首頁(yè) 猿問(wèn) 這個(gè)問(wèn)題太奇怪了，已經(jīng)抓狂了

這個(gè)問(wèn)題太奇怪了，已經(jīng)抓狂了

Java

慕斯王 2019-04-19 18:15:22

2014-8-14 13:43:43 org.apache.catalina.core.StandardWrapperValve invoke嚴(yán)重: Servlet.service() for servlet [action] in context with path [] threw exception [java.lang.NullPointerException] with root causejava.lang.NullPointerExceptionat org.quickupstart.struts.action.LoginValidateAction.execute(LoginValidateAction.java:33)at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.quickupstart.common.EncodingFileter.doFilter(EncodingFileter.java:43)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)應(yīng)用在本地跑沒(méi)有一點(diǎn)問(wèn)題，部署到服務(wù)器，一觸發(fā)功能后臺(tái)就拋這個(gè)異常，但是前臺(tái)也沒(méi)有報(bào)HTTP 500錯(cuò)誤，功能運(yùn)行正常。異常里說(shuō)的33行報(bào)紅指針，代碼如下:HttpSession session = request.getSession(false); String validate_code = session.getAttribute("code").toString();//這個(gè)是33行用log4j也可以輸出值。已經(jīng)暈了！抓狂中........................

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5 回答

HUH函數(shù)

TA貢獻(xiàn)1836條經(jīng)驗(yàn) 獲得超4個(gè)贊

兩種情況。
1.獲取到的session對(duì)象為空。
request.getSession(false);如果當(dāng)前有session則返回當(dāng)前session，否則返回null;
request.getSession();如果當(dāng)前有session則返回當(dāng)前session，否則返回一個(gè)新的session。
2.session不為空，session.getAttribute("code")后返回的為空;

用斷點(diǎn)調(diào)試就知道了，另外，凡是設(shè)計(jì)到session的地方，最好是用aop模式進(jìn)行方法前校驗(yàn)。

反對(duì) 回復(fù) 2019-05-06

躍然一笑

TA貢獻(xiàn)1826條經(jīng)驗(yàn) 獲得超6個(gè)贊

為什么用HttpSession session = request.getSession(false);而不是HttpSession session = request.getSession();呢？或者HttpSession session = request.getSession(true);呢

反對(duì) 回復(fù) 2019-05-06