Spring中事务的传播机制

傷城~ 2022-11-14 11:54 120阅读 0赞

Spring的事务其实就是数据库的事务操作，符合ACID标准，也具有标准的事务隔离级别。

# 传统JDBC事务 #

先来看下传统的JDBC事务的用法：

package com.morris.spring.demo;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TraditionJDBCDemo { 
    	public static void main(String[] args) throws SQLException { 
    		String url = "jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull";
    		String username = "root";
    		String password = "root1234";
    
    		Connection connection = DriverManager.getConnection(url, username, password);
    
    		connection.setAutoCommit(false); // 不自动提交
    		try { 
    
    			Statement statement = connection.createStatement();
    
    			statement.execute("insert into t_area(area_name, area_code) values('湖南', '4000')");
    			statement.execute("insert into t_good(good_name, price) values('iphone12', 9999)");
    			connection.commit(); // 提交事务
    		} catch (Exception e) { 
    			e.printStackTrace();
    			connection.rollback(); // 回滚事务
    		}
    	}
    }

# Spring中的事务 #

Spring中的事务只是对JDBC事务进行一些封装与扩展，其底层最终还是会使用到JDBC的这套API。但是Spring事务有自己的特点，也就是事务传播机制。

所谓事务传播机制，也就是在事务在多个方法的调用中是如何传递的，是重新创建事务还是使用父方法的事务？父方法的回滚对子方法的事务是否有影响？这些都是可以通过事务传播机制来决定的。

## 准备工作 ##

### 实体类 ###

Area

package com.morris.spring.entity;
    
    @Data
    public class Area { 
    
    	private Integer id;
    	private String areaName;
    	private Integer areaCode;
    }

Good

package com.morris.spring.entity;
    
    import java.math.BigDecimal;
    
    @Data
    public class Good { 
    
    	private Integer id;
    	private String goodName;
    	private BigDecimal price;
    }

### DAO层 ###

GoodDao

@Component
    public class GoodDao { 
    
    	@Autowired
    	private JdbcTemplate jdbcTemplate;
    
    	public boolean insert(Good good) { 
    		String sql = "insert into t_good(good_name, price) values(?,?)";
    		return jdbcTemplate.update(sql, good.getGoodName(), good.getPrice()) > 0;
    	}
    }

AreaDao

package com.morris.spring.dao;
    
    import com.morris.spring.entity.Area;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.jdbc.core.JdbcTemplate;
    import org.springframework.stereotype.Component;
    
    @Component
    public class AreaDao { 
    
    	@Autowired
    	private JdbcTemplate jdbcTemplate;
    
    	public boolean insert(Area area) { 
    		//jdbcTemplate.
    		String sql = "insert into t_area(area_name, area_code) values(?,?)";
    		return jdbcTemplate.update(sql, area.getAreaName(), area.getAreaCode()) > 0;
    	}
    }

### Service层 ###

AreaService

package com.morris.spring.service;
    
    public interface AreaService { 
    
    	boolean addArea();
    }

AreaServiceImpl

package com.morris.spring.service;
    
    import com.morris.spring.dao.AreaDao;
    import com.morris.spring.entity.Area;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    import org.springframework.transaction.annotation.Transactional;
    
    @Component
    public class AreaServiceImpl implements AreaService { 
    
    	@Autowired
    	private AreaDao areaDao;
    
    	@Transactional
    	@Override
    	public boolean addArea() { 
    		Area area = new Area();
    		area.setAreaCode(518000);
    		area.setAreaName("深圳");
    		return areaDao.insert(area);
    	}
    }

GoodService

package com.morris.spring.service;
    
    public interface GoodService { 
    	boolean addGood();
    }

GoodServiceImpl

package com.morris.spring.service;
    
    import com.morris.spring.dao.GoodDao;
    import com.morris.spring.entity.Good;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    import org.springframework.transaction.annotation.Transactional;
    
    import java.math.BigDecimal;
    
