Java NullPointerException: 获取用户信息时出现空指针异常

{"title":"Java NullPointerException: 获取用户信息时出现空指针异常","description":"本文档将解释在Java代码中获取用户信息时出现空指针异常（NullPointerException）的原因，并提供可能的解决方法。","keywords":"Java, NullPointerException, 空指针异常, 获取用户信息, SessionUtils, SecurityUtils, userInfoDTO","content":"public static UserInfoDTO getUserInfo() {\n WhitelistSetting curUser = SessionUtils.getCurUser();\n Admin userInfo = SessionUtils.getCurrentUserInfo();\n UserInfoDTO userInfoDTO = new UserInfoDTO();\n //模拟登录\n// if (curUser == null) {\n// userInfoDTO.setId(1L);\n// userInfoDTO.setName("模拟用户");\n// userInfoDTO.setUserType(2L);\n// }else{\n userInfoDTO.setId(curUser.getId());\n userInfoDTO.setName(curUser.getName());\n userInfoDTO.setUserType(curUser.getRoleId());\n// }\n\n return userInfoDTO;\n }\n报错\njava.lang.NullPointerException: null\n\tat com.example.mybatisplus.common.utls.SecurityUtils.getUserInfo(SecurityUtils.java:39) ~[classes/:na]\n\tat com.example.mybatisplus.web.controller.AuthController.getUserInfo(AuthController.java:20) ~[classes/:na]\n\tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]\n\tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]\n\tat java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]\n\tat java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]\n\tat org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat javax.servlet.http.HttpServlet.service(HttpServlet.java:529) ~[tomcat-embed-core-9.0.76.jar:4.0.FR]\n\tat org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.28.jar:5.3.28]\n\tat javax.servlet.http.HttpServlet.service(HttpServlet.java:623) ~[tomcat-embed-core-9.0.76.jar:4.0.FR]\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.28.jar:5.3.28]\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:390) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:926) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1791) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.76.jar:9.0.76]\n\tat java.base/java.lang.Thread.run(Thread.java:829) ~[na:na]\n为什么\n内容：报错是因为在代码中出现了空指针异常（NullPointerException）。具体的错误信息是在SecurityUtils类的第39行，也就是在获取当前用户信息时发生了空指针异常。\n\n根据代码分析，可能的原因有以下几点：\n\n1. curUser变量为空：在第3行代码中，通过SessionUtils.getCurUser()方法获取当前用户信息赋值给curUser变量。如果该方法返回null，那么curUser变量就为空。可以检查一下SessionUtils.getCurUser()方法的实现，确保它能正确返回当前用户信息。\n\n2. userInfo变量为空：在第4行代码中，通过SessionUtils.getCurrentUserInfo()方法获取当前用户信息赋值给userInfo变量。如果该方法返回null，那么userInfo变量就为空。可以检查一下SessionUtils.getCurrentUserInfo()方法的实现，确保它能正确返回当前用户信息。\n\n3. userInfoDTO变量为空：在第6行代码中，创建了一个UserInfoDTO对象并赋值给userInfoDTO变量。如果UserInfoDTO的构造函数中有可能发生空指针异常，那么在创建对象时就会抛出该异常。可以检查一下UserInfoDTO的构造函数的实现，确保它能正确初始化对象。\n\n根据具体的业务逻辑，可以针对以上可能的原因进行调试和排查，找到导致空指针异常的具体原因，并进行修复。