黑马程序员Redis课程p37商户查询缓存练习题，详解

首先将ShopTypeController类中的方法修改一下

package com.hmdp.controller;


import com.hmdp.dto.Result;
import com.hmdp.entity.ShopType;
import com.hmdp.service.IShopTypeService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import java.util.List;


@RestController
@RequestMapping("/shop-type")
public class ShopTypeController {
    @Resource
    private IShopTypeService typeService;

//    public Result queryTypeList() {
//        List typeList = typeService
//                .query().orderByAsc("sort").list();
//        return Result.ok(typeList);
//    }

    @GetMapping("list")
    public Result queryTypeList() {
        return typeService.queryTypeLists();
    }
}

IShopTypeService实现类

package com.hmdp.service;

import com.hmdp.dto.Result;
import com.hmdp.entity.ShopType;
import com.baomidou.mybatisplus.extension.service.IService;


public interface IShopTypeService extends IService {

    Result queryTypeLists();
}

ShopTypeServiceImpl实现类

package com.hmdp.service.impl;

import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.ShopType;
import com.hmdp.mapper.ShopTypeMapper;
import com.hmdp.service.IShopTypeService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisConstants;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;


@Service
public class ShopTypeServiceImpl extends ServiceImpl implements IShopTypeService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Override
    public Result queryTypeLists() {
        //获取radis中商户
        String shopType=stringRedisTemplate.opsForValue().get("shopType");
        if (StrUtil.isNotBlank(shopType)) {
            //存在，直接返回
            List shopTypes = JSONUtil.toList(shopType, ShopType.class);
            return Result.ok(shopTypes);
        }
        //不存在，从数据库中查询写入redis
        List shopTypes = query().orderByAsc("sort").list();
        //不存在，返回错误
        if (shopTypes == null) {
            return Result.fail("分类不存在");
        }
        //将查询到的信息存入radis
        stringRedisTemplate.opsForValue().set("shopType",JSONUtil.toJsonStr(shopTypes));
        //返回
        return Result.ok(shopTypes);

    }
}

通过第一次运行，未缓存，获取时间比较长

此时看客户端，shopType已经缓存到redis中

 再次刷新可以看到，时间明显减少，缓存成功