import sun.rmi.transport.DGCAckHandler; //导入依赖的package包/类
/**
 * handleMessages decodes transport operations and handles messages
 * appropriately.  If an exception occurs during message handling,
 * the socket is closed.
 */
void handleMessages(Connection conn, boolean persistent) {
    int port = getEndpoint().getPort();

    try {
        DataInputStream in = new DataInputStream(conn.getInputStream());
        do {
            int op = in.read();     // transport op
            if (op == -1) {
                if (tcpLog.isLoggable(Log.BRIEF)) {
                    tcpLog.log(Log.BRIEF, "(port " +
                        port + ") connection closed");
                }
                break;
            }

            if (tcpLog.isLoggable(Log.BRIEF)) {
                tcpLog.log(Log.BRIEF, "(port " + port +
                    ") op = " + op);
            }

            switch (op) {
            case TransportConstants.Call:
                // service incoming RMI call
                RemoteCall call = new StreamRemoteCall(conn);
                if (serviceCall(call) == false)
                    return;
                break;

            case TransportConstants.Ping:
                // send ack for ping
                DataOutputStream out =
                    new DataOutputStream(conn.getOutputStream());
                out.writeByte(TransportConstants.PingAck);
                conn.releaseOutputStream();
                break;

            case TransportConstants.DGCAck:
                DGCAckHandler.received(UID.read(in));
                break;

            default:
                throw new IOException("unknown transport op " + op);
            }
        } while (persistent);

    } catch (IOException e) {
        // exception during processing causes connection to close (below)
        if (tcpLog.isLoggable(Log.BRIEF)) {
            tcpLog.log(Log.BRIEF, "(port " + port +
                ") exception: ", e);
        }
    } finally {
        try {
            conn.close();
        } catch (IOException ex) {
            // eat exception
        }
    }
}
 

import sun.rmi.transport.DGCAckHandler; //导入依赖的package包/类
public static void main(String[] args) throws Exception {

        System.setProperty("sun.rmi.dgc.ackTimeout",
                Long.toString(ACK_TIMEOUT));

        /*
         * Set a socket factory that has a hook for shutting down all client
         * output (writes from client-created sockets and new connection
         * attempts).  We then use this hook right before a remote stub gets
         * deserialized, so that the client will not be able to send a DGC
         * dirty call, or a DGC acknowledgment.  Without the DGC ack, we
         * hope that the RMI runtime will still eventually allow the remote
         * object to be garbage collected.
         */
        RMISocketFactory.setSocketFactory(new TestSF());
        System.err.println("test socket factory set");

        Remote impl = new DGCAckFailure();
        ReferenceQueue refQueue = new ReferenceQueue();
        Reference weakRef = new WeakReference(impl, refQueue);
        ReturnRemote stub =
            (ReturnRemote) UnicastRemoteObject.exportObject(impl);
        System.err.println("remote object exported; stub = " + stub);

        try {
            Object wrappedStub = stub.returnRemote();
            System.err.println("invocation returned: " + wrappedStub);

            impl = null;
            stub = null;        // in case 4114579 ever gets fixed
            System.err.println("strong references to impl cleared");

            System.err.println("waiting for weak reference notification:");
            Reference ref = null;
            for (int i = 0; i < 6; i++) {
                System.gc();
                ref = refQueue.remove(TIMEOUT / 5);
                if (ref != null) {
                    break;
                }
            }
            if (ref != weakRef) {
                throw new RuntimeException("TEST FAILED: " +
                    "timed out, remote object not garbage collected");
            }

            // 8046339
            // All DGCAckHandlers must be properly released after timeout
            Thread.sleep(ACK_TIMEOUT + 100);
            try {
                Field field =
                        DGCAckHandler.class.getDeclaredField("idTable");
                field.setAccessible(true);
                Object obj = field.get(null);
                Map<?,?> idTable = (Map<?,?>)obj;

                if (!idTable.isEmpty()) {
                    throw new RuntimeException("TEST FAILED: " +
                            "DGCAckHandler.idTable isn't empty");
                }
            } catch (ReflectiveOperationException roe) {
                throw new RuntimeException(roe);
            }

            System.err.println("TEST PASSED");

        } finally {
            try {
                UnicastRemoteObject.unexportObject((Remote) weakRef.get(),
                                                   true);
            } catch (Exception e) {
            }
        }
    }