mybatis plus 用法

/        查询年龄小于16
//        QueryWrapper qw = new QueryWrapper();
//        qw.lt("age", 16);
//        userDao.selectList(qw);

        //方式2 lambda
//        QueryWrapper<User> qw = new QueryWrapper<User>();
//        qw.lambda().lt(User::getAge, 18);
//        userDao.selectList(qw);
        //方式3
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
        //10到30岁之间
        lqw.lt(User::getAge, 30).gt(User::getAge, 10);
        //小于10岁或大于30岁
        lqw.lt(User::getAge, 10).or().gt(User::getAge, 30);
        userDao.selectList(lqw);

 

 //查询投影
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
        lqw.select(User::getId, User::getUsername, User::getAge);
        //不使用查询投影
        QueryWrapper<User> lqw = new QueryWrapper<User>();
        lqw.select("id", "username" "age");
    
        //查询总户数
        QueryWrapper<User> lqw = new QueryWrapper<User>();
        lqw.select("count(*) as count");
        List<Map<String, Object>> maps = userDao.selectMaps(lqw);

 

 //= 匹配
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
        lqw.eq(User::getUsername, "jerry").eq(User::getPassword, "jerry");
        User user = userDao.selectOne(lqw);

 

//范围查询
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
        //lt le gt ge between
        lqw.between(User::getAge, 10, 20);
        //模糊匹配
        lqw.like(User::getUsername, "J");
        User user = userDao.selectOne(lqw);

 

 

 

 

 

 

 

 

 

 

 

 

 

设置表前缀

 

不用写TableName

 

 

 

 auto

 表示id自动累加

 

 

  

 使用yml文件配置逻辑删除。就不用实体类中添加TableLogic了

    db-config:
      id-type: assign_id
      table-prefix: tbl_
      logic-delete-field: deleted
      logic-delete-value: 0
      logic-not-delete-value: 1

 

 

应用于2000个请求以下的并发 

第一步，数据库添加一个字段  

第二