    @Component
    public class GoodServiceImpl implements GoodService { 
    
    	@Autowired
    	private GoodDao goodDao;
    
    	@Transactional
    	@Override
    	public boolean addGood() { 
    		Good good = new Good();
    		good.setGoodName("iphone11");
    		good.setPrice(new BigDecimal("10000"));
    		return goodDao.insert(good);
    	}
    }

TransactionService

package com.morris.spring.service;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    import org.springframework.transaction.annotation.Transactional;
    
    @Component
    public class TransactionService { 
    
    	@Autowired
    	private GoodService goodService;
    
    	@Autowired
    	private AreaService areaService;
    	
    
    	@Transactional
    	public void addGoodAndArea() { 
    		goodService.addGood();
    		areaService.addArea();
    	}
    
    }

### 测试类 ###

TransactionDemo

package com.morris.spring.demo.annotation;
    
    import com.morris.spring.config.JdbcConfig;
    import com.morris.spring.dao.AreaDao;
    import com.morris.spring.dao.GoodDao;
    import com.morris.spring.service.AreaServiceImpl;
    import com.morris.spring.service.GoodServiceImpl;
    import com.morris.spring.service.TransactionService;
    import org.junit.jupiter.api.Test;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    public class TransactionDemo { 
    
    	@Test
    	public void required() { 
    		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
    		applicationContext.register(GoodDao.class);
    		applicationContext.register(AreaDao.class);
    		applicationContext.register(GoodServiceImpl.class);
    		applicationContext.register(AreaServiceImpl.class);
    		applicationContext.register(JdbcConfig.class);
    		applicationContext.register(TransactionService.class);
    		applicationContext.refresh();
    
    		TransactionService transactionService = applicationContext.getBean(TransactionService.class);
    		transactionService.addGoodAndArea();
    	}
    
    }

## 传播机制 ##

具体选项可以参考枚举类org.springframework.transaction.annotation.Propagation。

<table> 
 <thead> 
  <tr> 
   <th>选项</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>REQUIRED</td> 
   <td>默认选项。如果当前没有事务，就新建一个事务，如果已经存在一个事务中，加入到这个事务中。</td> 
  </tr> 
  <tr> 
   <td>SUPPORTS</td> 
   <td>支持当前事务，如果当前没有事务，就以非事务方式执行。</td> 
  </tr> 
  <tr> 
   <td>MANDATORY</td> 
   <td>使用当前的事务，如果当前没有事务，就抛出异常。</td> 
  </tr> 
  <tr> 
   <td>REQUIRES_NEW</td> 
   <td>新建事务，如果当前存在事务，把当前事务挂起。</td> 
  </tr> 
  <tr> 
   <td>NOT_SUPPORTED</td> 
   <td>以非事务方式执行操作，如果当前存在事务，就把当前事务挂起。</td> 
  </tr> 
  <tr> 
   <td>NEVER</td> 
   <td>以非事务方式执行，如果当前存在事务，则抛出异常。</td> 
  </tr> 
  <tr> 
   <td>NESTED</td> 
   <td>如果当前存在事务，则在嵌套事务内执行。如果当前没有事务，则执行与PROPAGATION_REQUIRED类似的操作。</td> 
  </tr> 
 </tbody> 
</table>

### REQUIRED ###

默认选项。如果当前没有事务，就新建一个事务，如果已经存在一个事务中，加入到这个事务中。

配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：REQUIRED
 *  AreaServiceImpl：REQUIRED

运行上面的Demo，运行结果如下：

总结：

*  当外层没有事务的时候，TransactionService.addGoodAndArea()方法执行发现没有事务可用，自己新建事务。
 *  goodService.addGood()和areaService.addArea()执行时发现已有事务，就使用当前事务执行。

### REQUIRES\_NEW ###

新建事务，如果当前存在事务，把当前事务挂起。

配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：REQUIRED
 *  AreaServiceImpl：REQUIRES\_NEW

