REDIS02_基于SpringBoot+Mybatis+Redis重写Redis的序列化的缓存实战（三）

@Api(description = "用户User接口")
@RestController
@Slf4j
public class UserController {
    @Resource
    private UserService userService;
    @ApiOperation("数据库新增5条记录")
    @RequestMapping(value = "/user/add",method = RequestMethod.POST)
    public void addUser() {
        for (int i = 1; i <=5; i++) {
            User user = new User();
            user.setId(Integer.parseInt("100"+i));
            user.setUsername("TANGZHI"+i);
            user.setPassword(IdUtil.simpleUUID().substring(0,6));
            user.setSex((byte) new Random().nextInt(2));
            user.setCreateTime(new Date());
            userService.addUser(user);
        }
    }
    @ApiOperation("删除1条记录")
    @RequestMapping(value = "/user/delete/{id}",method = RequestMethod.POST)
    public void deleteUser(@PathVariable Integer id) {
        userService.deleteUser(id);
    }
    @ApiOperation("修改1条记录")
    @RequestMapping(value = "/user/update",method = RequestMethod.POST)
    public void updateUser(@RequestBody UserDTO userDTO) {
        User user = new User();
        BeanUtils.copyProperties(userDTO,user);
        userService.updateUser(user);
    }
    @ApiOperation("查询1条记录")
    @RequestMapping(value = "/user/find/{id}",method = RequestMethod.GET)
    public User findUserById(@PathVariable Integer id) {
        return userService.findUserById(id);
    }
}

@Service
@Slf4j
public class UserService {
    public static final String CACHE_KEY_USER = "user:";
    @Resource
    private UserMapper userMapper;
    @Resource
    private RedisTemplate redisTemplate;
    //新增
    public void addUser(User user) {
        //1 先插入mysql并成功
        int i = userMapper.insertSelective(user);
        if(i > 0) {
            //2 需要再次查询一下mysql将数据捞回来并ok
            user = userMapper.selectByPrimaryKey(user.getId());
            //3 将捞出来的user存进redis,完成新增功能的数据一致性。
            String key = CACHE_KEY_USER+user.getId();
            redisTemplate.opsForValue().set(key,user);
        }
    }
    //刪除
    public void deleteUser(Integer id) {
        int i = userMapper.deleteByPrimaryKey(id);
        if(i > 0) {
            String key = CACHE_KEY_USER+id;
            redisTemplate.delete(key);
        }
    }
    //修改
    public void updateUser(User user) {
        int i = userMapper.updateByPrimaryKeySelective(user);
        if(i > 0) {
            //2 需要再次查询一下mysql将数据捞回来并ok
            user = userMapper.selectByPrimaryKey(user.getId());
            //3 将捞出来的user存进redis,完成修改
            String key = CACHE_KEY_USER+user.getId();
            redisTemplate.opsForValue().set(key,user);
        }
    }
    /**
     * 业务逻辑并没有写错,对于小厂中厂(QPS《=1000)可以使用,但是大厂不行
     * @param id
     * @return
     */
    public User findUserById(Integer id) {
        User user = null;
        String key = CACHE_KEY_USER+id;
        //1 先从redis里面查询,如果有直接1返回结果,如果没有再去查询mysql
        user = (User) redisTemplate.opsForValue().get(key);
        if(user == null) {
            //2 redis里面无,继续查询mysql
            user = userMapper.selectByPrimaryKey(id);
            if(user == null) {
                //3.1 redis+mysql 都无数据
                //你具体细化,防止多次穿透,我们规定,记录下导致穿透的这个key回写redis
                return user;
            }else{
                //3.2 mysql有,需要将数据写回redis,保证下一次的缓存命中率
                redisTemplate.opsForValue().set(key,user);
            }
        }
        return user;
    }
    /**
     * 加强补充,避免突然key实现了,打爆mysql,做一下预防,尽量不出现击穿的情况。
     * @param id
     * @return
     */
    public User findUserById2(Integer id) {
        User user = null;
        String key = CACHE_KEY_USER+id;
        //1 先从redis里面查询,如果有直接返回结果,如果没有再去查询mysql
        user = (User) redisTemplate.opsForValue().get(key);
        if(user == null) {
            //2 大厂用,对于高QPS的优化,进来就先加锁,保证一个请求操作,让外面的redis等待一下,避免击穿mysql
            synchronized (UserService.class){
                user = (User) redisTemplate.opsForValue().get(key);
                //3 二次查redis还是null,可以去查mysql了(mysql默认有数据)
                if (user == null) {
                    //4 查询mysql拿数据
                    user = userMapper.selectByPrimaryKey(id);//mysql有数据默认
                    if (user == null) {
                        return null;
                    }else{
                        //5 mysql里面有数据的,需要回写redis,完成数据一致性的同步工作
                        //setnx 不存在才创建
                        redisTemplate.opsForValue().setIfAbsent(key,user,7L,TimeUnit.DAYS);
                    }
                }
            }
        }
        return user;
    }
}