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1. 声明式事务概述

1.1 什么是声明式事务

声明式事务是Spring通过AOP(面向切面编程)实现的事务管理功能。通过@Transactional注解，可以将事务管理代码与业务代码分离，降低代码耦合度。

1.2 基础配置

@Configuration
@EnableTransactionManagement  // 启用事务管理
public class TransactionConfig {// 事务管理器配置已经由Spring Boot自动完成
}

2. @Transactional注解详解

2.1 注解属性说明

@Service
public class TransactionAttributesDemo {@Transactional(// 1. 事务传播行为propagation = Propagation.REQUIRED,  // 默认值// 2. 事务隔离级别isolation = Isolation.READ_COMMITTED,// 3. 事务超时时间(秒)timeout = 30,// 4. 是否只读事务readOnly = false,// 5. 回滚规则rollbackFor = {BusinessException.class},  // 导致回滚的异常类noRollbackFor = {ValidationException.class},  // 不回滚的异常类// 6. 事务管理器transactionManager = "transactionManager")public void businessMethod() {// 业务逻辑}
}

2.2 事务传播行为详解

@Service
@Slf4j
public class TransactionPropagationDemo {@Autowiredprivate UserService userService;// 1. REQUIRED(默认)：支持当前事务，如果不存在则创建新事务@Transactional(propagation = Propagation.REQUIRED)public void required() {// 业务逻辑}// 2. REQUIRES_NEW：创建新事务，挂起当前事务@Transactional(propagation = Propagation.REQUIRES_NEW)public void requiresNew() {// 业务逻辑}// 3. NESTED：如果当前存在事务，则创建嵌套事务@Transactional(propagation = Propagation.NESTED)public void nested() {// 业务逻辑}// 4. SUPPORTS：支持当前事务，如果不存在则以非事务方式执行@Transactional(propagation = Propagation.SUPPORTS)public void supports() {// 业务逻辑}// 5. NOT_SUPPORTED：以非事务方式执行，如果存在事务则挂起@Transactional(propagation = Propagation.NOT_SUPPORTED)public void notSupported() {// 业务逻辑}// 6. MANDATORY：必须在事务中运行，如果不存在事务则抛出异常@Transactional(propagation = Propagation.MANDATORY)public void mandatory() {// 业务逻辑}// 7. NEVER：以非事务方式执行，如果存在事务则抛出异常@Transactional(propagation = Propagation.NEVER)public void never() {// 业务逻辑}
}

2.3 事务隔离级别详解

@Service
public class TransactionIsolationDemo {// 1. READ_UNCOMMITTED：读未提交@Transactional(isolation = Isolation.READ_UNCOMMITTED)public void readUncommitted() {// 可能读取到其他事务未提交的数据（脏读）}// 2. READ_COMMITTED：读已提交@Transactional(isolation = Isolation.READ_COMMITTED)public void readCommitted() {// 只能读取已经提交的数据，但可能出现不可重复读}// 3. REPEATABLE_READ：可重复读@Transactional(isolation = Isolation.REPEATABLE_READ)public void repeatableRead() {// 同一事务内多次读取结果一致，但可能出现幻读}// 4. SERIALIZABLE：串行化@Transactional(isolation = Isolation.SERIALIZABLE)public void serializable() {// 完全串行化执行，性能最差但是最安全}
}

3. 事务失效场景

3.1 常见事务失效情况

@Service
public class TransactionInvalidDemo {// 1. 非public方法@Transactionalprivate void privateMethod() {  // 事务无效// 业务逻辑}// 2. 同类内部调用public void outerMethod() {innerMethod();  // 事务无效}@Transactionalpublic void innerMethod() {// 业务逻辑}// 3. 异常被捕获但未抛出@Transactionalpublic void catchException() {try {// 业务逻辑throw new RuntimeException();} catch (Exception e) {log.error("异常", e);// 异常被吃掉，事务无法回滚}}// 4. 数据库引擎不支持事务(如MySQL的MyISAM)@Transactionalpublic void mysqlEngine() {// 使用不支持事务的表引擎，事务无效}// 5. 异常类型不匹配@Transactional  // 默认只回滚RuntimeExceptionpublic void exceptionType() throws Exception {throw new Exception("检查异常不会回滚");}// 6. 事务传播行为设置错误@Transactional(propagation = Propagation.NEVER)public void wrongPropagation() {// 在已有事务的情况下调用，将抛出异常}// 7. 未被Spring管理class NonSpringBean {@Transactionalpublic void method() {  // 事务无效，因为不是Spring Bean}}// 8. 方法final修饰@Transactionalpublic final void finalMethod() {  // 事务无效，因为final方法无法被代理// 业务逻辑}
}

