报错：java.lang.NullPointerException 空指针异常

项目场景

当用Java做项目管理系统登录页面的时，涉及到一些安全问题需要用到Shiro(Java安全锁框架）、ajax，

问题描述：

当用到ajax做验证登录的时候，报空指针异常java.lang.NullPointerException

运行页面

页面一直刷新，却登录不进去系统页面，看了idea控制板，发现却报了空指针异常

异常语块

java.lang.NullPointerException at
com.qhit.controller.LoginController.login(LoginController.java:28) at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498) at
org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
at
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
at
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:690)
at
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
at
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
at
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
at
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:863)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) at
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at
org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
at
org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
at
org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
at
org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
at
org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
at
org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
at
org.apache.shiro.web.servlet.AbstractShiroFilter1.call(AbstractShiroFilter.java:365)atorg.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)atorg.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)atorg.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)atorg.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)atorg.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)atorg.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)atorg.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)atorg.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)atorg.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)atorg.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)atorg.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)atorg.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)atorg.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)atorg.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)atorg.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)atorg.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)atorg.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)atorg.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)atorg.apache.coyote.AbstractProtocol1.call(AbstractShiroFilter.java:365) at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383) at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344) at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol1.call(AbstractShiroFilter.java:365)atorg.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)atorg.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)atorg.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)atorg.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)atorg.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)atorg.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)atorg.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)atorg.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)atorg.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)atorg.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)atorg.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)atorg.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)atorg.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)atorg.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)atorg.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)atorg.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)atorg.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)atorg.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)atorg.apache.coyote.AbstractProtocolConnectionHandler.process(AbstractProtocol.java:790)
at
org.apache.tomcat.util.net.NioEndpointSocketProcessor.doRun(NioEndpoint.java:1468)atorg.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)atjava.util.concurrent.ThreadPoolExecutorSocketProcessor.doRun(NioEndpoint.java:1468) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutorSocketProcessor.doRun(NioEndpoint.java:1468)atorg.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)atjava.util.concurrent.ThreadPoolExecutorWorker.run(ThreadPoolExecutor.java:624)
at
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

正确写法

把date改成data

总结：

就是在写代码的时候把data和date写混了，造成了运行异常，找了好久才找到这个错误。

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