通过之前的几篇文章我相信您已经搭建好了运行环境，本次的项目实战是依照happylifeplat-tcc-demo项目来演练，也是非常经典的分布式事务场景：支付成功，进行订单状态的更新，扣除用户账户，库存扣减这几个模块来进行tcc分布式事务。话不多说，让我们一起进入体验吧！
- 首先我们找到 PaymentServiceImpl.makePayment 方法，这是tcc分布式事务的发起者
//tcc分布式事务的发起者
@Tcc(confirmMethod = "confirmOrderStatus", cancelMethod = "cancelOrderStatus")
public void makePayment(Order order) {
order.setStatus(OrderStatusEnum.PAYING.getCode());
orderMapper.update(order);
//扣除用户余额 远端的rpc调用
AccountDTO accountDTO = new AccountDTO();
accountDTO.setAmount(order.getTotalAmount());
accountDTO.setUserId(order.getUserId());
accountService.payment(accountDTO);
//进入扣减库存操作 远端的rpc调用
InventoryDTO inventoryDTO = new InventoryDTO();
inventoryDTO.setCount(order.getCount());
inventoryDTO.setProductId(order.getProductId());
inventoryService.decrease(inventoryDTO);
}
//更新订单的confirm方法
public void confirmOrderStatus(Order order) {
order.setStatus(OrderStatusEnum.PAY_SUCCESS.getCode());
orderMapper.update(order);
LOGGER.info("=========进行订单confirm操作完成================");
}
//更新订单的cancel方法
public void cancelOrderStatus(Order order) {
order.setStatus(OrderStatusEnum.PAY_FAIL.getCode());
orderMapper.update(order);
LOGGER.info("=========进行订单cancel操作完成================");
}
makePayment 方法是tcc分布式事务的发起者，它里面有更新订单状态（本地），进行库存扣减（rpc扣减），资金扣减(rpc调用)
confirmOrderStatus 为订单状态confirm方法，cancelOrderStatus 为订单状态cancel方法。
我们重点关注 @Tcc(confirmMethod = "confirmOrderStatus", cancelMethod = "cancelOrderStatus") 这个注解，为什么加了这个注解就有神奇的作用。
@Tcc注解切面
- 我们找到在happylifeplat-tcc-core包中找到
TccTransactionAspect，这里定义@Tcc的切点。
@Aspect
public abstract class TccTransactionAspect {
private TccTransactionInterceptor tccTransactionInterceptor;
public void setTccTransactionInterceptor(TccTransactionInterceptor tccTransactionInterceptor) {
this.tccTransactionInterceptor = tccTransactionInterceptor;
}
@Pointcut("@annotation(com.happylifeplat.tcc.annotation.Tcc)")
public void txTransactionInterceptor() {
}
@Around("txTransactionInterceptor()")
public Object interceptCompensableMethod(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
return tccTransactionInterceptor.interceptor(proceedingJoinPoint);
}
public abstract int getOrder();
}
我们可以知道Spring实现类的方法凡是加了@Tcc注解的，在调用的时候，都会进行 tccTransactionInterceptor.interceptor 调用。
其次我们发现该类是一个抽象类，肯定会有其他类继承它，你猜的没错，对应dubbo用户，他的继承类为:
@Aspect
@Component
public class DubboTccTransactionAspect extends TccTransactionAspect implements Ordered {
@Autowired
public DubboTccTransactionAspect(DubboTccTransactionInterceptor dubboTccTransactionInterceptor) {
super.setTccTransactionInterceptor(dubboTccTransactionInterceptor);
}
@Override
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE;
}
}
- springcloud的用户,它的继承类为:
@Aspect
@Component
public class SpringCloudTxTransactionAspect extends TccTransactionAspect implements Ordered {
@Autowired
public SpringCloudTxTransactionAspect(SpringCloudTxTransactionInterceptor springCloudTxTransactionInterceptor) {
this.setTccTransactionInterceptor(springCloudTxTransactionInterceptor);
}
public void init() {
}
@Override
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE;
}
}
- 我们注意到他们都实现了Spring的Ordered接口，并重写了 getOrder 方法，都返回了 Ordered.HIGHEST_PRECEDENCE 那么可以知道，他是优先级最高的切面。
TccCoordinatorMethodAspect 切面
@Aspect
@Component
public class TccCoordinatorMethodAspect implements Ordered {
