关于RMI服务比较有意思的几点

来源：互联网发布：matlab矩阵某两行相加编辑：程序博客网时间：2024/06/18 05:03

当你使用UnicastRemoteObject.export(Remote)发布一个对象时会触发一次FULL GC。

你必须手动管理你发布的Remote对象，意即如果没有别的客户端访问，你发布的对象/服务会被回收，然后你会收到如下的错

“NO SUCH OBJECT IN TABLE.”

package test;import static java.util.concurrent.TimeUnit.MILLISECONDS;import static java.util.concurrent.TimeUnit.SECONDS;import java.rmi.Remote;import java.rmi.RemoteException;import java.rmi.registry.LocateRegistry;import java.rmi.registry.Registry;import java.rmi.server.UnicastRemoteObject;interface RemoteOperations extends Remote {    String remoteOperation() throws RemoteException;}public final class rmi implements RemoteOperations {    private static final String REMOTE_NAME = RemoteOperations.class.getName();    private static final RemoteOperations classVariable = new rmi();    private static boolean holdStrongReference = false;    private static boolean invokeGarbageCollector = true;    private static int delay = 0;    public static void main(final String... args) throws Exception {        for (final String arg : args) {            if ("-gc".equals(arg)) {                invokeGarbageCollector = true;            } else if ("-nogc".equals(arg)) {                invokeGarbageCollector = false;            } else if ("-hold".equals(arg)) {                holdStrongReference = true;            } else if ("-release".equals(arg)) {                holdStrongReference = false;            } else if (arg.startsWith("-delay")) {                delay = Integer.parseInt(arg.substring("-delay".length()));            } else {                System.err.println("usage: javac RMITest.java && java RMITest [-gc] [-nogc] [-hold] [-release] [-delay<seconds>]");                System.exit(1);            }        }        server();        if (invokeGarbageCollector) {            System.gc();        }        if (delay > 0) {            System.out.println("delaying " + delay + " seconds");            final long milliseconds = MILLISECONDS.convert(delay, SECONDS);            Thread.sleep(milliseconds);        }        client();        System.exit(0); // stop RMI server thread    }    @Override    public String remoteOperation() {        return "foo";    }    private static void server() throws Exception {        // This reference is eligible for GC after this method returns        final RemoteOperations methodVariable = new rmi();        final RemoteOperations toBeStubbed = holdStrongReference ? classVariable : methodVariable;        final Remote remote = UnicastRemoteObject.exportObject(toBeStubbed, 0);        final Registry registry = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);        registry.bind(REMOTE_NAME, remote);    }    private static void client() throws Exception {        final Registry registry = LocateRegistry.getRegistry();        final Remote remote = registry.lookup(REMOTE_NAME);        final RemoteOperations stub = RemoteOperations.class.cast(remote);        final String message = stub.remoteOperation();        System.out.println("received: " + message);    }}

http://stackoverflow.com/questions/645208/java-rmi-nosuchobjectexception-no-such-object-in-table

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