运行结果如下：

// 创建事务
    DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.TransactionService.addGoodAndArea]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    // 创建连接
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] to manual commit
    DEBUG DataSourceTransactionManager:479 - Participating in existing transaction
     // 在存在的事务中执行
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_good(good_name, price) values(?,?)]
    // 挂起旧的事务并创建新的事务
    DEBUG DataSourceTransactionManager:438 - Suspending current transaction, creating new transaction with name [com.morris.spring.service.AreaServiceImpl.addArea]
    // 创建连接
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@1c33749] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1c33749] to manual commit
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]
    DEBUG DataSourceTransactionManager:749 - Initiating transaction commit
     // 提交事务
    DEBUG DataSourceTransactionManager:327 - Committing JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@1c33749]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1c33749] after transaction
    // 恢复事务
    DEBUG DataSourceTransactionManager:1017 - Resuming suspended transaction after completion of inner transaction
    DEBUG DataSourceTransactionManager:749 - Initiating transaction commit
     // 提交事务
    DEBUG DataSourceTransactionManager:327 - Committing JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] after transaction

总结：areaService.addArea()执行时发现已有事务，就把当前事务挂起，执行完后再恢复。

### SUPPORTS ###

支持当前事务，如果当前没有事务，就以非事务方式执行。

配置如下：

*  TransactionService：SUPPORTS
 *  GoodServiceImpl：REQUIRED
 *  AreaServiceImpl：SUPPORTS

运行结果如下：

// TransactionService.addGoodAndArea以非事务方式运行
    ------addGoodAndArea-------
    // 开启事务
    DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.GoodServiceImpl.addGood]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@1912c99] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1912c99] to manual commit
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_good(good_name, price) values(?,?)]
    DEBUG DataSourceTransactionManager:749 - Initiating transaction commit
     // 提交事务
    DEBUG DataSourceTransactionManager:327 - Committing JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@1912c99]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1912c99] after transaction
    DEBUG DataSourceTransactionManager:1017 - Resuming suspended transaction after completion of inner transaction
    // AreaServiceImpl.addArea以非事务方式运行
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]

总结：当前没有事务，TransactionService.addGoodAndArea()和AreaServiceImpl.addArea()以非事务方式运行。

修改配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：SUPPORTS
 *  AreaServiceImpl：SUPPORTS

运行结果如下：

总结：当前有事务，GoodServiceImpl.addGood()和AreaServiceImpl.addArea()以事务方式运行。

### MANDATORY ###

使用当前的事务，如果当前没有事务，就抛出异常。

配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：MANDATORY
 *  AreaServiceImpl：REQUIRED

运行结果如下：

总结：当前有事务，GoodServiceImpl.addGood()以事务方式运行。

修改配置如下：

*  TransactionService：SUPPORTS
 *  GoodServiceImpl：MANDATORY
 *  AreaServiceImpl：REQUIRED

运行结果如下：

------addGoodAndArea-------
    DEBUG DataSourceTransactionManager:862 - Should roll back transaction but cannot - no transaction available
    
    org.springframework.transaction.IllegalTransactionStateException: No existing transaction found for transaction marked with propagation 'mandatory'
    
    	at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:367)
    	at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:595)
    	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:376)
    	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:118)

总结：当前没有有事务，GoodServiceImpl.addGood()会抛出异常。

### NOT\_SUPPORTED ###

以非事务方式执行操作，如果当前存在事务，就把当前事务挂起。

配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：NOT\_SUPPORTED
 *  AreaServiceImpl：NOT\_SUPPORTED

