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/*
* 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.hbase.util;
import edu.umd.cs.findbugs.annotations.Nullable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Cache to hold resolved Functions of a specific signature, generated through reflection. These can
* be (relatively) costly to create, but then are much faster than typical Method.invoke calls when
* executing. The cache is built-up on demand as calls are made to new classes. The functions are
* cached for the lifetime of the process. If a function cannot be created (security reasons, method
* not found, etc), a fallback function is cached which always returns null. Callers to
* {@link #getAndCallByName(String, Object)} should have handling for null return values.
*
* An instance is created for a specified baseClass (i.e. Filter), argClass (i.e. byte[]), and
* static methodName to call. These are used to resolve a Function which delegates to that static
* method, if it is found.
* @param the input argument type for the resolved functions
* @param the return type for the resolved functions
*/
@InterfaceAudience.Private
public final class ReflectedFunctionCache {
private static final Logger LOG = LoggerFactory.getLogger(ReflectedFunctionCache.class);
private final ConcurrentMap> lambdasByClass =
new ConcurrentHashMap<>();
private final Class baseClass;
private final Class argClass;
private final String methodName;
private final ClassLoader classLoader;
public ReflectedFunctionCache(Class baseClass, Class argClass, String staticMethodName) {
this.classLoader = getClass().getClassLoader();
this.baseClass = baseClass;
this.argClass = argClass;
this.methodName = staticMethodName;
}
/**
* Get and execute the Function for the given className, passing the argument to the function and
* returning the result.
* @param className the full name of the class to lookup
* @param argument the argument to pass to the function, if found.
* @return null if a function is not found for classname, otherwise the result of the function.
*/
@Nullable
public R getAndCallByName(String className, I argument) {
// todo: if we ever make java9+ our lowest supported jdk version, we can
// handle generating these for newly loaded classes from our DynamicClassLoader using
// MethodHandles.privateLookupIn(). For now this is not possible, because we can't easily
// create a privileged lookup in a non-default ClassLoader. So while this cache loads
// over time, it will never load a custom filter from "hbase.dynamic.jars.dir".
Function lambda =
ConcurrentMapUtils.computeIfAbsent(lambdasByClass, className, () -> loadFunction(className));
return lambda.apply(argument);
}
private Function loadFunction(String className) {
long startTime = System.nanoTime();
try {
Class clazz = Class.forName(className, false, classLoader);
if (!baseClass.isAssignableFrom(clazz)) {
LOG.debug("Requested class {} is not assignable to {}, skipping creation of function",
className, baseClass.getName());
return this::notFound;
}
return ReflectionUtils.getOneArgStaticMethodAsFunction(clazz, methodName, argClass,
(Class) clazz);
} catch (Throwable t) {
LOG.debug("Failed to create function for {}", className, t);
return this::notFound;
} finally {
LOG.debug("Populated cache for {} in {}ms", className,
TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime));
}
}
/**
* In order to use computeIfAbsent, we can't store nulls in our cache. So we store a lambda which
* resolves to null. The contract is that getAndCallByName returns null in this case.
*/
private R notFound(I argument) {
return null;
}
}