上代码

封装工具类即可在过滤器、拦截器、aop等地方使用（

转发重定向动手试试吧印象更深刻，子线程或线程池需要使用阿里的threadLoacl

）

import java.util.Optional;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import lombok.extern.slf4j.Slf4j;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;


@Slf4j
public class WebUtil {

    private static final String USERID_ATTRIBUTE_NAME = "_user_id";


    public static void setUserId(Integer userId) {
        setAttribute(USERID_ATTRIBUTE_NAME, userId);
    }


    public static Integer getUserId() {
        return Optional.ofNullable((Integer) getAttribute(USERID_ATTRIBUTE_NAME)).orElse(null);
    }

    /**
     * 取
     */
    public static Object getAttribute(String name) {
        return getRequest().getAttribute(name);
    }

    /**
     * 存
     */
    public static void setAttribute(String name, Object val) {
        getRequest().setAttribute(name, val);
    }

    /**
     * 获取 HttpServletRequest
     */
    public static HttpServletRequest getRequest() {
        return ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
                .getRequest();
    }

    /**
     * 获取 HttpServletResponse
     */
    public static HttpServletResponse getResponse() {
        return ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
                .getResponse();
    }


}

源码

可以看到ServletRequestAttributes对象就在ThreadLocal中，无需自己处理生命周期

而HttpServletRequest可已从ServletRequestAttributes中获取

public abstract class RequestContextHolder {
	private static final ThreadLocal<RequestAttributes> requestAttributesHolder = new NamedThreadLocal("Request attributes");
    private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder = new NamedInheritableThreadLocal("Request context");
    
	public static void resetRequestAttributes() {
        requestAttributesHolder.remove();
        inheritableRequestAttributesHolder.remove();
    }
    
	@Nullable
    public static RequestAttributes getRequestAttributes() {
        RequestAttributes attributes = (RequestAttributes)requestAttributesHolder.get();
        if (attributes == null) {
            attributes = (RequestAttributes)inheritableRequestAttributesHolder.get();
        }

        return attributes;
    }
}

而我们的需要的东西就保存在这里了，一个ConcurrentHashMap

public class Request implements HttpServletRequest {
	private final Map<String, Object> attributes = new ConcurrentHashMap<>();
}