rebind("employee", stub);

System.out.println("Employee object bound.");
} catch (RemoteException e) {
System.out.println("Exception occurred on server side.");
e.printStackTrace();
}}}

这是客户端代码：

 package uk.ac.rm950.nonPublicDataSerializationServer;

 import java.rmi.NotBoundException;
 import java.rmi.RemoteException;
 import java.rmi.registry.LocateRegistry;
 import java.rmi.registry.Registry;

 //import uk.ac.rm950.remoteInterface.ObjectTransporter;

 public class ClientSideProgram {

 public static void main(String[] args) {
 System.setProperty("java.security.policy", "security/server.policy");

 if (System.getSecurityManager() == null) {
 System.setSecurityManager(new SecurityManager());
 }

 try {
 Registry registry = LocateRegistry.getRegistry();
 ObjectTransporter<Employee> transportedObject = (ObjectTransporter<Employee>) registry.lookup("employee");

 //  Employee deserializedEmployee = (Employee) transportedObject.fetchObject();
 System.out.println(transportedObject.fetchObject().name);  
 } catch (RemoteException e) {
 e.printStackTrace();
 } catch (NotBoundException e) {
 e.printStackTrace();
 }}}

当客户端程序执行时抛出错误，我无法弄清楚我做错了什么。

Answer 1

您正在尝试将存根转换为远程对象本身。你不能。事实并非如此。你应该把它投射到远程接口：

ObjectTransporter<Employee>

RMI异常：代理无法强制转换为远程对象

1 个答案: