Redis双重检验同步代码块解决缓存击穿

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import bootandredis.demo.mapper.BookMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import redis.clients.jedis.Jedis;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/*在springboot下进行Redis测试
* 浏览器访问127.0.0.1:8080/redis启动测试*/
@Controller
public class condemo {
@Autowired
private BookMapper bookMapper;
@RequestMapping("/redis")
@ResponseBody
public String con01() {
//创建线程实例
Runnable runnable = new Runnable() {
@Override
public void run() {
//调用需要测试的方法
getBooks();
}
};
// 多线程测试缓存穿透，设置启动线程数为25
ExecutorService executorService = Executors.newFixedThreadPool(25);
//利用25个线程循环启动5000次
for (int i = 0; i < 5000; i++)
executorService.submit(runnable);
return "over";
}
public void getBooks() {
//启动Jedis连接Redis
Jedis j = new Jedis("192.168.37.134", 6379);
//验证登录密码
j.auth("123456");
String s = j.get("books");
//双重验证以确保数据库只被查询一次，避免缓存穿透
if (null == s)
synchronized (this) {
s = j.get("books");
if (null == s) {
s = bookMapper.selectAll().toString();
j.set("books", s);
System.out.println("查询数据库");
}else
System.out.println("查询redis");
}
else {
System.out.println("查询redis");
}
}
}