/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. * * Copyright (c) 1997-2011 Oracle and/or its affiliates. All rights reserved. * * The contents of this file are subject to the terms of either the GNU * General Public License Version 2 only ("GPL") or the Common Development * and Distribution License("CDDL") (collectively, the "License"). You * may not use this file except in compliance with the License. You can * obtain a copy of the License at * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html * or packager/legal/LICENSE.txt. See the License for the specific * language governing permissions and limitations under the License. * * When distributing the software, include this License Header Notice in each * file and include the License file at packager/legal/LICENSE.txt. * * GPL Classpath Exception: * Oracle designates this particular file as subject to the "Classpath" * exception as provided by Oracle in the GPL Version 2 section of the License * file that accompanied this code. * * Modifications: * If applicable, add the following below the License Header, with the fields * enclosed by brackets [] replaced by your own identifying information: * "Portions Copyright [year] [name of copyright owner]" * * Contributor(s): * If you wish your version of this file to be governed by only the CDDL or * only the GPL Version 2, indicate your decision by adding "[Contributor] * elects to include this software in this distribution under the [CDDL or GPL * Version 2] license." If you don't indicate a single choice of license, a * recipient has the option to distribute your version of this file under * either the CDDL, the GPL Version 2 or to extend the choice of license to * its licensees as provided above. However, if you add GPL Version 2 code * and therefore, elected the GPL Version 2 license, then the option applies * only if the new code is made subject to such option by the copyright * holder. */ package com.sun.ejb.containers.util; import java.util.Map; import java.util.HashMap; import java.util.Set; import java.util.HashSet; import java.util.Iterator; import java.lang.reflect.Method; /** * This is an optimized map for resolving java.lang.reflect.Method objects. * Doing a method lookup, even on an unsynchronized Map, can be an * expensive operation, in many cases taking multiple microseconds. * In most situations this overhead is negligible, but it can be noticeable * when performed in the common path of a local ejb invocation, where our * goal is to be as fast as a raw java method call. * * A MethodMap must be created with an existing Map and is immutable after * construction(except for clear()). * It does not support the optional Map operations * put, putAll, and remove. NOTE that these operations could * be implemented but are not necessary at this point since the main use * is for the container's method info, which is invariant after initialization. * * As this is a map for Method objects, null keys are not supported. * This map is unsynchronized. */ public final class MethodMap extends HashMap { // If bucket size is not specified by caller, this is the number // of buckets per method that will be created. private static final int DEFAULT_BUCKET_MULTIPLIER = 20; private int numBuckets_; // Sparse array of method info. Each element represents one method // or is null. Array is hashed by a combination of the // method name's hashcode and its parameter length. See // getBucket() below for more details. // // Note that reference equality is not very useful on Method since // it defines the equals() method and each call to Class.getMethods() // returns new Method instances. private MethodInfo[] methodInfo_; public MethodMap(Map methodMap) { super(methodMap); numBuckets_ = methodMap.size() * DEFAULT_BUCKET_MULTIPLIER; buildLookupTable(methodMap); } public MethodMap(Map methodMap, int numBuckets) { super(methodMap); if( numBuckets <= 0 ) { throw new IllegalArgumentException ("Invalid value of numBuckets = " + numBuckets); } numBuckets_ = numBuckets; buildLookupTable(methodMap); } public Object put(Object key, Object value) { throw new UnsupportedOperationException(); } public void putAll(Map t) { throw new UnsupportedOperationException(); } public Object remove(Object key) { throw new UnsupportedOperationException(); } public Object get(Object key) { if( key instanceof Method ) { Method m = (Method) key; Class[] paramTypes = m.getParameterTypes(); return get(m, paramTypes.length); } return null; } public Object get(Method m, int numParams) { if( methodInfo_ == null ) { return null; } else if( numParams < 0 ) { throw new IllegalStateException ("invalid numParams = " + numParams); } Object value = null; MethodInfo methodInfo = methodInfo_[getBucket(m, numParams)]; if( methodInfo != null) { // Declaring classes must be the same for methods to be equal. if(methodInfo.declaringClass == m.getDeclaringClass()) { value = methodInfo.value; } } return (value != null) ? value : super.get(m); } public void clear() { if( methodInfo_ != null ) { methodInfo_ = null; super.clear(); } } private void buildLookupTable(Map methodMap) { methodInfo_ = new MethodInfo[numBuckets_]; Set methods = methodMap.keySet(); Set occupied = new HashSet(); for(Iterator iter = methods.iterator(); iter.hasNext();) { Object nextObj = iter.next(); Method next = null; if( nextObj == null ) { throw new IllegalStateException("null keys not supported"); } else if( nextObj instanceof Method ) { next = (Method) nextObj; } else { throw new IllegalStateException ("invalid key type = " + nextObj.getClass() + " key must be of type java.lang.reflect.Method"); } int bucket = getBucket(next); if( !occupied.contains(bucket) ) { MethodInfo methodInfo = new MethodInfo(); methodInfo.key = next; methodInfo.value = methodMap.get(next); // cache declaring class so we can avoid the method call // during lookup operation. methodInfo.declaringClass = next.getDeclaringClass(); methodInfo_[bucket] = methodInfo; occupied.add(bucket); } else { // there's a clash for this bucket, so null it out and // defer to backing HashMap for results. methodInfo_[bucket] = null; } } } private final int getBucket(Method m) { // note : getParameterTypes is guaranteed to be 0-length array // (as opposed to null) for a method with no arguments. Class[] paramTypes = m.getParameterTypes(); return getBucket(m, paramTypes.length); } private final int getBucket(Method m, int numParams) { String methodName = m.getName(); // The normal Method.hashCode() method makes 5 method calls // and does not cache the result. Here, we use the method name's // hashCode since String.hashCode() makes 0 method calls *and* caches // the result. The tradeoff is that using only method name will // not account for overloaded methods, so we also add the number of // parameters to the calculation. In many cases, the caller // already knows the number of parameters, so it can be passed in // to the lookup. This gives up some encapsulation for // speed. It will result in better performance because // we can skip the call to m.getClass().getParameterTypes(), // which results in multiple method calls and can involve some // expensive copying depending of the types themselves. // Of course, this still won't account for the case where methods // are overloaded with the same number of parameters but different // types. However, the cache miss penalty should be small enough // in this case that it's a fair tradeoff. Adding anything else // to the hashcode calculation will have too large an impact on the // common case. int hashCode = methodName.hashCode(); // account for negative hashcodes hashCode = (hashCode >= 0) ? hashCode : (hashCode * -1); hashCode = (hashCode > numParams) ? (hashCode - numParams) : (hashCode + numParams); return (hashCode % numBuckets_); } private class MethodInfo { public Class declaringClass; public Method key; public Object value; } }