运行结果如下：

// 开启事务
    DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.TransactionService.addGoodAndArea]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] to manual commit
    ------addGoodAndArea-------
    DEBUG DataSourceTransactionManager:428 - Suspending current transaction
     // 挂起当前事务
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_good(good_name, price) values(?,?)]
    DEBUG DataSourceUtils:115 - Fetching JDBC Connection from DataSource
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:1017 - Resuming suspended transaction after completion of inner transaction
    DEBUG DataSourceTransactionManager:428 - Suspending current transaction
     // 挂起当前事务
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]
    DEBUG DataSourceUtils:115 - Fetching JDBC Connection from DataSource
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:1017 - Resuming suspended transaction after completion of inner transaction
    DEBUG DataSourceTransactionManager:749 - Initiating transaction commit
    DEBUG DataSourceTransactionManager:327 - Committing JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] after transaction

总结：执行GoodServiceImpl.addGood()和AreaServiceImpl.addArea()时当前存在事务，就把当前事务挂起。

### NEVER ###

以非事务方式执行，如果当前存在事务，则抛出异常。

配置如下：

*  TransactionService：NEVER
 *  GoodServiceImpl：NEVER
 *  AreaServiceImpl：NEVER

运行结果如下：

// 没有事务都以非事务方式运行
    ------addGoodAndArea-------
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_good(good_name, price) values(?,?)]
    DEBUG DataSourceUtils:115 - Fetching JDBC Connection from DataSource
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]

总结：当前没有事务都以非事务方式执行。

修改配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：NEVER
 *  AreaServiceImpl：NEVER

运行结果如下：

DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.TransactionService.addGoodAndArea]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] to manual commit
    ------addGoodAndArea-------
    DEBUG DataSourceTransactionManager:842 - Initiating transaction rollback
    DEBUG DataSourceTransactionManager:342 - Rolling back JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] after transaction
    
    org.springframework.transaction.IllegalTransactionStateException: Existing transaction found for transaction marked with propagation 'never'
    
    	at org.springframework.transaction.support.AbstractPlatformTransactionManager.handleExistingTransaction(AbstractPlatformTransactionManager.java:422)
    	at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:357)
    	at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:595)
    	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:376)
    	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:118)

总结：GoodServiceImpl.addGood()执行时存在事务就会抛出异常。

### NESTED ###

如果当前存在事务，则在嵌套事务内执行。如果当前没有事务，则执行与REQUIRED类似的操作。

配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：NESTED
 *  AreaServiceImpl：NESTED

运行结果如下：

DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.TransactionService.addGoodAndArea]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] to manual commit
    ------addGoodAndArea-------
    DEBUG DataSourceTransactionManager:458 - Creating nested transaction with name [com.morris.spring.service.GoodServiceImpl.addGood]
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_good(good_name, price) values(?,?)]
    DEBUG DataSourceTransactionManager:742 - Releasing transaction savepoint
     // 释放回滚点
    DEBUG DataSourceTransactionManager:458 - Creating nested transaction with name [com.morris.spring.service.AreaServiceImpl.addArea]
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]
    DEBUG DataSourceTransactionManager:742 - Releasing transaction savepoint
     // 释放回滚点
    DEBUG DataSourceTransactionManager:749 - Initiating transaction commit
    DEBUG DataSourceTransactionManager:327 - Committing JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] after transaction

如果不抛出异常，使用REQUIRED与NESTED都差不多，区别在于发生异常，下面演示REQUIRED与NESTED发生异常时的区别：

配置如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：REQUIRED
 *  AreaServiceImpl：REQUIRED

com.morris.spring.service.GoodServiceImpl\#addGood中抛出异常：

@Transactional(propagation = Propagation.REQUIRED)
    public boolean addGood() { 
    	Good good = new Good();
    	good.setGoodName("iphone11");
    	good.setPrice(new BigDecimal("10000"));
    	int j = 0;
    	int i = 10 / j;
    	return goodDao.insert(good);
    }

com.morris.spring.service.TransactionService\#addGoodAndArea中捕获异常：

@Transactional(propagation = Propagation.REQUIRED)
    public void addGoodAndArea() { 
    	System.out.println("------addGoodAndArea-------");
    	try { 
    		goodService.addGood();
    	} catch (Exception e) { 
    		e.printStackTrace();
    	}
    	areaService.addArea();
    }

