public static void clear() {
        USER_THREAD_LOCAL.remove();
    }
@Test
    public void testClear() {
        UserContext.setUserInfo(USERNAME, USER_ROLE);
        ThreadLocal<UserContext.User> userThreadLocal = (ThreadLocal<UserContext.User>) ReflectUtil.getFieldValue(UserContext.class, "USER_THREAD_LOCAL");
        Assert.notNull(userThreadLocal.get());
        UserContext.clear();
        Assert.isNull(userThreadLocal.get());
    }