在mybatis拦截器实现双写并且支持处理事务的方法（使用TransactionalEventListener实现）

书接上文：不使用binlog,canal,kafka等，只用java+mybatis拦截器来实现项目中的异步双写主从数据库，代码逻辑全整理
我目前在双写的项目发现中还差一个缺陷，就是如果有事务注解的情况下，发生了回滚，我的异步双写成功写入，但是主库插入失败，这里就用到了TransactionalEventListener作为参考来实现异步双写的事务回滚
参考如下：TransactionalEventListener使用场景以及实现原理，最后要躲个大坑

然后再我的拦截器中应用，新加package如下

TrxEvent继承ApplicationEvent类，作为传参我自定义了几个字段

public class TrxEvent extends ApplicationEvent {
    private String tableName;
    private Object obj;

    private Map param;
    private String sqlCommandType;

    private String isObjOrMap;

    public TrxEvent(Object source) {
        super(source);
    }

    public String getTableName() {
        return tableName;
    }

    public void setTableName(String tableName) {
        this.tableName = tableName;
    }

    public Object getObj() {
        return obj;
    }

    public void setObj(Object obj) {
        this.obj = obj;
    }

    public Map getParam() {
        return param;
    }

    public void setParam(Map param) {
        this.param = param;
    }

    public String getSqlCommandType() {
        return sqlCommandType;
    }

    public void setSqlCommandType(String sqlCommandType) {
        this.sqlCommandType = sqlCommandType;
    }

    public String getIsObjOrMap() {
        return isObjOrMap;
    }

    public void setIsObjOrMap(String isObjOrMap) {
        this.isObjOrMap = isObjOrMap;
    }
}

其中构造需要实现如下

  public TrxEvent(Object source) {
        super(source);
    }

然后是监听器UserCreatedEventListener，注入我的双写service和ApplicationEventPublisher做发布事件操作

@Component
public class UserCreatedEventListener {

    @Autowired
    private DoubleWriteService doubleWriteService;

    @Autowired
    private ApplicationEventPublisher applicationEventPublisher;

    public UserCreatedEventListener(DoubleWriteService doubleWriteService) {
        this.doubleWriteService = doubleWriteService;
    }

    @TransactionalEventListener(fallbackExecution = true, phase = TransactionPhase.AFTER_COMMIT)
    public void processUserCreatedEvent(TrxEvent event) {
        if (event.getIsObjOrMap().equals("obj")){
            if (DoubleWriteConstants.UPDATE.equals(event.getSqlCommandType())){
                doubleWriteService.update(event.getTableName(),event.getObj());
            }else if (DoubleWriteConstants.INSERT.equals(event.getSqlCommandType())){
                doubleWriteService.insert(event.getTableName(), event.getObj());
            }
        }else if (event.getIsObjOrMap().equals("map")){
            if (DoubleWriteConstants.UPDATE.equals(event.getSqlCommandType())){
                doubleWriteService.update(event.getTableName(),event.getParam());
            }else if (DoubleWriteConstants.INSERT.equals(event.getSqlCommandType())){
                doubleWriteService.insert(event.getTableName(), event.getParam());
            }
        }


    }


    public void publish(String isObjOrMap, String sqlCommandType, Map param,Object obj,String tableName){
        TrxEvent event = new TrxEvent(this);
        event.setIsObjOrMap(isObjOrMap);
        event.setTableName(tableName);
        event.setObj(obj);
        event.setParam(param);
        event.setSqlCommandType(sqlCommandType);
        applicationEventPublisher.publishEvent(event);
    }
}

关键注解如下，一定要设置事务阶段是AFTER_COMMIT提交后才执行

最后去mybatis拦截器里，调用发布事件

最后调试截图就不贴了，基本都能保证事务成功提交后，从库开始写入。否则失败回滚后，直接从库不执行写入操作