Java RMI代理问题 [英] Java RMI Proxy issue
问题描述
我收到此错误:
java.lang.ClassCastException: $Proxy0 cannot be cast to rmi.engine.Call
at Main.main(Main.java:39)
我的 Abstract
和调用
类都扩展远程
。
致电:
public class Call extends UnicastRemoteObject implements rmi.engine.Abstract {
public Call() throws Exception {
super(Store.PORT, new RClient(), new RServer());
}
public String getHello() {
System.out.println("CONN");
return "HEY";
}
}
摘要:
public interface Abstract extends Remote {
String getHello() throws RemoteException;
}
这是我的主要:
public static void main(String[] args) {
if (args.length == 0) {
try {
System.out.println("We are slave ");
InetAddress ip = InetAddress.getLocalHost();
Registry rr = LocateRegistry.
getRegistry(ip.getHostAddress(), Store.PORT, new RClient());
Object ss = rr.lookup("FILLER");
System.out.println(ss.getClass().getCanonicalName());
System.out.println(((Call)ss).getHello());
} catch (Exception e) {
e.printStackTrace();
}
} else {
if (args[0].equals("master")) {
// Start Master
try {
RMIServer.start();
} catch (Exception e) {
e.printStackTrace();
}
}
Netbeans说问题出在第39行,即
Netbeans says the problem is on line 39 which is
System.out.println(((Call)ss).getHello());
输出如下:
运行:
We are slave
Connecting 10.0.0.212:5225
$Proxy0
java.lang.ClassCastException: $Proxy0 cannot be cast to rmi.engine.Call
at Main.main(Main.java:39)
BUILD SUCCESSFUL (total time: 1 second)
我正在cmd上监听端口5225上运行一个主人。
I am running a master in cmd listening on port 5225.
推荐答案
类 $ Proxy0
是动态代理,即java在运行时生成一个类。
The class $Proxy0
is a dynamic proxy, that is, a class is generate by java at run-time.
此类应实现接口 Abstract
,但不扩展调用
。所以你不能将它转发到调用
(这会给出一个类强制转换),但是将它向下转换为 Abstract
应该是好的。
This class should implement the interface Abstract
, but does not extend Call
. So you can't downcast it to Call
(this gives a class cast), but downcasting it to Abstract
should be ok.
如果你使用RMI,你应该只通过接口与远程对象通信。
If you use RMI, you should only communicate with remote object through interfaces.
PS:抽象
是一个令人困惑的名字。我真的以为你说的是抽象课程第一。如果可能的话我会重命名。对于 rmi.engine
,更喜欢 org.myproject
,以避免与JDK的内部类混淆。
PS: Abstract
is kind of a confusing name. I really thought that you were speaking of abstract class first. I would rename that if possible. Same for rmi.engine
, prefer something like org.myproject
, to avoid confusion with internal class of the JDK.
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