概念

threadlocal为每一个线程提供一个单独的存储空间，具有线程隔离的作用，只有在线程内才能获取到对应的值，线程外则不能访问

工具类

``` public class BaseContext {

public static ThreadLocal threadLocal = new ThreadLocal<>();

public static void setCurrentId(Long id) {
threadLocal.set(id);
}

public static Long getCurrentId() {
return threadLocal.get();
}

public static void removeCurrentId() {
threadLocal.remove();
}

} ```