org.apache.hadoop.ipc.ProtocolProxy Maven / Gradle / Ivy
/**
* 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 {
private Class protocol;
private T proxy;
private HashSet 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 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(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)));
}
}