bbeaudreault commented on code in PR #5488: URL: https://github.com/apache/hbase/pull/5488#discussion_r1383374974
########## hbase-common/src/main/java/org/apache/hadoop/hbase/util/ReflectedFunctionCache.java: ########## @@ -0,0 +1,121 @@ +/* + * 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 java.io.IOException; +import java.lang.reflect.Modifier; +import java.util.Collections; +import java.util.HashMap; +import java.util.Map; +import java.util.Set; +import java.util.function.Function; +import java.util.stream.Collectors; +import org.apache.yetus.audience.InterfaceAudience; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import org.apache.hbase.thirdparty.com.google.common.reflect.ClassPath; + +/** + * Cache to hold resolved Functions generated through reflection. These can be costly to create, but + * then are much faster than typical Method.invoke calls when executing. Upon construction, finds + * all subclasses in the same package of the passed baseClass. For each found class, creates a + * lambda using + * {@link ReflectionUtils#getOneArgStaticMethodAsFunction(Class, String, Class, Class)}. These are + * added to a hashmap for fast lookup by name later. + * @param <I> the input argument type for the resolved functions + * @param <R> the return type for the resolved functions + */ +@InterfaceAudience.Private +final public class ReflectedFunctionCache<I, R> { + + private static final Logger LOG = LoggerFactory.getLogger(ReflectedFunctionCache.class); + + private final Map<String, Function<I, ? extends R>> lambdasByClass; + + private ReflectedFunctionCache(Map<String, Function<I, ? extends R>> lambdasByClass) { + this.lambdasByClass = lambdasByClass; + } + + /** + * Create a cache of reflected functions using the provided classloader and baseClass. Will find + * all subclasses of the provided baseClass (in the same package), and then foreach look for a + * static one-arg method with the methodName and argClass. The expectation is that the method + * returns a value whose class extends the baseClass. This was primarily designed for use by our + * Filter and Comparator parseFrom methods. + */ + public static <I, R> ReflectedFunctionCache<I, R> create(ClassLoader classLoader, + Class<R> baseClass, Class<I> argClass, String methodName) { + Map<String, Function<I, ? extends R>> lambdasByClass = new HashMap<>(); + Set<? extends Class<? extends R>> classes = getSubclassesInPackage(classLoader, baseClass); + for (Class<? extends R> clazz : classes) { + Function<I, ? extends R> func = createFunction(clazz, methodName, argClass, clazz); + if (func != null) { + lambdasByClass.put(clazz.getName(), func); + } + } + return new ReflectedFunctionCache<>(lambdasByClass); + } + + /** + * 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. + */ + public R getAndCallByName(String className, I argument) { + Function<I, ? extends R> lambda = lambdasByClass.get(className); + + // 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. + if (lambda == null) { + return null; + } + + return lambda.apply(argument); + } + + private static <R> Set<Class<? extends R>> getSubclassesInPackage(ClassLoader classLoader, + Class<R> baseClass) { + try { + return ClassPath.from(classLoader).getAllClasses().stream() Review Comment: It will cause us to load all of the matching ones, i.e. the ones i call `load` on below after filtering to the correct package. So it will load all of the filters in `org.apache.hadoop.hbase.filter` on startup. I thought this was preferable because the number of classes is not large. Since I do it on startup, I don't need to worry about synchronization. I could only populate the cache as Filters are accessed, but then I need to handle synchronization. Would you prefer that? -- This is an automated message from the Apache Git Service. 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