为什么RMI注册表会忽略java.rmi.server.codebase属性 [英] Why RMI registry is ignoring the java.rmi.server.codebase property

问题描述

我正在运行Java RMI的Hello World示例

1)我在一个空文件夹中运行注册表

motta@motta-laptop ~/tmp $ rmiregistry

2)我启动HTTP服务器以在运行时检索类.下载文件夹包含客户端服务器的远程接口

motta@motta-laptop ~/download $ java NanoHTTPD 8080

3)按照Java RMI教程

的建议，我启动服务器并传递java.rmi.server.codebase属性.

motta@motta-laptop ~/server $ java -Djava.rmi.server.codebase="http://localhost:8080" WarehouseServer

RMI注册表未联系HTTP服务器，并引发异常(请参阅问题后的详细​​信息). 但是如果我执行以下操作

1)使用java.rmi.server.codebase属性启动rmi注册表

motta@motta-laptop ~/tmp $ rmiregistry -J-Djava.rmi.server.codebase="http://localhost:8080/"

2)和以前一样启动HTTP服务器

3)没有任何选择地启动服务器

motta@motta-laptop ~/server $ java WarehouseServer

它可以工作，但是为什么呢?似乎，在第一个过程中，RMI注册中心忽略了java.rmi.server.codebase属性

谢谢

================================

我在跑步

java version "1.7.0_21"
Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode)

RMI注册表中的异常

Constructing server implementation...
Binding server implementation to registry...
Exception in thread "main" java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: 
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: 
java.lang.ClassNotFoundException: Warehouse
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:419)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:273)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:251)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:377)
at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)
at WarehouseServer.main(WarehouseServer.java:14)

解决方案

似乎在第一个过程中，RMI注册中心正在忽略 java.rmi.server.codebase属性.

是正确的.原因是，从JDK 7u21开始，java.rmi.server.useCodebaseOnly属性默认情况下为true，而在以前的版本中，默认情况下为false.

当useCodebaseOnly为false时，RMI注册表(和RMI客户端)使用已从服务器传递给它们的代码库.现在，默认值为true，注册表和客户端将忽略服务器的代码库属性.注册表和客户端必须设置自己的代码库属性以匹配服务器的属性，或者(不建议)将useCodebaseOnly设置回false.有关更多详细信息，请参见 JDK 7中的RMI增强功能. >

RMI指南尚未更新以反映此更改.对于那个很抱歉.我将确保它已更新.

I am running a Hello World example for java RMI

1) I run the registry in an empty folder

motta@motta-laptop ~/tmp $ rmiregistry

2) I start the HTTP server to retrieve the classes at runtime. The download folder contains the remote interface for the client-server

motta@motta-laptop ~/download $ java NanoHTTPD 8080

3) I start the server passing the java.rmi.server.codebase property as suggested in the java RMI tutorial

motta@motta-laptop ~/server $ java -Djava.rmi.server.codebase="http://localhost:8080" WarehouseServer

The RMI registry is not contacting the HTTP server and is throwing an exception (see details after the question). But if I do the following

1) Start the rmi registry with the java.rmi.server.codebase property

motta@motta-laptop ~/tmp $ rmiregistry -J-Djava.rmi.server.codebase="http://localhost:8080/"

2) Start the HTTP server as before

3) Start the server without any option

motta@motta-laptop ~/server $ java WarehouseServer

it works, but why? It seems that with the first procedure the RMI registry is ignoring the java.rmi.server.codebase property

Thank you

=================================

I am running

java version "1.7.0_21"
Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode)

The exception from the RMI registry

Constructing server implementation...
Binding server implementation to registry...
Exception in thread "main" java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: 
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: 
java.lang.ClassNotFoundException: Warehouse
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:419)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:273)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:251)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:377)
at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)
at WarehouseServer.main(WarehouseServer.java:14)

解决方案

It seems that with the first procedure the RMI registry is ignoring the java.rmi.server.codebase property.

That's correct. The reason is that, as of JDK 7u21, the java.rmi.server.useCodebaseOnly property is true by default, whereas in prior releases it was false by default.

When useCodebaseOnly is false, the RMI Registry (and RMI clients) use the codebase that has been passed to them from the server. Now that the default value is true the registry and clients ignore the server's codebase property. The registry and clients must either set their own codebase property to match that of the server, or (not recommended) they could set useCodebaseOnly back to false. See RMI Enhancements in JDK 7 for further details.

The RMI Tutorial hasn't been updated to reflect this change. Sorry about that. I'll make sure it gets updated.

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