这篇文章主要分享一下项目里遇到的获取request对象为null的问题，具体是在登录的时候触发的邮箱提醒，获取客户端ip地址，然后通过ip地址定位获取定位信息，从而提示账号在哪里登录。

但是登录却发现获取request对象的时候报错了。

 具体的代码如下：这个异常是自己手动抛出的。

package cn.edu.sgu.www.mhxysy.util;

import cn.edu.sgu.www.mhxysy.consts.MimeType;
import cn.edu.sgu.www.mhxysy.exception.GlobalException;
import cn.edu.sgu.www.mhxysy.restful.JsonResult;
import cn.edu.sgu.www.mhxysy.restful.ResponseCode;
import com.alibaba.fastjson.JSON;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * http工具类
 * @author heyunlin
 * @version 1.0
 */
public class HttpUtils {

    /**
     * 获取HttpServletRequest对象
     * @return HttpServletRequest
     */
    public static HttpServletRequest getRequest() {
        RequestAttributes attributes = RequestContextHolder.getRequestAttributes();

        if (attributes != null ) {
            return ((ServletRequestAttributes) attributes).getRequest();
        }

        throw new GlobalException(ResponseCode.ERROR, "获取request对象失败");
    }

}

在项目其他地方也有用这个工具了获取HttpServletRequest对象，都能获取到，觉得很是奇怪。点进去RequestContextHolder这个类的代码里看了一下，好像找到问题了~

这是基于ThreadLocal实现的，所以有了子线程无法访问父线程中设置的数据问题，不知道开发者为什么不用InheritThreadLocal来避免这个问题0v0

于是，把涉及获取request对象ip地址获取的代码放在线程外面，这样就避免了空指针问题了~

package cn.edu.sgu.www.mhxysy.chain.login.impl;

import cn.edu.sgu.www.mhxysy.chain.login.UserLoginHandler;
import cn.edu.sgu.www.mhxysy.config.property.EmailProperties;
import cn.edu.sgu.www.mhxysy.config.property.SystemSettingsProperties;
import cn.edu.sgu.www.mhxysy.entity.location.Location;
import cn.edu.sgu.www.mhxysy.util.EmailUtils;
import cn.edu.sgu.www.mhxysy.util.IpUtils;
import cn.edu.sgu.www.mhxysy.util.LocationUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;

/**
 * @author heyunlin
 * @version 1.0
 */
@Component
public class EmailSendHandler implements UserLoginHandler {

    private Object params;
    private UserLoginHandler next;

    private final EmailUtils emailUtils;
    private final EmailProperties emailProperties;
    private final SystemSettingsProperties systemSettingsProperties;

    @Autowired
    public EmailSendHandler(
            EmailUtils emailUtils,
            EmailProperties emailProperties,
            SystemSettingsProperties systemSettingsProperties) {
        this.emailUtils = emailUtils;
        this.emailProperties = emailProperties;
        this.systemSettingsProperties = systemSettingsProperties;
    }

    @Override
    public void handle() {
        if (emailProperties.isEnable()) {
            String ip = IpUtils.getIp();
            String username = (String) params;
            String zoneId = systemSettingsProperties.getZoneId();
            // 定义日期格式
            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss");

            new Thread(() -> {
                try {
                    String address = "广东广州";
                    Location location = LocationUtils.getLocation(ip);

                    if (systemSettingsProperties.isUseRealLocation()) {
                        String locationAddress = location.getAddress();

                        if (locationAddress != null) {
                            address = locationAddress;
                        }
                    }

                    String text = "您的账号" + username + "在" + address + "登录了。" +
                            "[" + LocalDateTime.now(ZoneId.of(zoneId)).format(formatter) + "]";

                    emailUtils.sendMessage(text);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }).start();
        }

        if (next != null) {
            next.handle();
        }
    }

    @Override
    public void setNext(UserLoginHandler next) {
        this.next = next;
    }

    @Override
    public void setParams(Object params) {
        this.params = params;
    }

}

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总结：遇到这类问题，就把获取request对象的代码放在主线程中，避免因为ThreadLocal的缺陷导致程序异常。

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好了，文章就分享到这里了，看完如果对你有所帮助，不要忘了点赞+收藏哦~