redis缓存使用本地锁

redis缓存使用本地锁可以解决单体项目缓存击穿问题

在N个相同服务，会存在执行最多N次

 redis缓存使用本地锁代码：

package com.hdb.pingmoweb.product.web;
 
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.TypeReference;
import com.hdb.pingmoweb.product.entity.CategoryEntity;
import com.hdb.pingmoweb.product.service.CategoryService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
 
import java.io.IOException;
import java.util.List;
 
@Controller
public class IndexController {
 
    @Autowired
    private CategoryService categoryService;
 
    @Autowired
    private StringRedisTemplate stringRedisTemplate;
 
    @RequestMapping({"/", "/index"})
    public String index(Model model) throws IOException {
        String level1Category = stringRedisTemplate.opsForValue().get("Level1Category");
        List list = null;
        if (StringUtils.isEmpty(level1Category)) {
            synchronized (this) {
                level1Category = stringRedisTemplate.opsForValue().get("Level1Category");
                if (StringUtils.isEmpty(level1Category)) {
                    System.out.println("查询数据。。。。。。。。。");
                    list = categoryService.getLevel1Category();
                    level1Category = JSON.toJSONString(list);
                    stringRedisTemplate.opsForValue().set("Level1Category", level1Category);
                }
            }
        }
        if(list ==null){
            list = JSON.parseObject(level1Category, new TypeReference>(){});
            System.out.println("缓存命中。。。");
        }
        model.addAttribute("categorys", list);
        return "index";
    }
 
    @ResponseBody
    @RequestMapping("/hello")
    public String hello(Model model) {
        return "hello";
    }
}