private final TccCoordinatorMethodInterceptor tccCoordinatorMethodInterceptor;
@Autowired
public TccCoordinatorMethodAspect(TccCoordinatorMethodInterceptor tccCoordinatorMethodInterceptor) {
this.tccCoordinatorMethodInterceptor = tccCoordinatorMethodInterceptor;
}
@Pointcut("@annotation(com.happylifeplat.tcc.annotation.Tcc)")
public void coordinatorMethod() {
}
@Around("coordinatorMethod()")
public Object interceptCompensableMethod(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
return tccCoordinatorMethodInterceptor.interceptor(proceedingJoinPoint);
}
@Override
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE + 1;
}
}
该切面是第二优先级的切面，意思就是当我们对有@Tcc注解的方法发起调用的时候，首先会进入 TccTransactionAspect 切面，然后再进入 TccCoordinatorMethodAspect 切面。
该切面主要是用来获取@Tcc注解上的元数据，比如confrim方法名称等等。到这里如果大家基本能明白的话，差不多就了解了整个框架原理，现在让我们来跟踪调用吧。
现在我们回过头，我们来调用 PaymentServiceImpl.makePayment 方法
- dubbo用户，我们会进入如下拦截器:
@Component
public class DubboTccTransactionInterceptor implements TccTransactionInterceptor {
private final TccTransactionAspectService tccTransactionAspectService;
@Autowired
public DubboTccTransactionInterceptor(TccTransactionAspectService tccTransactionAspectService) {
this.tccTransactionAspectService = tccTransactionAspectService;
}
@Override
public Object interceptor(ProceedingJoinPoint pjp) throws Throwable {
final String context = RpcContext.getContext().getAttachment(Constant.TCC_TRANSACTION_CONTEXT);
TccTransactionContext tccTransactionContext = null;
if (StringUtils.isNoneBlank(context)) {
tccTransactionContext =
GsonUtils.getInstance().fromJson(context, TccTransactionContext.class);
}
return tccTransactionAspectService.invoke(tccTransactionContext, pjp);
}
}
- 我们继续跟踪 tccTransactionAspectService.invoke(tccTransactionContext, pjp) ,发现通过判断过后，我们会进入 StartTccTransactionHandler.handler 方法,我们已经进入了分布式事务处理的入口了！
/**
* 分布式事务处理接口
*
* @param point point 切点
* @param context 信息
* @return Object
* @throws Throwable 异常
*/
@Override
public Object handler(ProceedingJoinPoint point, TccTransactionContext context) throws Throwable {
Object returnValue;
try {
//开启分布式事务
tccTransactionManager.begin();
try {
//发起调用 执行try方法
returnValue = point.proceed();
} catch (Throwable throwable) {
//异常执行cancel
tccTransactionManager.cancel();
throw throwable;
}
//try成功执行confirm confirm 失败的话，那就只能走本地补偿
tccTransactionManager.confirm();
} finally {
tccTransactionManager.remove();
}
return returnValue;
}
- 我们进行跟进 tccTransactionManager.begin() 方法:
/**
* 该方法为发起方第一次调用
* 也是tcc事务的入口
*/
void begin() {
LogUtil.debug(LOGGER, () -> "开始执行tcc事务！start");
TccTransaction tccTransaction = CURRENT.get();
if (Objects.isNull(tccTransaction)) {
tccTransaction = new TccTransaction();
tccTransaction.setStatus(TccActionEnum.TRYING.getCode());
tccTransaction.setRole(TccRoleEnum.START.getCode());
}
//保存当前事务信息
coordinatorCommand.execute(new CoordinatorAction(CoordinatorActionEnum.SAVE, tccTransaction));
CURRENT.set(tccTransaction);
//设置tcc事务上下文，这个类会传递给远端
TccTransactionContext context = new TccTransactionContext();
context.setAction(TccActionEnum.TRYING.getCode());//设置执行动作为try
context.setTransId(tccTransaction.getTransId());//设置事务id
TransactionContextLocal.getInstance().set(context);
}
这里我们保存了事务信息，并且开启了事务上下文，并把它保存在了ThreadLoacl里面，大家想想这里为什么一定要保存在ThreadLocal里面。
