org.apache.hadoop.ipc.ProtocolProxy.java Source code

Introduction

Here is the source code for org.apache.hadoop.ipc.ProtocolProxy.java

Source

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.ipc;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.HashSet;

/**
 * a class wraps around a server's proxy, 
 * containing a list of its supported methods.
 * 
 * A list of methods with a value of null indicates that the client and server
 * have the same protocol.
 */
public class ProtocolProxy<T> {
    private Class<T> protocol;
    private T proxy;
    private HashSet<Integer> serverMethods = null;
    final private boolean supportServerMethodCheck;
    private boolean serverMethodsFetched = false;

    /**
     * Constructor
     * 
     * @param protocol protocol class
     * @param proxy its proxy
     * @param supportServerMethodCheck If false proxy will never fetch server
     *        methods and isMethodSupported will always return true. If true,
     *        server methods will be fetched for the first call to 
     *        isMethodSupported. 
     */
    public ProtocolProxy(Class<T> protocol, T proxy, boolean supportServerMethodCheck) {
        this.protocol = protocol;
        this.proxy = proxy;
        this.supportServerMethodCheck = supportServerMethodCheck;
    }

    private void fetchServerMethods(Method method) throws IOException {
        long clientVersion;
        clientVersion = RPC.getProtocolVersion(method.getDeclaringClass());
        int clientMethodsHash = ProtocolSignature.getFingerprint(method.getDeclaringClass().getMethods());
        ProtocolSignature serverInfo = ((VersionedProtocol) proxy)
                .getProtocolSignature(RPC.getProtocolName(protocol), clientVersion, clientMethodsHash);
        long serverVersion = serverInfo.getVersion();
        if (serverVersion != clientVersion) {
            throw new RPC.VersionMismatch(protocol.getName(), clientVersion, serverVersion);
        }
        int[] serverMethodsCodes = serverInfo.getMethods();
        if (serverMethodsCodes != null) {
            serverMethods = new HashSet<Integer>(serverMethodsCodes.length);
            for (int m : serverMethodsCodes) {
                this.serverMethods.add(Integer.valueOf(m));
            }
        }
        serverMethodsFetched = true;
    }

    /*
     * Get the proxy
     */
    public T getProxy() {
        return proxy;
    }

    /**
     * Check if a method is supported by the server or not
     * 
     * @param methodName a method's name in String format
     * @param parameterTypes a method's parameter types
     * @return true if the method is supported by the server
     */
    public synchronized boolean isMethodSupported(String methodName, Class<?>... parameterTypes)
            throws IOException {
        if (!supportServerMethodCheck) {
            return true;
        }
        Method method;
        try {
            method = protocol.getDeclaredMethod(methodName, parameterTypes);
        } catch (SecurityException e) {
            throw new IOException(e);
        } catch (NoSuchMethodException e) {
            throw new IOException(e);
        }
        if (!serverMethodsFetched) {
            fetchServerMethods(method);
        }
        if (serverMethods == null) { // client & server have the same protocol
            return true;
        }
        return serverMethods.contains(Integer.valueOf(ProtocolSignature.getFingerprint(method)));
    }
}