| 1 | /* |
| 2 | * Copyright 2006-2007 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package org.springframework.batch.support.transaction; |
| 18 | |
| 19 | import java.util.ArrayList; |
| 20 | import java.util.Collection; |
| 21 | import java.util.HashMap; |
| 22 | import java.util.HashSet; |
| 23 | import java.util.List; |
| 24 | import java.util.Map; |
| 25 | import java.util.Set; |
| 26 | import java.util.concurrent.ConcurrentHashMap; |
| 27 | import java.util.concurrent.ConcurrentMap; |
| 28 | import java.util.concurrent.CopyOnWriteArrayList; |
| 29 | import java.util.concurrent.CopyOnWriteArraySet; |
| 30 | |
| 31 | import org.aopalliance.intercept.MethodInterceptor; |
| 32 | import org.aopalliance.intercept.MethodInvocation; |
| 33 | import org.springframework.aop.framework.ProxyFactory; |
| 34 | import org.springframework.transaction.support.TransactionSynchronization; |
| 35 | import org.springframework.transaction.support.TransactionSynchronizationAdapter; |
| 36 | import org.springframework.transaction.support.TransactionSynchronizationManager; |
| 37 | |
| 38 | /** |
| 39 | * <p> |
| 40 | * Factory for transaction aware objects (like lists, sets, maps). If a |
| 41 | * transaction is active when a method is called on an instance created by the |
| 42 | * factory, it makes a copy of the target object and carries out all operations |
| 43 | * on the copy. Only when the transaction commits is the target re-initialised |
| 44 | * with the copy. |
| 45 | * </p> |
| 46 | * |
| 47 | * <p> |
| 48 | * Works well with collections and maps for testing transactional behaviour |
| 49 | * without needing a database. The base implementation handles lists, sets and |
| 50 | * maps. Subclasses can implement {@link #begin(Object)} and |
| 51 | * {@link #commit(Object, Object)} to provide support for other resources. |
| 52 | * </p> |
| 53 | * |
| 54 | * <p> |
| 55 | * Generally not intended for multi-threaded use, but the |
| 56 | * {@link #createAppendOnlyTransactionalMap() append only version} of |
| 57 | * collections gives isolation between threads operating on different keys in a |
| 58 | * map, provided they only append to the map. (Threads are limited to removing |
| 59 | * entries that were created in the same transaction.) |
| 60 | * </p> |
| 61 | * |
| 62 | * @author Dave Syer |
| 63 | * |
| 64 | */ |
| 65 | public class TransactionAwareProxyFactory<T> { |
| 66 | |
| 67 | private final T target; |
| 68 | |
| 69 | private final boolean appendOnly; |
| 70 | |
| 71 | private TransactionAwareProxyFactory(T target) { |
| 72 | this(target, false); |
| 73 | |
| 74 | } |
| 75 | |
| 76 | private TransactionAwareProxyFactory(T target, boolean appendOnly) { |
| 77 | super(); |
| 78 | this.target = target; |
| 79 | this.appendOnly = appendOnly; |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | * Make a copy of the target that can be used inside a transaction to |
| 84 | * isolate changes from the original. Also called from the factory |
| 85 | * constructor to isolate the target from the original value passed in. |
| 86 | * |
| 87 | * @param target the target object (List, Set or Map) |
| 88 | * @return an independent copy |
| 89 | */ |
| 90 | @SuppressWarnings({ "unchecked", "rawtypes" }) |
| 91 | protected final T begin(T target) { |
| 92 | // Unfortunately in Java 5 this method has to synchronized |