begin方法执行完后，我们回到切面，现在我们来执行 point.proceed()，当执行这一句代码的时候，会进入第二个切面，即进入了 TccCoordinatorMethodInterceptor
public Object interceptor(ProceedingJoinPoint pjp) throws Throwable {
final TccTransaction currentTransaction = tccTransactionManager.getCurrentTransaction();
if (Objects.nonNull(currentTransaction)) {
final TccActionEnum action = TccActionEnum.acquireByCode(currentTransaction.getStatus());
switch (action) {
case TRYING:
registerParticipant(pjp, currentTransaction.getTransId());
break;
case CONFIRMING:
break;
case CANCELING:
break;
}
}
return pjp.proceed(pjp.getArgs());
}
- 这里由于是在try阶段，直接就进入了 registerParticipant 方法
private void registerParticipant(ProceedingJoinPoint point, String transId) throws NoSuchMethodException {
MethodSignature signature = (MethodSignature) point.getSignature();
Method method = signature.getMethod();
Class<?> clazz = point.getTarget().getClass();
Object[] args = point.getArgs();
final Tcc tcc = method.getAnnotation(Tcc.class);
//获取协调方法
String confirmMethodName = tcc.confirmMethod();
/* if (StringUtils.isBlank(confirmMethodName)) {
confirmMethodName = method.getName();
}*/
String cancelMethodName = tcc.cancelMethod();
/* if (StringUtils.isBlank(cancelMethodName)) {
cancelMethodName = method.getName();
}
*/
//设置模式
final TccPatternEnum pattern = tcc.pattern();
tccTransactionManager.getCurrentTransaction().setPattern(pattern.getCode());
TccInvocation confirmInvocation = null;
if (StringUtils.isNoneBlank(confirmMethodName)) {
confirmInvocation = new TccInvocation(clazz,
confirmMethodName, method.getParameterTypes(), args);
}
TccInvocation cancelInvocation = null;
if (StringUtils.isNoneBlank(cancelMethodName)) {
cancelInvocation = new TccInvocation(clazz,
cancelMethodName,
method.getParameterTypes(), args);
}
//封装调用点
final Participant participant = new Participant(
transId,
confirmInvocation,
cancelInvocation);
tccTransactionManager.enlistParticipant(participant);
}
- 这里就获取了 @Tcc(confirmMethod = "confirmOrderStatus", cancelMethod = "cancelOrderStatus")
的信息，并把他封装成了 Participant，存起来，然后真正的调用 PaymentServiceImpl.makePayment 业务方法，在业务方法里面，我们首先执行的是更新订单状态（相信现在你还记得0.0）:
order.setStatus(OrderStatusEnum.PAYING.getCode());
orderMapper.update(order);
- 接下来，我们进行扣除用户余额,注意扣除余额这里是一个rpc方法：
AccountDTO accountDTO = new AccountDTO();
accountDTO.setAmount(order.getTotalAmount());
accountDTO.setUserId(order.getUserId());
accountService.payment(accountDTO)
- 现在我们来关注 accountService.payment(accountDTO) ，这个接口的定义。
dubbo接口:
public interface AccountService {
/**
* 扣款支付
*
* @param accountDTO 参数dto
* @return true
*/
@Tcc
boolean payment(AccountDTO accountDTO);
}
springcloud接口
@FeignClient(value = "account-service", configuration = MyConfiguration.class)
public interface AccountClient {
@PostMapping("/account-service/account/payment")
@Tcc
Boolean payment(@RequestBody AccountDTO accountDO);
}
很明显这里我们都在接口上加了@Tcc注解，我们知道springAop的特性，在接口上加注解，是无法进入切面的，所以我们在这里，要采用rpc框架的某些特性来帮助我们获取到 @Tcc注解信息。 这一步很重要。当我们发起
accountService.payment(accountDTO) 调用的时候:
- dubbo用户，会走dubbo的filter接口,TccTransactionFilter:
private void registerParticipant(Class clazz, String methodName, Object[] arguments, Class... args) throws TccRuntimeException {
try {
Method method = clazz.getDeclaredMethod(methodName, args);
Tcc tcc = method.getAnnotation(Tcc.class);
