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AbstractFallbackTransactionAttributeSource.java
Upload User: jiancairen
Upload Date: 2007-08-27
Package Size: 26458k
Code Size: 7k
Category:
Java Develop
Development Platform:
Java
- /*
- * Copyright 2002-2004 the original author or authors.
- *
- * Licensed 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.springframework.transaction.interceptor;
- import java.lang.reflect.Method;
- import java.util.Collection;
- import java.util.HashMap;
- import java.util.Iterator;
- import java.util.LinkedList;
- import java.util.List;
- import org.apache.commons.logging.Log;
- import org.apache.commons.logging.LogFactory;
- import org.springframework.aop.support.AopUtils;
- import org.springframework.metadata.Attributes;
- /**
- * Abstract implementation of TransactionAttributeSource that caches attributes
- * for methods, and implements fallback policy of 1. most specific method;
- * 2. target class attribute; 3. declaring method; 4. declaring class.
- *
- * <p>Defaults to using class's transaction attribute if none is associated
- * with the target method. Any transaction attribute associated with the
- * target method completely overrides a class transaction attribute.
- *
- * <p>This implementation caches attributes by method after they are first used.
- * If it's ever desirable to allow dynamic changing of transaction attributes
- * (unlikely) caching could be made configurable. Caching is desirable because
- * of the cost of evaluating rollback rules.
- *
- * @author Rod Johnson
- */
- public abstract class AbstractFallbackTransactionAttributeSource implements TransactionAttributeSource {
- protected final Log logger = LogFactory.getLog(getClass());
- /**
- * Canonical value held in cache to indicate no transaction attribute was
- * found for this method, and we don't need to look again
- */
- private final static Object NULL_TX_ATTRIBUTE = new Object();
- /**
- * Cache of TransactionAttributes, keyed by Method and target class
- */
- private HashMap cache = new HashMap();
- /**
- * Return the transaction attribute for this method invocation.
- * Defaults to the class's transaction attribute if no method
- * attribute is found
- * @param method method for the current invocation. Can't be null
- * @param targetClass target class for this invocation. May be null.
- * @return TransactionAttribute for this method, or null if the method is non-transactional
- */
- public final TransactionAttribute getTransactionAttribute(Method method, Class targetClass) {
- // First, see if we have a cached value
- Object cacheKey = cacheKey(method, targetClass);
- Object cached = cache.get(cacheKey);
- if (cached != null) {
- // Value will either be canonical value indicating there is no transaction attribute,
- // or an actual transaction attribute
- if (cached == NULL_TX_ATTRIBUTE) {
- return null;
- }
- else {
- return (TransactionAttribute) cached;
- }
- }
- else {
- // We need to work it out
- TransactionAttribute txAtt = computeTransactionAttribute(method, targetClass);
- // Put it in the cache
- if (txAtt == null) {
- cache.put(cacheKey, NULL_TX_ATTRIBUTE);
- }
- else {
- cache.put(cacheKey, txAtt);
- }
- return txAtt;
- }
- }
- private Object cacheKey(Method method, Class targetClass) {
- // Class may be null, method can't
- return targetClass + "" + System.identityHashCode(method);
- }
- /**
- * Same return as getTransactionAttribute method, but doesn't cache the result.
- * getTransactionAttribute is a caching decorator for this method.
- */
- private TransactionAttribute computeTransactionAttribute(Method method, Class targetClass) {
- // The method may be on an interface, but we need attributes from the target class.
- // The AopUtils class provides a convenience method for this. If the target class
- // is null, the method will be unchanged.
- Method specificMethod = AopUtils.getMostSpecificMethod(method, targetClass);
- // First try is the method in the target class
- TransactionAttribute txAtt = findTransactionAttribute(findAllAttributes(specificMethod));
- if (txAtt != null)
- return txAtt;
- // Second try is the transaction attribute on the target class
- txAtt = findTransactionAttribute(findAllAttributes(specificMethod.getDeclaringClass()));
- if (txAtt != null)
- return txAtt;
- if (specificMethod != method ) {
- // Fallback is to look at the original method
- txAtt = findTransactionAttribute(findAllAttributes(method));
- if (txAtt != null)
- return txAtt;
- // Last fallback is the class of the original method
- return findTransactionAttribute(findAllAttributes(method.getDeclaringClass()));
- }
- return null;
- }
- /**
- * Subclasses should implement this to return all attributes for this method.
- * We need all because of the need to analyze rollback rules.
- * @param m method to retrieve attributes for
- * @return all attributes associated with this method.
- * May return null.
- */
- protected abstract Collection findAllAttributes(Method m);
- /**
- * Subclasses should implement this to return all attributes for this class.
- * @param clazz class to retrieve attributes for
- * @return all attributes associated with this class.
- * May return null.
- */
- protected abstract Collection findAllAttributes(Class clazz);
- /**
- * Return the transaction attribute, given this set of attributes
- * attached to a method or class.
- * Protected rather than private as subclasses may want to customize
- * how this is done: for example, returning a TransactionAttribute
- * affected by the values of other attributes.
- * This implementation takes into account RollbackRuleAttributes, if
- * the TransactionAttribute is a RuleBasedTransactionAttribute.
- * Return null if it's not transactional.
- * @param atts attributes attached to a method or class. May
- * be null, in which case a null TransactionAttribute will be returned.
- * @return TransactionAttribute configured transaction attribute, or null
- * if none was found
- */
- protected TransactionAttribute findTransactionAttribute(Collection atts) {
- if (atts == null) {
- return null;
- }
- TransactionAttribute txAttribute = null;
- // Check there is a transaction attribute
- for (Iterator itr = atts.iterator(); itr.hasNext() && txAttribute == null; ) {
- Object att = itr.next();
- if (att instanceof TransactionAttribute) {
- txAttribute = (TransactionAttribute) att;
- }
- }
- if (txAttribute instanceof RuleBasedTransactionAttribute) {
- RuleBasedTransactionAttribute rbta = (RuleBasedTransactionAttribute) txAttribute;
- // We really want value: bit of a hack.
- List rollbackRules = new LinkedList();
- for (Iterator it = atts.iterator(); it.hasNext(); ) {
- Object att = it.next();
- if (att instanceof RollbackRuleAttribute) {
- if (logger.isDebugEnabled()) {
- logger.debug("Found RollbackRule: " + att);
- }
- rollbackRules.add(att);
- }
- }
- // Repeatedly setting this isn't elegant, but it works.
- rbta.setRollbackRules(rollbackRules);
- }
- return txAttribute;
- }
- }