| 93 | // (works OK without in Java 6). |
| 94 | synchronized (target) { |
| 95 | if (target instanceof List) { |
| 96 | if (appendOnly) { |
| 97 | return (T) new ArrayList(); |
| 98 | } |
| 99 | return (T) new ArrayList((List) target); |
| 100 | } |
| 101 | else if (target instanceof Set) { |
| 102 | if (appendOnly) { |
| 103 | return (T) new HashSet(); |
| 104 | } |
| 105 | return (T) new HashSet((Set) target); |
| 106 | } |
| 107 | else if (target instanceof Map) { |
| 108 | if (appendOnly) { |
| 109 | return (T) new HashMap(); |
| 110 | } |
| 111 | return (T) new HashMap((Map) target); |
| 112 | } |
| 113 | else { |
| 114 | throw new UnsupportedOperationException("Cannot copy target for this type: " + target.getClass()); |
| 115 | } |
| 116 | } |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * Take the working copy state and commit it back to the original target. |
| 121 | * The target then reflects all the changes applied to the copy during a |
| 122 | * transaction. |
| 123 | * |
| 124 | * @param copy the working copy. |
| 125 | * @param target the original target of the factory. |
| 126 | */ |
| 127 | @SuppressWarnings({ "unchecked", "rawtypes" }) |
| 128 | protected void commit(T copy, T target) { |
| 129 | // Unfortunately in Java 5 this method has to be synchronized |
| 130 | // (works OK without in Java 6). |
| 131 | synchronized (target) { |
| 132 | if (target instanceof Collection) { |
| 133 | if (!appendOnly) { |
| 134 | ((Collection) target).clear(); |
| 135 | } |
| 136 | ((Collection) target).addAll((Collection) copy); |
| 137 | } |
| 138 | else { |
| 139 | if (!appendOnly) { |
| 140 | ((Map) target).clear(); |
| 141 | } |
| 142 | ((Map) target).putAll((Map) copy); |
| 143 | } |
| 144 | } |
| 145 | } |
| 146 | |
| 147 | private T createInstance() { |
| 148 | |
| 149 | synchronized (target) { |
| 150 | |
| 151 | ProxyFactory factory = new ProxyFactory(target); |
| 152 | factory.addAdvice(new TransactionAwareInterceptor()); |
| 153 | @SuppressWarnings("unchecked") |
| 154 | T instance = (T) factory.getProxy(); |
| 155 | return instance; |
| 156 | |
| 157 | } |
| 158 | |
| 159 | } |
| 160 | |
| 161 | public static <K, V> Map<K, V> createTransactionalMap() { |
| 162 | return (Map<K, V>) new TransactionAwareProxyFactory<ConcurrentHashMap<K, V>>(new ConcurrentHashMap<K, V>()).createInstance(); |
| 163 | } |
| 164 | |
| 165 | public static <K, V> Map<K, V> createTransactionalMap(Map<K, V> map) { |
| 166 | return (Map<K, V>) new TransactionAwareProxyFactory<ConcurrentHashMap<K, V>>(new ConcurrentHashMap<K, V>(map)).createInstance(); |
| 167 | } |
| 168 | |
| 169 | public static <K, V> ConcurrentMap<K, V> createAppendOnlyTransactionalMap() { |
| 170 | return new TransactionAwareProxyFactory<ConcurrentHashMap<K, V>>(new ConcurrentHashMap<K, V>(), true).createInstance(); |
| 171 | } |
| 172 | |
| 173 | public static <T> Set<T> createAppendOnlyTransactionalSet() { |
| 174 | return (Set<T>) new TransactionAwareProxyFactory<CopyOnWriteArraySet<T>>(new CopyOnWriteArraySet<T>(), true).createInstance(); |
| 175 | } |
| 176 | |
| 177 | public static <T> Set<T> createTransactionalSet() { |
| 178 | return (Set<T>) new TransactionAwareProxyFactory<CopyOnWriteArraySet<T>>(new CopyOnWriteArraySet<T>()).createInstance(); |
| 179 | } |
| 180 | |
