java.rmi.UnmarshalException：无法通过服务器提取客户端类

Question

I have an RMI client/server set-up on two machines that works fine in a simple situation when the server doesn't require a client-side defned class. However, when I need to use a class defined on the client side I am unable to have the server unmarshall those classes. I suspect this is an issue with my java.rmi.server.codebase property that I pass in as argument to the client app. I followed Sun's RMI Tutorial trail and I think I have followed the steps exactly except that I don't specify a classpath argument when executing client and server because they execute in the directory right above the root package directory (however I tried that too with no effect).

The exceptions I get when attempting to execute the different client-side combinations described in detail below are all the same:

RmiServer exception: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: java.lang.ClassNotFoundException: test.MyTask at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:353) at sun.rmi.transport.Transport$1.run(Transport.java:177) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:173) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:142) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132) at $Proxy0.execute(Unknown Source) at test.myClient.main(myClient.java:32)

The details are:

My client/server rmi is set up over a home network behind a router. The router is assigned to a static ip address I will call myhostname . Appropriate port-mapping is set-up in the router that points to the right machines.

server, venice, linux ubuntu 9.10, 10.0.1.2
client, naples, mac os x leopard, 10.0.1.4

I startup the server side as follows inside /home/andrews/workspace/epsilon/bin :

1 starting registry on the default port 1099:

venice% rmiregistry &

2 starting web-server on port 2001 pointing to code base for common interfaces:

venice% java webserver/ClassFileServer 2001 /home/andrew/workspace/epsilon/bin

3 starting server app (main class in test/myServer) which registers the server object:

venice% java -Djava.rmi.server.codebase="http://myhostname:2001/" -Djava.security.policy=server.policy -Djava.rmi.server.hostname=myhostname test/myServer &

Now the client side inside /Users/andrews/Development/Java/workspace/epsilon/bin :

1 start a local web server that can server client-side classes to the server (not sure if this is needed, but I added I tried it, and still no success; I have added port-mapping to the router for 2001 to venice , for 2002 to naples )

naples$ java webserver/ClassFileServer 2002 /Users/andrews/Development/Java/workspace/epsilon/bin/

Trying to run the client (note: I don't specify the -cp argument because client executes right above the root package directory):

1 try #1 using an http hostname

naples$ java -Djava.rmi.server.codebase=http://10.0.1.4:2002/ -Djava.security.policy=client.policy test.myClient myhostname

Note 1: the myhostname argument at the end is passed-in to the client so that it resolves to server's rmi hostname.

Note 2: I tried using localhost:2002 instead of 10.0.1.4:2002 too.

Note 3: I tried using myhostname:2002 since myhostname is assigned to the router and I have proper port-mapping set-up, this address should resolve to naples and not venice

2 try #2:

naples$ java -Djava.rmi.server.codebase=file:/Users/andrews/Development/Java/workspace/epsilon/bin/ -Djava.security.policy=client.policy test.myClient myhostname

Note 1: the code base url format is correct, I created a small program to convert current file directory path into a url and used that. using file:///Users... has same effect.

Other notes:

1 my server and client policy files correctly specify the path, as I've tested this setup with good and bad paths, and getting a security exception for bad path

2 this setup works if I don't use client-side defined objects, the client connects correctly to the server and the server executes.

3 when I place the client-side class on the server in the server's classpath, all executes fine.

All help is appreciated.

Answer 1

Do you really need to use RMI? Me and a friend tried it once in school and it was slow, much slower then the simple ObjectOutputStream networking we had been doing earlier.

Answer 2

I strong agree with Chad Okere's said, RMI is really very slow and consuming-resouces. sometimes directly use Sockets maybe is simple and useful chooice, regarding your exception Could you confirm your rmi server work correctly? http://www.javarmi.com/2010/05/java-rmi-error-unmarshalling-arguments/ maybe be can help you