Servlet.service() for servlet UserServlet threw exception java.lang.NullPointerException 空指针异常

错误付现:

严重: Servlet.service() for servlet UserServlet threw exception
java.lang.NullPointerException
at com.liuyang.servlet.UserServlet.doGet(UserServlet.java:17)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:615)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:612)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:503)
at java.lang.Thread.run(Thread.java:662)

这个错误是我的前端界面输入的值无法传递到后台,所以后台无法获取.

代码定位

到了这行,但是这行没有错误,那么就找跟它相关的代码,传递的值是username的值,所以找有关username的语句,后端的代码在编译器未报错,说明错误不在后端

所以去前端找问题.

最后发现是

这里出错了,不是$而是&符号所以导致值无法传递.

时间： 2024-10-13 01:37:05

Servlet.service() for servlet UserServlet threw exception java.lang.NullPointerException 空指针异常的相关文章

报错！！！Servlet.service() for servlet [action] in context with path [/myssh] threw exception [java.lang.NullPointerException] with root cause java.lang.NullPointerException

这个为什么报错啊~~ at com.hsp.basic.BasicService.executeQuery(BasicService.java:33) 这个对应的语句是   Query query =this.sessionFactory.getCurrentSession().createQuery(hql); Sep 24, 2017 11:39:50 PM org.apache.catalina.core.StandardWrapperValve invoke 严重: Servlet.se

严重: Servlet.service() for servlet [jsp] threw exception java.lang.NullPointerException

五月 04, 2018 11:53:24 上午 org.apache.catalina.core.ApplicationDispatcher invoke 严重: Servlet.service() for servlet [jsp] threw exception java.lang.NullPointerException at org.apache.jsp.tag.web.partyRoleId_tag.doTag(partyRoleId_tag.java:125) at org.apac

（未解决）严重:threw exception java.lang.NullPointerException

问题描述: Servlet.service() for servlet [servlet.AddModuleServlet] in context with path [/PermissionSystem] threw exception java.lang.NullPointerException 添加数据库时,空指针. AddModule.jsp在Module文件夹外则没有问题. 但form中添加路径了啊:<form action="<%=request.getContextPa

严重: End event threw exception java.lang.IllegalArgumentException: Can&#39;t convert argument: null

堆栈信息: 2014-6-17 10:33:58 org.apache.tomcat.util.digester.Digester endElement 严重: End event threw exception java.lang.IllegalArgumentException: Can't convert argument: null at org.apache.tomcat.util.IntrospectionUtils.convert(IntrospectionUtils.java:1

异常-User class threw exception: java.lang.IllegalStateException: Cannot call methods on a stopped SparkContext.

1 详细信息 User class threw exception: java.lang.IllegalStateException: Cannot call methods on a stopped SparkContext. This stopped SparkContext was created at: org.apache.spark.SparkContext.<init>(SparkContext.scala:76) com.wm.bigdata.spark.etl.RentOrd

在Servlet使用getServletContext()获取ServletContext对象出现java.lang.NullPointerException(空指针)异常的解决办法

今天遇到了一个在servlet的service方法中获取ServletContext对象出现java.lang.NullPointerException(空指针)异常,代码如下: 1 //获取ServletContext对象 2 ServletContext servletContext = this.getServletContext(); 这个问题很奇怪,也是第一次遇到,因为以前在servlet的doGet/doPost方法中要获取ServletContext对象时都是这样写的,也没有出现过

JavaWeb学习(5.5)---在Servlet使用getServletContext()获取ServletContext对象出现java.lang.NullPointerException(空指针)异常的解决办法

本文整理自孤傲苍狼大大的博客,,, 在servlet的service方法中获取ServletContext对象也行出现java.lang.NullPointerException(空指针)异常,代码如下: 1 //获取ServletContext对象 2 ServletContext servletContext = this.getServletContext(); 原来是重写了 init(ServletConfig)方法,但重写的init方法内部没有调用super.init(config);

java.lang.NullPointerException 空指针异常

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.heheh.daima/com.heheh.daima.HeaderImgListActivity} Android中出错常见的几种情况: 1.对象没有初始化就被调用 2.setContentView()中布局文件引用错误 3.引用对象为null 这个异常最常见,其实都是对象引用错误和为null的情况,我这里指出3点是为了能准确定位查找错误而已,如果你也报

Servlet.service() for servlet [jsp] in context ....错误

Servlet.service() for servlet [jsp] in context with path [/mvcTest] threw exception [java.lang.NullPointerException] with root causejava.lang.NullPointerException这是在用tomcat写一个小应用时遇到的错误,在网上看了很多没看明白,最终试错n次后发现了问题, 其实这个问题(我遇到的那种情况,可能这个报错不止我遇到的这种情况导致)的根本原