学习目标：
提示：学习如何利用Redis实现添加缓存功能解决缓存穿透版
学习产出：
缓存穿透讲解图：
解决方案：
- 采用缓存空对象
- 采用布隆过滤器
解决方案流程图：
1. 准备pom环境
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-pool2</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
<version>5.1.47</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.3</version>
</dependency>
<!--hutool-->
<dependency>
<groupId>cn.hutool</groupId>
<artifactId>hutool-all</artifactId>
<version>5.7.17</version>
</dependency>
2. 配置ThreadLocal和过滤器
public class UserHolder {
private static final ThreadLocal<UserDTO> tl = new ThreadLocal<>();
public static void saveUser(UserDTO user){
tl.set(user);
}
public static UserDTO getUser(){
return tl.get();
}
public static void removeUser(){
tl.remove();
}
}
@Configuration
public class MvcConfig implements WebMvcConfigurer {
@Autowired
private StringRedisTemplate redis;
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new LoginInterceptor()).excludePathPatterns("/user/code","/user/login","/blog/hot","/shop/**","/shop-type/**","/voucher/**").order(2);
registry.addInterceptor(new RefreshTokenInterceptor(redis)).addPathPatterns("/**").order(1);
}
}
---------------------------------------------
@Slf4j
public class LoginInterceptor implements HandlerInterceptor {
//controller执行之前
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//1.判断是否需要拦截ThreadLocal
if (UserHolder.getUser()==null) {
response.setStatus(401);
return false;
}
//7.放行
return true;
}
//渲染后返回给前台数据前
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
//移除用户，避免内存泄露
UserHolder.removeUser();
}
}
---------------------------------------------------
@Slf4j
public class RefreshTokenInterceptor implements HandlerInterceptor {
//这个对象不是由spring管理的所以不能用注解自动注入
private StringRedisTemplate redis;
public RefreshTokenInterceptor(StringRedisTemplate redis) {
this.redis = redis;
}
//controller执行之前
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//1.获取请求头中的token
String token = request.getHeader("authorization");
if (StrUtil.isBlank(token)) {
return true;
}
//2.基于token获取redis中的用户
//通过key取到hash中的map集合数据
Map<Object, Object> userMap = redis.opsForHash().entries("login:token:" + token);
//3.判断用户是否存在
if (userMap.isEmpty()) {
return true;
}
//5.将查询到的hash数据转为userDto对象
UserDTO userDTO = BeanUtil.fillBeanWithMap(userMap, new UserDTO(), false);
//6.存在，保存用户信息到ThreadLocal中
UserHolder.saveUser(userDTO);
//7.刷新token有效期
redis.expire(LOGIN_USER_KEY + token, 30, TimeUnit.MINUTES);
log.info("我是第一个拦截器当前拦截所有请求的用户为，线程为{},{}",UserHolder.getUser(),Thread.currentThread());
//8.放行
return true;
}
3. Controller层：负责接收请求和向下分配文章来源：https://www.toymoban.com/news/detail-633470.html
@RestController
@RequestMapping("/shop")
public class ShopController {
@Resource
public IShopService shopService;
/**
* 根据id查询商铺信息
* @param id 商铺id
* @return 商铺详情数据
*/
@GetMapping("/{id}")
public Result queryShopById(@PathVariable("id") Long id) {
return Result.ok(shopService.queryShopById(id));
}
}
4. Service层：负责业务的处理逻辑文章来源地址https://www.toymoban.com/news/detail-633470.html
@Service
@Slf4j
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
@Resource
private StringRedisTemplate redis;
public Result queryShopById(Long id) {
//1.从Redis查询数据缓存
String shopCache = redis.opsForValue().get("cache:shop:" + id);
//2.判断是否存在 当shopCache为“”时返回false
if (StrUtil.isNotBlank(shopCache)) {
//3.存在，直接返回
Shop shop = JSONUtil.toBean(shopCache, Shop.class);
return Result.ok(shop);
}
//判断命中的是否是空值
if (shopCache!=null) {
return Result.fail(" 店铺信息不存在 ");
}
//4.不存在，根据id查询数据库
Shop shop = getById(id);
if (ObjectUtil.isEmpty(shop)) {
// 解决缓存穿透
redis.opsForValue().set("cache:shop:" + id,"",2,TimeUnit.MINUTES);
//5.不存在，返回错误
return Result.fail("当前商户不存在");
}
//6.存在，写入redis
redis.opsForValue().set("cache:shop:"+id,JSONUtil.toJsonStr(shop));
redis.expire("cache:shop:"+id,30,TimeUnit.MINUTES);
//7.返回
return Result.ok(shop);
}
}
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