抛出检查异常导致事务不能正确回滚业务方法内自己 try-catch 异常导致事务不能正确回滚aop 切面顺序导致导致事务不能正确回滚非 public 方法导致的事务失效父子容器导致的事务失效调用本类方法导致传播行为失效@Transactional 没有保证原子行为
@Transactional 方法导致的 synchronized 失效
抛出检查异常导致事务不能正确回滚@Service
public class Service1 {
@Autowired
private AccountMapper accountMapper;
@Transactional
public void transfer(int from, int to, int amount) throws FileNotFoundException {
int fromBalance = accountMapper.findBalanceBy(from);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
new FileInputStream("aaa");
accountMapper.update(to, amount);
}
}
}
原因：Spring 默认只会回滚非检查异常，默认是RuntimeException和Error的子类
解法：配置 rollbackFor 属性
@Transactional(rollbackFor = Exception.class)
业务方法内自己 try-catch 异常导致事务不能正确回滚
@Service
public class Service2 {
@Autowired
private AccountMapper accountMapper;
@Transactional(rollbackFor = Exception.class)
public void transfer(int from, int to, int amount) {
try {
int fromBalance = accountMapper.findBalanceBy(from);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
new FileInputStream("aaa");
accountMapper.update(to, amount);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
原因：事务通知只有捉到了目标抛出的异常，才能进行后续的回滚处理，如果目标自己处理掉异常，事务通知无法知悉
解法1：异常原样抛出
在 catch 块添加 throw new RuntimeException(e);
解法2：手动设置 TransactionStatus.setRollbackonly()
在 catch 块添加 TransactionInterceptor.currentTransactionStatus().setRollbackonly();
aop 切面顺序导致导致事务不能正确回滚@Service
public class Service3 {
@Autowired
private AccountMapper accountMapper;
@Transactional(rollbackFor = Exception.class)
public void transfer(int from, int to, int amount) throws FileNotFoundException {
int fromBalance = accountMapper.findBalanceBy(from);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
new FileInputStream("aaa");
accountMapper.update(to, amount);
}
}
}
@Aspect
public class MyAspect {
@Around("execution(* transfer(..))")
public Object around(ProceedingJoinPoint pjp) throws Throwable {
LoggerUtils.get().debug("log:{}", pjp.getTarget());
try {
return pjp.proceed();
} catch (Throwable e) {
e.printStackTrace();
return null;
}
}
}
原因：事务切面优先级最低，但如果自定义的切面优先级和他一样，则还是自定义切面在内层，这时若自定义切面没有正确抛出异常…
解法1、2：同情况2 中的解法:1、2
解法3：调整切面顺序，在 MyAspect 上添加 @Order(Ordered.LOWEST_PRECEDENCE - 1) （不推荐）
非 public 方法导致的事务失效@Service
public class Service4 {
@Autowired
private AccountMapper accountMapper;
@Transactional
void transfer(int from, int to, int amount) throws FileNotFoundException {
int fromBalance = accountMapper.findBalanceBy(from);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
accountMapper.update(to, amount);
}
}
}
原因：Spring 为方法创建代理、添加事务通知、前提条件都是该方法是 public 的
解法1：改为 public 方法
解法2：添加 bean 配置如下（不推荐）
@Bean
public TransactionAttributeSource transactionAttributeSource() {
return new AnnotationTransactionAttributeSource(false);
}
父子容器导致的事务失效
@Service
public class Service5 {
@Autowired
private AccountMapper accountMapper;
@Transactional(rollbackFor = Exception.class)
public void transfer(int from, int to, int amount) throws FileNotFoundException {
int fromBalance = accountMapper.findBalanceBy(from);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
accountMapper.update(to, amount);
}
}
}
控制器类
@Controller
public class AccountController {
@Autowired
public Service5 service;
public void transfer(int from, int to, int amount) throws FileNotFoundException {
service.transfer(from, to, amount);
}
}
App 配置类
@Configuration
@ComponentScan("com.example.tx.invalid.app.service")
@EnableTransactionManagement
// ...
