Spring中七种事务传播行为：
-
REQUIRED：
使用当前的事务，如果当前没有事务，则自己新建一个事务，子方法是必须运行在一个事务中的；
如果当前存在事务，则加入这个事务，成为一个整体
- 举例：领导有饭吃，我有钱，我会自己买了自己吃；领导有的吃，会分给你一起吃。
-
SUPPORTS：
如果当前有事务，则使用事务；如果当前没有事务，则不适用事务
- 举例：领导没饭吃，我也没饭吃；领导有饭吃，我也有饭吃。
-
MANDATORY：
该传播属性强制必须存在一个事务，如果不存在，则抛出异常
- 举例：领导必须管饭，不管饭没饭吃，我就不干了（抛出异常）
-
REQUIRES_NEW：
如果当前有事务，则挂起该事务，并且自己创建一个新的事务给自己使用；
如果当前没有事务，则同REQUIRED
-
NOT_SUPPORTED：
如果当前有事务，则把事务挂起，自己不使用事务去运行数据库操作
- 举例：领导有饭吃，分一点给你，我太忙了，放一边，我不吃
-
NEVER：
如果当前有事务存在，则抛出异常
- 举例：领导有饭给你吃，我不想吃，我热爱工作，我抛出异常
-
NESTED：
如果当前有事务，则开启子事务（嵌套事务），嵌套事务是独立提交或者回滚；
如果当前没有事务，则同REQUIRED。
但是如果主事务提交，则会携带子事务一起提交。
如果主事务回滚，则子事务会一起回滚。
相反，子事务异常，则父事务可以回滚或不回滚
- 举例： 领导决策不对，老板怪罪，领导带着小弟一同受罪。小弟出了差错，领导可以推卸责任或一起承担责任
源码中的注释
/*
* Copyright 2002-2019 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
*
* https://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.annotation;
import org.springframework.transaction.TransactionDefinition;
/**
* Enumeration that represents transaction propagation behaviors for use
* with the {@link Transactional} annotation, corresponding to the
* {@link TransactionDefinition} interface.
*
* @author Colin Sampaleanu
* @author Juergen Hoeller
* @since 1.2
*/
public enum Propagation {
/**
* Support a current transaction, create a new one if none exists.
* Analogous to EJB transaction attribute of the same name.
* <p>This is the default setting of a transaction annotation.
*/
REQUIRED(TransactionDefinition.PROPAGATION_REQUIRED),
/**
* Support a current transaction, execute non-transactionally if none exists.
* Analogous to EJB transaction attribute of the same name.
* <p>Note: For transaction managers with transaction synchronization,
* {@code SUPPORTS} is slightly different from no transaction at all,
* as it defines a transaction scope that synchronization will apply for.
* As a consequence, the same resources (JDBC Connection, Hibernate Session, etc)
* will be shared for the entire specified scope. Note that this depends on
* the actual synchronization configuration of the transaction manager.
* @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setTransactionSynchronization
*/
SUPPORTS(TransactionDefinition.PROPAGATION_SUPPORTS),
/**
* Support a current transaction, throw an exception if none exists.
* Analogous to EJB transaction attribute of the same name.
*/
MANDATORY(TransactionDefinition.PROPAGATION_MANDATORY),
/**
* Create a new transaction, and suspend the current transaction if one exists.
* Analogous to the EJB transaction attribute of the same name.
* <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box
* on all transaction managers. This in particular applies to
* {@link org.springframework.transaction.jta.JtaTransactionManager},
* which requires the {@code javax.transaction.TransactionManager} to be
* made available to it (which is server-specific in standard Java EE).
* @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager
*/
REQUIRES_NEW(TransactionDefinition.PROPAGATION_REQUIRES_NEW),
/**
* Execute non-transactionally, suspend the current transaction if one exists.
* Analogous to EJB transaction attribute of the same name.
* <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box
* on all transaction managers. This in particular applies to
* {@link org.springframework.transaction.jta.JtaTransactionManager},
* which requires the {@code javax.transaction.TransactionManager} to be
* made available to it (which is server-specific in standard Java EE).
* @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager
*/
NOT_SUPPORTED(TransactionDefinition.PROPAGATION_NOT_SUPPORTED),
/**
* Execute non-transactionally, throw an exception if a transaction exists.
* Analogous to EJB transaction attribute of the same name.
*/
NEVER(TransactionDefinition.PROPAGATION_NEVER),
/**
* Execute within a nested transaction if a current transaction exists,
* behave like {@code REQUIRED} otherwise. There is no analogous feature in EJB.
* <p>Note: Actual creation of a nested transaction will only work on specific
* transaction managers. Out of the box, this only applies to the JDBC
* DataSourceTransactionManager. Some JTA providers might support nested
* transactions as well.
* @see org.springframework.jdbc.datasource.DataSourceTransactionManager
*/
NESTED(TransactionDefinition.PROPAGATION_NESTED);
private final int value;
Propagation(int value) {
this.value = value;
}
public int value() {
return this.value;
}
}
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