springboot手动事物+redis分布式锁保证数据库记录直插入一条(踩坑)

测试user表结构

测试代码（使用mybatis-plus）

import com.ddjava.ddjavademo.dao.UserDao;
import com.ddjava.ddjavademo.entity.User;
import com.ddjava.ddjavademo.utils.lock.RedissLockUtil;
import org.redisson.api.RLock;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.DefaultTransactionDefinition;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;
import java.util.UUID;

/**
 * @Description
 * @Author Wangyw
 * @Date 2021/8/31 1:31 下午
 **/
@RestController
@RequestMapping(value = "/test")
public class TestController {

    @Autowired
    private UserDao userDao;

    @Autowired
    private DataSourceTransactionManager dataSourceTransactionManager;

    /**
     * 测试事物隔离级别+分布式锁
     * 查询user是否存在记录，如果不存在保存一条到数据库,保证数据库只有一条记录
     * 1.查询user是否存在，如果不存在， 抢锁
     * 2.抢到锁再次查询是否库里user是否存在，如果不存再进行创建，
     * 3.提交事物
     * 4.释放锁
     */
    @RequestMapping(value = "/sw")
    public void sw(){
        String lockKey = "aaa";
        RLock lock = null;
        DefaultTransactionDefinition def = new DefaultTransactionDefinition();
        def.setIsolationLevel(TransactionDefinition.ISOLATION_READ_COMMITTED);
        def.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRES_NEW);
        User user = null;
        TransactionStatus transactionStatus = dataSourceTransactionManager.getTransaction(def);
        try {
            List<User> list = userDao.selectList(null);
            if(list != null && list.size() > 0){
                user = list.get(0);
            }
            //TimeUnit.SECONDS.sleep(2);
            if(user == null){
                lock = RedissLockUtil.lock(lockKey);
                System.out.println( "线程 " + Thread.currentThread().getId() + " 拿到锁 " + System.currentTimeMillis());
                list = userDao.selectList(null);
                if(list != null && list.size() > 0){
                    user = list.get(0);
                }
                if(user == null){
                    user = new User();
                    user.setAge(10);
                    user.setName(UUID.randomUUID().toString());
                    user.setAddress(UUID.randomUUID().toString());
                    userDao.insert(user);
                    System.out.println(Thread.currentThread().getName() +  "数据库保存user");
                }else{
                    System.out.println(Thread.currentThread().getName() +  "锁后 partyPlatformUserTrainDataError != null");
                }
            }else{
                System.out.println( "线程 " + Thread.currentThread().getName() + " 查询 user不为空，不需要加锁");
            }
            dataSourceTransactionManager.commit(transactionStatus);
        }catch (Exception e){
            e.printStackTrace();
            dataSourceTransactionManager.rollback(transactionStatus);
        }finally {
            if(lock != null){
                try {
                    lock.unlock();
                    System.out.println( "线程 " + Thread.currentThread().getId() + " 释放锁 " + System.currentTimeMillis());
                }catch (Exception e){
                    System.out.println("释放锁失败");
                    e.printStackTrace();
                }
            }
        }

    }
}

测试结果
发现并不能保证数据库中直插入一条，开启sql日志打印发现在57行代码list = userDao.selectList(null);这行代码执行的sql查询并没有打印，因为mybatis-plus只是对mybatis的增加，mybatis默认是开启了一级缓存，所以虽然spring手动设置了mysql的事物隔离级别，但是56行拿到锁之后执行到57行并没有去查询数据库，而是查询的缓存。

解决方案
关闭一级缓存，

mybatis-plus:
  configuration:
    local-cache-scope: statement