## 利用ThreadLocal优化获取用户基本信息（2024-3-13）

• ThreadLocal提供线程的局部变量（set和get方法）
• 线程之间互不影响

//测试类
package com.di.bigevent;

import org.junit.jupiter.api.Test;

public class ThreadLocalTest {

    @Test
    public void testThreadLocalSetAndGet(){

        ThreadLocal tl = new ThreadLocal();

        new Thread(()->{
            tl.set("李星云");
            System.out.println(Thread.currentThread().getName()+": "+ tl.get());
        },"蓝色").start();

        new Thread(()->{
            tl.set("袁天罡");
            System.out.println(Thread.currentThread().getName()+": "+ tl.get());
        },"绿色").start();
    }
}

//拦截器类
package com.di.bigevent.interceptors;

import com.di.bigevent.utils.JwtUtil;
import com.di.bigevent.utils.ThreadLocalUtil;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;

import java.util.Map;

@Component
public class LoginInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //令牌验证
        String token = request.getHeader("Authorization");

        try{
            Map<String,Object> claims = JwtUtil.parseToken(token);

            //把业务数据存放到ThreadLocal中
            ThreadLocalUtil.set(claims);
            //放行
            return true;
        }
        catch(Exception e){
            response.setStatus(401);
            //不放行
            return false;
        }
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //清空ThreadLocal中的数据
        ThreadLocalUtil.remove();
    }
}

//Controller
@GetMapping("userInfo")
    public Result<Object> userInfo(/*@RequestHeader(name = "Authorization") String token*/){
        /*Map<String, Object> map = JwtUtil.parseToken(token);
        String username = (String)map.get("username");*/


        Map<String,Object> map = ThreadLocalUtil.get();
        String username = (String) map.get("username");
        User user = userService.findByUserName(username);

        return Result.success(user);
    }

//util
package com.di.bigevent.utils;

/**
 * ThreadLocal 工具类
 */
@SuppressWarnings("all")
public class ThreadLocalUtil {
    //提供ThreadLocal对象,
    private static final ThreadLocal THREAD_LOCAL = new ThreadLocal();

    //根据键获取值
    public static <T> T get(){
        return (T) THREAD_LOCAL.get();
    }
	
    //存储键值对
    public static void set(Object value){
        THREAD_LOCAL.set(value);
    }


    //清除ThreadLocal 防止内存泄漏
    public static void remove(){
        THREAD_LOCAL.remove();
    }
}