4. 事务使用最佳实践

4.1 合理设置事务边界

@Service
@Slf4j
public class TransactionBoundaryDemo {@Autowiredprivate UserRepository userRepository;@Autowiredprivate OrderRepository orderRepository;// 错误示例：事务边界太大@Transactionalpublic void wrongBoundary() {// 非事务操作：查询统计long count = userRepository.count();log.info("用户总数: {}", count);// 事务操作：创建订单createOrder();// 非事务操作：发送通知sendNotification();}// 正确示例：精确的事务边界public void rightBoundary() {// 非事务操作long count = userRepository.count();log.info("用户总数: {}", count);// 事务操作createOrderWithTransaction();// 非事务操作sendNotification();}@Transactionalpublic void createOrderWithTransaction() {// 只包含需要事务的操作createOrder();}
}

4.2 正确处理事务异常

@Service
@Slf4j
public class TransactionExceptionDemo {// 1. 定义自定义业务异常public class BusinessException extends RuntimeException {public BusinessException(String message) {super(message);}}// 2. 使用明确的回滚规则@Transactional(rollbackFor = Exception.class)public void handleBusinessException() {try {// 业务逻辑riskyOperation();} catch (BusinessException e) {// 记录业务异常log.error("业务异常", e);throw e;  // 重新抛出确保回滚} catch (Exception e) {// 记录系统异常log.error("系统异常", e);throw new RuntimeException("系统错误", e);}}// 3. 处理特定异常不回滚@Transactional(noRollbackFor = {ValidationException.class})public void handleValidationException() {try {// 业务逻辑validate();} catch (ValidationException e) {// 验证异常，记录但不回滚log.warn("验证失败", e);}}
}

5. 实战示例

5.1 转账业务实现

@Service
@Slf4j
public class TransferService {@Autowiredprivate AccountRepository accountRepository;@Transactional(rollbackFor = Exception.class)public void transfer(String fromAccount, String toAccount, BigDecimal amount) {// 1. 参数校验if (amount.compareTo(BigDecimal.ZERO) <= 0) {throw new IllegalArgumentException("转账金额必须大于0");}// 2. 查询账户Account from = accountRepository.findByAccountNo(fromAccount).orElseThrow(() -> new BusinessException("转出账户不存在"));Account to = accountRepository.findByAccountNo(toAccount).orElseThrow(() -> new BusinessException("转入账户不存在"));// 3. 余额检查if (from.getBalance().compareTo(amount) < 0) {throw new BusinessException("余额不足");}try {// 4. 执行转账from.setBalance(from.getBalance().subtract(amount));to.setBalance(to.getBalance().add(amount));// 5. 保存更改accountRepository.save(from);accountRepository.save(to);// 6. 记录交易日志logTransaction(from, to, amount);} catch (Exception e) {log.error("转账失败", e);throw new BusinessException("转账操作失败");}}private void logTransaction(Account from, Account to, BigDecimal amount) {// 记录交易日志的逻辑}
}

5.2 订单处理实现

@Service
@Slf4j
public class OrderService {@Autowiredprivate OrderRepository orderRepository;@Autowiredprivate PaymentService paymentService;@Autowiredprivate InventoryService inventoryService;@Transactional(rollbackFor = Exception.class)public Order createOrder(OrderRequest request) {// 1. 创建订单Order order = new Order();order.setUserId(request.getUserId());order.setAmount(calculateAmount(request));order.setStatus(OrderStatus.CREATED);// 2. 保存订单order = orderRepository.save(order);try {// 3. 扣减库存（使用REQUIRES_NEW确保独立事务）inventoryService.deductInventory(request.getItems());// 4. 处理支付（使用REQUIRES_NEW确保独立事务）paymentService.processPayment(order);// 5. 更新订单状态order.setStatus(OrderStatus.PAID);order = orderRepository.save(order);return order;} catch (Exception e) {// 6. 异常处理order.setStatus(OrderStatus.FAILED);orderRepository.save(order);throw new BusinessException("订单处理失败", e);}}private BigDecimal calculateAmount(OrderRequest request) {// 计算订单金额的逻辑return BigDecimal.ZERO;}
}