解決子線程中獲取不到HttpServletRequest對象的問題

更新時間：2024年07月08日 11:56:14 作者：沐雨橙風ιε

這篇文章主要介紹了解決子線程中獲取不到HttpServletRequest對象的問題,具有很好的參考價值,希望對大家有所幫助,如有錯誤或未考慮完全的地方,望不吝賜教

子線程中獲取不到HttpServletRequest對象

本文主要分享一下項目里遇到的獲取request對象為null的問題，具體是在登錄的時候觸發(fā)的郵箱提醒，獲取客戶端ip地址，然后通過ip地址定位獲取定位信息，從而提示賬號在哪里登錄。

但是登錄卻發(fā)現(xiàn)獲取request對象的時候報錯了。

具體的代碼

如下：這個異常是自己手動拋出的。

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工具類
 * @author heyunlin
 * @version 1.0
 */
public class HttpUtils {
 
    /**
     * 獲取HttpServletRequest對象
     * @return HttpServletRequest
     */
    public static HttpServletRequest getRequest() {
        RequestAttributes attributes = RequestContextHolder.getRequestAttributes();
 
        if (attributes != null ) {
            return ((ServletRequestAttributes) attributes).getRequest();
        }
 
        throw new GlobalException(ResponseCode.ERROR, "獲取request對象失敗");
    }
 
}

在項目其他地方也有用這個工具了獲取HttpServletRequest對象，都能獲取到，覺得很是奇怪。

點進去RequestContextHolder這個類的代碼里看了一下，好像找到問題了~

這是基于ThreadLocal實現(xiàn)的，可能與子線程無法訪問父線程中設置的數(shù)據(jù)的問題有關。

不會ThreadLocal的童鞋，通過下面文章簡單了解一下ThreadLocal
子線程無法訪問父線程中通過ThreadLocal設置的變量

為了驗證自己的猜測，點開RequestContextHolder的源代碼~

public abstract class RequestContextHolder  {    
    private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
			new NamedThreadLocal<>("Request attributes");
 
	private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =
			new NamedInheritableThreadLocal<>("Request context");
 
	/**
	 * 根據(jù)inheritable的值決定通過ThreadLocal或InhertitableThreadLocal保存RequestAttributes對象 
	 */
	public static void setRequestAttributes(@Nullable RequestAttributes attributes, boolean inheritable) {
		if (attributes == null) {
			resetRequestAttributes();
		} else {
			if (inheritable) {
				inheritableRequestAttributesHolder.set(attributes);
 
				requestAttributesHolder.remove();
			} else {
				requestAttributesHolder.set(attributes);
 
				inheritableRequestAttributesHolder.remove();
			}
		}
	}
 
    /**
	 * 通過Ctrl+鼠標點擊，發(fā)現(xiàn)實際調(diào)用的是這個方法
     * 所以默認是通過ThreadLocal保存的變量
	 */
    public static void setRequestAttributes(@Nullable RequestAttributes attributes) {
		setRequestAttributes(attributes, false);
	}
 
    /**
	 * 獲取ThreadLocal中設置的RequestAttributes對象 
	 */
	@Nullable
	public static RequestAttributes getRequestAttributes() {
        // 因為默認是通過ThreadLocal而不是InheritableThreadLocal保存，
        // 在子線程訪問不到在父線程中通過set()方法設置的變量
		RequestAttributes attributes = requestAttributesHolder.get();
 
        // 所以在子線程中，會走這個分支
		if (attributes == null) {
            // 然后從InheritableThreadLocal中獲取RequestAttributes對象
            // 因為調(diào)用上面第一個setRequestAttributes(RequestAttributes, boolean)方法時傳的參數(shù)是false，所以InheritableThreadLocal中沒有設置RequestAttributes對象，因此，這里get()還是null，最后attributes的值為null
			attributes = inheritableRequestAttributesHolder.get();
		}
 
		return attributes;
	}
 
}

于是，把涉及獲取request對象ip地址獲取的代碼放在線程外面，這樣就避免了空指針問題了~

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();
            // 定義日期格式
            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss");
 
            new Thread(() -> {
                try {
                    String address = "廣東廣州";
                    Location location = LocationUtils.getLocation(ip);
 
                    if (systemSettingsProperties.isUseRealLocation()) {
                        String locationAddress = location.getAddress();
 
                        if (locationAddress != null) {
                            address = locationAddress;
                        }
                    }
 
                    String text = "您的賬號" + username + "在" + address + "登錄了。" +
                            "[" + 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;
    }
 
}