if (Objects.nonNull(tcc)) {
//获取事务的上下文
final TccTransactionContext tccTransactionContext =
TransactionContextLocal.getInstance().get();
if (Objects.nonNull(tccTransactionContext)) {
//dubbo rpc传参数
RpcContext.getContext()
.setAttachment(Constant.TCC_TRANSACTION_CONTEXT,
GsonUtils.getInstance().toJson(tccTransactionContext));
}
if (Objects.nonNull(tccTransactionContext)) {
if(TccActionEnum.TRYING.getCode()==tccTransactionContext.getAction()){
//获取协调方法
String confirmMethodName = tcc.confirmMethod();
if (StringUtils.isBlank(confirmMethodName)) {
confirmMethodName = method.getName();
}
String cancelMethodName = tcc.cancelMethod();
if (StringUtils.isBlank(cancelMethodName)) {
cancelMethodName = method.getName();
}
//设置模式
final TccPatternEnum pattern = tcc.pattern();
tccTransactionManager.getCurrentTransaction().setPattern(pattern.getCode());
TccInvocation confirmInvocation = new TccInvocation(clazz,
confirmMethodName,
args, arguments);
TccInvocation cancelInvocation = new TccInvocation(clazz,
cancelMethodName,
args, arguments);
//封装调用点
final Participant participant = new Participant(
tccTransactionContext.getTransId(),
confirmInvocation,
cancelInvocation);
tccTransactionManager.enlistParticipant(participant);
}
}
}
} catch (NoSuchMethodException e) {
throw new TccRuntimeException("not fount method " + e.getMessage());
}
}
- springcloud 用户，则会进入 TccFeignHandler ：
public class TccFeignHandler implements InvocationHandler {
/**
* logger
*/
private static final Logger LOGGER = LoggerFactory.getLogger(TccFeignHandler.class);
private Target<?> target;
private Map<Method, MethodHandler> handlers;
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
} else {
final Tcc tcc = method.getAnnotation(Tcc.class);
if (Objects.isNull(tcc)) {
return this.handlers.get(method).invoke(args);
}
final TccTransactionContext tccTransactionContext =
TransactionContextLocal.getInstance().get();
if (Objects.nonNull(tccTransactionContext)) {
final TccTransactionManager tccTransactionManager =
SpringBeanUtils.getInstance().getBean(TccTransactionManager.class);
if (TccActionEnum.TRYING.getCode() == tccTransactionContext.getAction()) {
//获取协调方法
String confirmMethodName = tcc.confirmMethod();
if (StringUtils.isBlank(confirmMethodName)) {
confirmMethodName = method.getName();
}
String cancelMethodName = tcc.cancelMethod();
if (StringUtils.isBlank(cancelMethodName)) {
cancelMethodName = method.getName();
}
//设置模式
final TccPatternEnum pattern = tcc.pattern();
tccTransactionManager.getCurrentTransaction().setPattern(pattern.getCode());
final Class<?> declaringClass = method.getDeclaringClass();
TccInvocation confirmInvocation = new TccInvocation(declaringClass,
confirmMethodName,
method.getParameterTypes(), args);
TccInvocation cancelInvocation = new TccInvocation(declaringClass,
cancelMethodName,
method.getParameterTypes(), args);
//封装调用点
final Participant participant = new Participant(
tccTransactionContext.getTransId(),
confirmInvocation,
cancelInvocation);
tccTransactionManager.enlistParticipant(participant);
}
}
return this.handlers.get(method).invoke(args);
}
}
public void setTarget(Target<?> target) {
this.target = target;
}
public void setHandlers(Map<Method, MethodHandler> handlers) {
this.handlers = handlers;
}
}
