一个线上Java空指针问题的排查经过

某天,运营反馈,某商品下单异常

1.原来是一个空指针报错

根据用户输入的下单关键信息搜索日志系统看到如下报错

stackTrace: "java.lang.NullPointerException
	at com.auto.order.service.utils.OrderingUtils.buildParentOrderData(OrderingUtils.java:194)
	at com.auto.order.service.cart.impl.OrderingCommonServiceImpl.handleStat(OrderingCommonServiceImpl.java:1221)
	at com.auto.order.service.cart.impl.OrderingIndexServiceImpl.receive(OrderingIndexServiceImpl.java:1027)
	at com.auto.order.service.impl.OrderApiServiceImpl.receive(OrderApiServiceImpl.java:1979)
	at com.auto.order.site.controller.neworder.OrderingIndexController.receive(OrderingIndexController.java:368)

原来是个空指针错误,来看下194行代码是啥

1 parentOrderData.setRefCookie(orderingReceiveParamBo.getRefCookie());
2 parentOrderData.setCityId(orderingReceiveParamBo.getRuleCityId().intValue());//194行
3 parentOrderData.setSessionId(orderingReceiveParamBo.getSessionId() != null ? orderingReceiveParamBo.getSessionId() : ""); 

上面代码块第二行就是原文件里194行,判断得出应该是ruleCityId字段为空导致了空指针异常;又看了下parentOrderData对象和orderingReceiveParamBo对象的ruleCityId字段都是Integer类型,这里没有必要intValue,改之如下

2 parentOrderData.setCityId(orderingReceiveParamBo.getRuleCityId());//194行

 上线后,以为问题就解决了呢,谁知依旧报错,继续翻看日志,发现如下报错

--- Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'city_id' cannot be null
	at org.springframework.jdbc.support.SQLStateSQLExceptionTranslator.doTranslate(SQLStateSQLExceptionTranslator.java:102)
	at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:73)
	at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:82)
	at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:82)

2.看来不仅仅是一个空指针

数据库里设置了city_id字段是非空的,但是程序没有获取到city_id,为啥获取不到呢,继续排查city_id是怎么获取的

/**
 * 获取所在城市
 */
public static int mallCityId(HttpServletRequest request){
    try {
        String ck = getCookieValue(request.getCookies(), "cookieCityId");
        if ( "999999".equals(ck)) {
            return 110100;
        }
        if (StringUtils.isNotBlank(ck) && Integer.parseInt(ck) > 0) {
            return ck.indexOf("9999") > 0 ? Integer.parseInt(ck.substring(0, 2) + "0100") : Integer.parseInt(ck.substring(0, 4) + "00");
        }
        ck = getCookieValue(request.getCookies(),"area");
        if ("999999".equals(ck)) {
            return 110100;
        }
        if (StringUtils.isNotBlank(ck) && Integer.parseInt(ck) > 0) {
            return ck.indexOf("9999") > 0 ? Integer.parseInt(ck.substring(0, 2) + "0100") : Integer.parseInt(ck.substring(0, 4) + "00");
        }
    } catch (Exception e) {
        indexLog.error("mallCityId is error!",e);
    }
    return 110100;
}

  

代码中city_id是从cookie中获取的,但是这一段代码返回结果不可能为null,即使有异常,也该返回默认城市110100!继续看哪里调用了这个方法,原来是在拦截器方法里调用了这个方法取各种cookie,并做容错处理,主要代码如下

/**
     * 方法执行前的拦截方法
     */
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String sessionId = "";
        Long pvId = 0L;
        Long positionId = 0L;
        Integer cityId = 0;
        String sessionVid = "";
        String refCookie = "";
        String sessionIp="";

        Long s = System.currentTimeMillis();
        try {
            sessionId = getCookieValue(request.getCookies(),"sessionid");
            sessionVid = getCookieValue(request.getCookies(),"sessionvid");
            sessionIp = getCookieValue(request.getCookies(),"sessionip");
            pvId = Long.valueOf(StringUtils.isNotBlank(getCookieValue(request.getCookies(), "mpvareaid")) ? getCookieValue(request.getCookies(), "mpvareaid") : "0");
            positionId = Long.valueOf(StringUtils.isNotBlank(getCookieValue(request.getCookies(), "autohomeareaid")) ? getCookieValue(request.getCookies(), "autohomeareaid") : "0");
            cityId = mallCityId(request);
            request.setAttribute(CUR_SESSION_ID,sessionId);
            request.setAttribute(CUR_SESSION_IP,sessionIp);
            request.setAttribute(CUR_SESSION_VID,(sessionVid == null?"":sessionVid));
            request.setAttribute(CUR_REF_COOKIE,(refCookie == null?"":refCookie));
            request.setAttribute(CUR_PV_ID,pvId);
            request.setAttribute(CUR_POSITION_ID,positionId);
            request.setAttribute(CUR_CITY_ID,cityId);
            request.setAttribute(PARTNER, getCookieValue(request.getCookies(), PARTNER));
            request.setAttribute(CURR_UNIX_TIME, System.currentTimeMillis());
        } catch (Exception e) {
            log.error("get interceptor error:", e);
        }
        timeLog.info("interceptor end   timecost=======>"+(System.currentTimeMillis()-s));
        return true;
    }

  这个拦截器方法,粗看下去没有发现任何问题,如果这个方法有异常,但是日志系统死活没有看到catch打印的error堆栈信息;如果没异常,按流程走下来,cityId字段不可能为空啊!怎么办,笨方法,加日志,我把这个方法调用 mallCityId 方法之上每隔一行都加了日志,看哪行有猫腻

  通过加日志定位到了问题所在,上面代码块的第18行一直走不到,18行就是这个

pvId = Long.valueOf(StringUtils.isNotBlank(getCookieValue(request.getCookies(), "mpvareaid")) ? getCookieValue(request.getCookies(), "mpvareaid") : "0");

  仔细看这一行,真有可能出了问题,如果从cookie里取出来的不是数字,还要 Long.valueOf 肯定就报错了,But为啥捕获不到异常,再看catch块log打印到哪里了

    private static Logger log = LoggerFactory.getLogger(CommonInterceptor.class);
    private static final Logger timeLog = LoggerFactory.getLogger("creat-order-time");
    private static final Logger indexLog = LoggerFactory.getLogger("access-index");

  log对应的是 CommonInterceptor.class ,但是log4j2.xml文件里并没有配置这个类文件,其他两个日志文件在log4j2.xml文件里都有配置,唯独这个CommonInterceptor.class 没有映射,那日志打印到哪里了呢?最后在tomcat的catalina.out文件看到了报错

一个线上Java空指针问题的排查经过_第1张图片

  上图报错行,正好对应的就是拦截器里第18行,从cookie里取出来的mpvareaid是undefined,所以类型转换就报错了,但是由于缺少log4j日志配置,没有在常规业务日志路径捕获到该异常。最后把业务日志路径改了,兼容了undefined情况,问题最终解决

3.总结两点

  第一:未兼容从cookie里取出来的异常数据undefined

  第二:日志打印不规范,没有合理配置日志路径

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