运行结果如下：

DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.TransactionService.addGoodAndArea]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://10.0.4.122:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] to manual commit
    ------addGoodAndArea-------
    DEBUG DataSourceTransactionManager:479 - Participating in existing transaction
    DEBUG DataSourceTransactionManager:851 - Participating transaction failed - marking existing transaction as rollback-only
    DEBUG DataSourceTransactionManager:356 - Setting JDBC transaction [com.mysql.cj.jdbc.ConnectionImpl@2431d0] rollback-only
    java.lang.ArithmeticException: / by zero
    	at com.morris.spring.service.GoodServiceImpl.addGood(GoodServiceImpl.java:25)
    ... ...
    DEBUG DataSourceTransactionManager:479 - Participating in existing transaction
    ... ...
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]
    DEBUG DataSourceTransactionManager:714 - Global transaction is marked as rollback-only but transactional code requested commit
    DEBUG DataSourceTransactionManager:851 - Participating transaction failed - marking existing transaction as rollback-only
    DEBUG DataSourceTransactionManager:356 - Setting JDBC transaction [com.mysql.cj.jdbc.ConnectionImpl@2431d0] rollback-only
    DEBUG DataSourceTransactionManager:714 - Global transaction is marked as rollback-only but transactional code requested commit
    DEBUG DataSourceTransactionManager:842 - Initiating transaction rollback
    DEBUG DataSourceTransactionManager:342 - Rolling back JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] after transaction
    
    org.springframework.transaction.UnexpectedRollbackException: Transaction rolled back because it has been marked as rollback-only
    ... ...

从运行结果可以发现事务全部都回滚了。

将上面的配置修改如下：

*  TransactionService：REQUIRED
 *  GoodServiceImpl：NESTED
 *  AreaServiceImpl：NESTED

运行结果如下：

DEBUG DataSourceTransactionManager:376 - Creating new transaction with name [com.morris.spring.service.TransactionService.addGoodAndArea]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
    DEBUG DriverManagerDataSource:144 - Creating new JDBC DriverManager Connection to [jdbc:mysql://10.0.4.122:3306/test?useUnicode=true&allowMultiQueries=true&characterEncoding=UTF-8&useFastDateParsing=false&zeroDateTimeBehavior=convertToNull]
    DEBUG DataSourceTransactionManager:264 - Acquired Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] for JDBC transaction
    DEBUG DataSourceTransactionManager:282 - Switching JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] to manual commit
    ------addGoodAndArea-------
    DEBUG DataSourceTransactionManager:458 - Creating nested transaction with name [com.morris.spring.service.GoodServiceImpl.addGood]
    DEBUG DataSourceTransactionManager:836 - Rolling back transaction to savepoint
    java.lang.ArithmeticException: / by zero
    	at com.morris.spring.service.GoodServiceImpl.addGood(GoodServiceImpl.java:25)
    ... ...
    DEBUG DataSourceTransactionManager:458 - Creating nested transaction with name [com.morris.spring.service.AreaServiceImpl.addArea]
    DEBUG JdbcTemplate:860 - Executing prepared SQL update
    DEBUG JdbcTemplate:609 - Executing prepared SQL statement [insert into t_area(area_name, area_code) values(?,?)]
    DEBUG DataSourceTransactionManager:742 - Releasing transaction savepoint
    DEBUG DataSourceTransactionManager:749 - Initiating transaction commit
    DEBUG DataSourceTransactionManager:327 - Committing JDBC transaction on Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0]
    DEBUG DataSourceTransactionManager:386 - Releasing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@2431d0] after transaction

从运行结果可以发现goodService.addGood()回滚了（本来就没有提交内容），areaService.addArea()的内容提交了。