场景一
Service方法抛出的异常不是RuntimeException或者Error类型,并且@Transactional注解上没有指定回滚异常类型。如下
@Service
public class UserServiceImpl implements UserService {
private final UserMapper userMapper;
public UserServiceImpl(UserMapper userMapper) {
this.userMapper = userMapper;
}
@Transactional
@Override
public void saveUser(User user) throws Exception {
userMapper.save(user);
// 测试事务回滚
if (!StringUtils.hasText(user.getUsername())) {
throw new Exception("username不能为空");
}
}
}
这冲情况下,Spring并不会进行事务回滚操作。
默认情况下,Spring事务只对RuntimeException或者Error类型异常(错误)进行回滚,检查异常(通常为业务类异常)不会导致事务回滚。
所以要解决上面这个事务不生效的问题,我们主要有以下两种方式:
手动在@Transactional注解上声明回滚的异常类型(方法抛出该异常及其所有子类型异常都能触发事务回滚):
@Service
public class UserServiceImpl implements UserService {
private final UserMapper userMapper;
public UserServiceImpl(UserMapper userMapper) {
this.userMapper = userMapper;
}
@Transactional(rollbackFor = Exception.class)
@Override
public void saveUser(User user) throws Exception {
userMapper.save(user);
// 测试事务回滚
if (!StringUtils.hasText(user.getUsername())) {
throw new Exception("username不能为空");
}
}
}
2,方法内手动抛出的检查异常类型改为RuntimeException子类型:
定义一个自定义异常类型ParamInvalidException:
public class ParamInvalidException extends RuntimeException{
public ParamInvalidException(String message) {
super(message);
}
}
修改UserServiceImpl的saveUser方法:
@Service
public class UserServiceImpl implements UserService {
private final UserMapper userMapper;
public UserServiceImpl(UserMapper userMapper) {
this.userMapper = userMapper;
}
@Transactional
@Override
public void saveUser(User user) {
userMapper.save(user);
// 测试事务回滚
if (!StringUtils.hasText(user.getUsername())) {
throw new ParamInvalidException("username不能为空");
}
}
}
场景二
非事务方法直接通过this调用本类事务方法。这种情况也是比较常见的,举个例子,修改UserServiceImpl:
@Service
public class UserServiceImpl implements UserService {
private final UserMapper userMapper;
public UserServiceImpl(UserMapper userMapper) {
this.userMapper = userMapper;
}
@Override
public void saveUserTest(User user) {
this.saveUser(user);
}
@Transactional
@Override
public void saveUser(User user) {
userMapper.save(user);
// 测试事务回滚
if (!StringUtils.hasText(user.getUsername())) {
throw new ParamInvalidException("username不能为空");
}
}
}
在UserServiceImpl中,我们新增了saveUserTest方法,该方法没有使用@Transactional注解标注,为非事务方法,内部直接调用了saveUser事务方法。
在入口类里测试该方法的调用:
@EnableTransactionManagement
@SpringBootApplication
public class TransactionApplication {
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(TransactionApplication.class, args);
UserService userService = context.getBean(UserService.class);
User user = new User("2", null, "28");
userService.saveUserTest(user);
}
}
失效的原因为:Spring事务控制使用AOP代理实现,通过对目标对象的代理来增强目标方法。而上面例子直接通过this调用本类的方法的时候,this的指向并非代理类,而是该类本身。
这种情况下要让事务生效主要有如下两种解决方式(原理都是使用代理对象来替代this):
- 从IOC容器中获取UserService Bean,然后调用它的saveUser方法:
@Service
public class UserServiceImpl implements UserService, ApplicationContextAware {
private final UserMapper userMapper;
private ApplicationContext context;
public UserServiceImpl(UserMapper userMapper) {
this.userMapper = userMapper;
}
@Override
public void saveUserTest(User user) {
UserService userService = context.getBean(UserService.class);
userService.saveUser(user);
}
@Transactional
@Override
public void saveUser(User user) {
userMapper.save(user);
// 测试事务回滚
if (!StringUtils.hasText(user.getUsername())) {
throw new ParamInvalidException("username不能为空");
}
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.context = applicationContext;
}
}
上面代码我们通过实现ApplicationContextAware接口注入了应用上下文ApplicationContext,然后从中取出UserService Bean来代替this。
a 从AOP上下文中取出当前代理对象
这种情况首先需要引入AOP Starter:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
b 然后在SpringBoot入口类中通过注解@EnableAspectJAutoProxy(exposeProxy = true)将当前代理对象暴露到AOP上下文中(通过AopContext的ThreadLocal实现)。
最后在UserServcieImpl的saveUserTest方法中通过AopContext获取UserServce的代理对象:
@Service
public class UserServiceImpl implements UserService {
private final UserMapper userMapper;
public UserServiceImpl(UserMapper userMapper) {
this.userMapper = userMapper;
}
@Override
public void saveUserTest(User user) {
UserService userService = (UserService) AopContext.currentProxy();
userService.saveUser(user);
}
@Transactional
@Override
public void saveUser(User user) {
userMapper.save(user);
// 测试事务回滚
if (!StringUtils.hasText(user.getUsername())) {
throw new ParamInvalidException("username不能为空");
}
}
}