/*
 * Copyright 2002-2006 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.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * TransactionAttribute implementation that works out whether a given
 * exception should cause transaction rollback by applying a number of
 * rollback rules, both positive and negative. If no rules are relevant
 * to the exception, it behaves like DefaultTransactionAttribute
 * (rolling back on runtime exceptions).
 *
 * <p>The TransactionAttributeEditor property editor creates objects
 * of this class.
 *
 * @author Rod Johnson
 * @since 09.04.2003
 * @see TransactionAttributeEditor
 */
public class RuleBasedTransactionAttribute extends DefaultTransactionAttribute {
	
	/** Prefix for rollback-on-exception rules in description strings */
	public static final String PREFIX_ROLLBACK_RULE = "-";

	/** Prefix for commit-on-exception rules in description strings */
	public static final String PREFIX_COMMIT_RULE = "+";


	/** Static for optimal serializability */
	private static final Log logger = LogFactory.getLog(RuleBasedTransactionAttribute.class);

	private List rollbackRules;


	/**
	 * Create a new RuleBasedTransactionAttribute, with default settings.
	 * Can be modified through bean property setters.
	 * @see #setPropagationBehavior
	 * @see #setIsolationLevel
	 * @see #setTimeout
	 * @see #setReadOnly
	 * @see #setName
	 * @see #setRollbackRules
	 */
	public RuleBasedTransactionAttribute() {
		super();
	}

	/**
	 * Copy constructor. Definition can be modified through bean property setters.
	 * @see #setPropagationBehavior
	 * @see #setIsolationLevel
	 * @see #setTimeout
	 * @see #setReadOnly
	 * @see #setName
	 * @see #setRollbackRules
	 */
	public RuleBasedTransactionAttribute(RuleBasedTransactionAttribute other) {
		super(other);
		this.rollbackRules = new ArrayList(other.rollbackRules);
	}

	/**
	 * Create a new DefaultTransactionAttribute with the the given
	 * propagation behavior. Can be modified through bean property setters.
	 * @param propagationBehavior one of the propagation constants in the
	 * TransactionDefinition interface
	 * @param rollbackRules the list of RollbackRuleAttributes to apply
	 * @see #setIsolationLevel
	 * @see #setTimeout
	 * @see #setReadOnly
	 */
	public RuleBasedTransactionAttribute(int propagationBehavior, List rollbackRules) {
		super(propagationBehavior);
		this.rollbackRules = rollbackRules;
	}


	/**
	 * Set the list of <code>RollbackRuleAttribute</code> objects
	 * (and/or <code>NoRollbackRuleAttribute</code> objects) to apply.
	 * @see RollbackRuleAttribute
	 * @see NoRollbackRuleAttribute
	 */
	public void setRollbackRules(List rollbackRules) {
		this.rollbackRules = rollbackRules;
	}

	/**
	 * Return the list of <code>RollbackRuleAttribute</code> objects
	 * (never <code>null</code>).
	 */
	public List getRollbackRules() {
		if (this.rollbackRules == null) {
			this.rollbackRules = new LinkedList();
		}
		return this.rollbackRules;
	}


	/**
	 * Winning rule is the shallowest rule (that is, the closest in the
	 * inheritance hierarchy to the exception). If no rule applies (-1),
	 * return false.
	 * @see TransactionAttribute#rollbackOn(java.lang.Throwable)
	 */
	public boolean rollbackOn(Throwable ex) {
		if (logger.isDebugEnabled()) {
			logger.debug("Applying rules to determine whether transaction should rollback on " + ex);
		}

		RollbackRuleAttribute winner = null;
		int deepest = Integer.MAX_VALUE;

		if (this.rollbackRules != null) {
			for (Iterator it = this.rollbackRules.iterator(); it.hasNext();) {
				RollbackRuleAttribute rule = (RollbackRuleAttribute) it.next();
				int depth = rule.getDepth(ex);
				if (depth >= 0 && depth < deepest) {
					deepest = depth;
					winner = rule;
				}
			}
		}

		if (logger.isDebugEnabled()) {
			logger.debug("Winning rollback rule is: " + winner);
		}

		// User superclass behavior (rollback on unchecked) if no rule matches.
		if (winner == null) {
			logger.debug("No relevant rollback rule found: applying superclass default");
			return super.rollbackOn(ex);
		}
			
		return !(winner instanceof NoRollbackRuleAttribute);
	}


	public String toString() {
		StringBuffer result = getDefinitionDescription();
		if (this.rollbackRules != null) {
			for (Iterator it = this.rollbackRules.iterator(); it.hasNext();) {
				RollbackRuleAttribute rule = (RollbackRuleAttribute) it.next();
				String sign = (rule instanceof NoRollbackRuleAttribute ? PREFIX_COMMIT_RULE : PREFIX_ROLLBACK_RULE);
				result.append(',').append(sign).append(rule.getExceptionName());
			}
		}
		return result.toString();
	}

}

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