| 181 | public static <T> Set<T> createTransactionalSet(Set<T> set) { |
| 182 | return (Set<T>) new TransactionAwareProxyFactory<CopyOnWriteArraySet<T>>(new CopyOnWriteArraySet<T>(set)).createInstance(); |
| 183 | } |
| 184 | |
| 185 | public static <T> List<T> createAppendOnlyTransactionalList() { |
| 186 | return (List<T>) new TransactionAwareProxyFactory<CopyOnWriteArrayList<T>>(new CopyOnWriteArrayList<T>(), true).createInstance(); |
| 187 | } |
| 188 | |
| 189 | public static <T> List<T> createTransactionalList() { |
| 190 | return (List<T>) new TransactionAwareProxyFactory<CopyOnWriteArrayList<T>>(new CopyOnWriteArrayList<T>()).createInstance(); |
| 191 | } |
| 192 | |
| 193 | public static <T> List<T> createTransactionalList(List<T> list) { |
| 194 | return (List<T>) new TransactionAwareProxyFactory<CopyOnWriteArrayList<T>>(new CopyOnWriteArrayList<T>(list)).createInstance(); |
| 195 | } |
| 196 | |
| 197 | private class TargetSynchronization extends TransactionSynchronizationAdapter { |
| 198 | |
| 199 | private final T cache; |
| 200 | |
| 201 | private final Object key; |
| 202 | |
| 203 | public TargetSynchronization(Object key, T cache) { |
| 204 | super(); |
| 205 | this.cache = cache; |
| 206 | this.key = key; |
| 207 | } |
| 208 | |
| 209 | public void afterCompletion(int status) { |
| 210 | super.afterCompletion(status); |
| 211 | if (status == TransactionSynchronization.STATUS_COMMITTED) { |
| 212 | synchronized (target) { |
| 213 | commit(cache, target); |
| 214 | } |
| 215 | } |
| 216 | TransactionSynchronizationManager.unbindResource(key); |
| 217 | } |
| 218 | } |
| 219 | |
| 220 | private class TransactionAwareInterceptor implements MethodInterceptor { |
| 221 | |
| 222 | public Object invoke(MethodInvocation invocation) throws Throwable { |
| 223 | |
| 224 | if (!TransactionSynchronizationManager.isActualTransactionActive()) { |
| 225 | return invocation.proceed(); |
| 226 | } |
| 227 | |
| 228 | T cache; |
| 229 | |
| 230 | if (!TransactionSynchronizationManager.hasResource(this)) { |
| 231 | cache = begin(target); |
| 232 | TransactionSynchronizationManager.bindResource(this, cache); |
| 233 | TransactionSynchronizationManager.registerSynchronization(new TargetSynchronization(this, cache)); |
| 234 | } |
| 235 | else { |
| 236 | @SuppressWarnings("unchecked") |
| 237 | T retrievedCache = (T) TransactionSynchronizationManager.getResource(this); |
| 238 | cache = retrievedCache; |
| 239 | } |
| 240 | |
| 241 | Object result = invocation.getMethod().invoke(cache, invocation.getArguments()); |
| 242 | |
| 243 | if (appendOnly) { |
| 244 | String methodName = invocation.getMethod().getName(); |
| 245 | if ((result == null && methodName.equals("get")) |
| 246 | || (Boolean.FALSE.equals(result) && (methodName.startsWith("contains")) || (Boolean.TRUE |
| 247 | .equals(result) && methodName.startsWith("isEmpty")))) { |
| 248 | // In appendOnly mode the result of a get might not be |
| 249 | // in the cache... |
| 250 | return invocation.proceed(); |
| 251 | } |
| 252 | if (result instanceof Collection<?>) { |
| 253 | HashSet<Object> set = new HashSet<Object>((Collection<?>) result); |
| 254 | set.addAll((Collection<?>) invocation.proceed()); |
| 255 | result = set; |
| 256 | } |
| 257 | } |
| 258 | |
| 259 | return result; |
| 260 | |
| 261 | } |
| 262 | } |
| 263 | |
| 264 | } |