public class AppConfig {
// ... 有事务相关配置
}
Web 配置类
@Configuration
@ComponentScan("com.example.tx.invalid.app")
// ...
public class WebConfig {
// ... 无事务配置
}
现在配置了父子容器，WebConfig 对应子容器，AppConfig 对应父容器，发现事务依然失效
原因：子容器扫描范围过大，把未加事务配置的 service 扫描进来
解法1：各扫描各的，不要图简便
解法2：不要用父子容器，所有 bean 放在同一容器
调用本类方法导致传播行为失效@Service
public class Service6 {
@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public void foo() throws FileNotFoundException {
LoggerUtils.get().debug("foo");
bar();
}
@Transactional(propagation = Propagation.REQUIRES_NEW, rollbackFor = Exception.class)
public void bar() throws FileNotFoundException {
LoggerUtils.get().debug("bar");
}
}
原因：本类方法调用不经过代理，因此无法增强
解法1：依赖注入自己（代理）来调用
解法2：通过 AopContext 拿到代理对象，来调用
解法3：通过 CTW，LTW 实现功能增强
解法1
@Service
public class Service6 {
@Autowired
private Service6 proxy; // 本质上是一种循环依赖
@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public void foo() throws FileNotFoundException {
LoggerUtils.get().debug("foo");
System.out.println(proxy.getClass());
proxy.bar();
}
@Transactional(propagation = Propagation.REQUIRES_NEW, rollbackFor = Exception.class)
public void bar() throws FileNotFoundException {
LoggerUtils.get().debug("bar");
}
}
解法2，还需要在 AppConfig 上添加 @EnableAspectJAutoProxy(exposeProxy = true)
@Service
public class Service6 {
@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public void foo() throws FileNotFoundException {
LoggerUtils.get().debug("foo");
((Service6) AopContext.currentProxy()).bar();
}
@Transactional(propagation = Propagation.REQUIRES_NEW, rollbackFor = Exception.class)
public void bar() throws FileNotFoundException {
LoggerUtils.get().debug("bar");
}
}
@Transactional 没有保证原子行为
@Service
public class Service7 {
private static final Logger logger = LoggerFactory.getLogger(Service7.class);
@Autowired
private AccountMapper accountMapper;
@Transactional(rollbackFor = Exception.class)
public void transfer(int from, int to, int amount) {
int fromBalance = accountMapper.findBalanceBy(from);
logger.debug("更新前查询余额为: {}", fromBalance);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
accountMapper.update(to, amount);
}
}
public int findBalance(int accountNo) {
return accountMapper.findBalanceBy(accountNo);
}
}
上面的代码实际上是有 bug 的，假设 from 余额为 1000，两个线程都来转账 1000，可能会出现扣减为负数的情况
原因：事务的原子性仅涵盖 insert、update、delete、select … for update 语句，select 方法并不阻塞
如上图所示，红色线程和蓝色线程的查询都发生在扣减之前，都以为自己有足够的余额做扣减 @Transactional 方法导致的 synchronized 失效
针对上面的问题，能否在方法上加 synchronized 锁来解决呢？
@Service
public class Service7 {
private static final Logger logger = LoggerFactory.getLogger(Service7.class);
@Autowired
private AccountMapper accountMapper;
@Transactional(rollbackFor = Exception.class)
public synchronized void transfer(int from, int to, int amount) {
int fromBalance = accountMapper.findBalanceBy(from);
logger.debug("更新前查询余额为: {}", fromBalance);
if (fromBalance - amount >= 0) {
accountMapper.update(from, -1 * amount);
accountMapper.update(to, amount);
}
}
public int findBalance(int accountNo) {
return accountMapper.findBalanceBy(accountNo);
}
}
答案是不行，原因如下：
synchronized 保证的仅是目标方法的原子性，环绕目标方法的还有 commit 等操作，它们并未处于 sync 块内可以参考下图发现，蓝色线程的查询只要在红色线程提交之前执行，那么依然会查询到有 1000 足够余额来转账解法1：synchronized 范围应扩大至代理方法调用
解法2：使用 select … for update 替换 select
本文测试代码地址： https://github.com/fafeidou/fast-summary
