【发布时间】：2020-02-03 02:49:50
【问题描述】：
我正在创建一个包含教授字段的表单，这些字段是 id (long)、nome(string)、username (string)、email(string) 和 curso_coord(curso)，因为 curso 是类课程的参考变量。
在表单中，输入用户名、姓名和电子邮件字段供用户填写，如果他/她是该课程的协调员，则该课程是用户选择课程的选择，如果不是，则为 -1
我尝试使用 curso.get(0).getId() 来解决问题，但还不够
@Controller
@RequestMapping(value = { "/professor" })
public class ProfessorController {
@Autowired
ProfessorRepository pr;
CursoRepository c;
@GetMapping(value = "")
@ResponseBody
public ModelAndView professorInicio() {
ModelAndView form = new ModelAndView("/form");
form.addObject("professor", new Professor());
List<Curso> curso = c.findAll();
curso.get(0).getId();
form.addObject("curso", curso);
return form;
}
@PostMapping(value = "")
@ResponseBody
public ModelAndView cadastraProfessor(@ModelAttribute ("professor") Professor professor){
//Professor prof = new Professor();
ModelAndView index = new ModelAndView("/index");
professor.getUsername();
professor.getEmail();
professor.getNome();
professor.getCursoCoord();
pr.save(professor);
return index;
}
....
}
<form th:action="@{/professor}" th:object = "${professor}" method="POST">
<div class = "form-group">
<label for = "username">Username</label>
<input type = "text" th:field = "*{username}" autofocus = "autofocus"/>
</div>
<div class = "form-group">
<label for = "nome">Nome</label>
<input type = "text" th:field = "*{nome}" autofocus = "autofocus"/>
</div>
<div class = "form-group">
<label for = "email">Email</label>
<input type = "hidden" name="email" value="">
<input type = "text" th:field = "*{email}" autofocus = "autofocus"/>
</div>
<div class = "form-group">
<select th:field = "*{curso_coord}">
<option
th:each = "c: ${cursos}"
th:value = "${c.id}">Cursos
</option>
<option value = -1> Não Coordenador
</option>
</select>"
</div>
<button type = "submit" class = "btn btn-success ">Salvar</button>
</form>
2019-10-04 15:37:00.700 错误 17580 --- [nio-8081-exec-1] c.p.p.controller.ErrorController : 算法错误！
java.lang.NullPointerException: null 在 com.planoensino.planoensino.controller.ProfessorController.professorInicio（ProfessorController.java:35） 〜[主要/：na] 在 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181] 在 sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181] 在 sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181] 在 java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181] 在 org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) [spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866) [spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 javax.servlet.http.HttpServlet.service(HttpServlet.java:687) [javax.servlet-api-3.1.0.jar:3.1.0] 在 org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) [spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [javax.servlet-api-3.1.0.jar:3.1.0] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:320) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:119) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:66) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) [spring-security-web-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.springframework.session.web.http.SessionRepositoryFilter.doFilterInternal(SessionRepositoryFilter.java:147) [spring-session-core-2.0.5.RELEASE.jar:2.0.5.RELEASE] 在 org.springframework.session.web.http.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:81) [spring-session-core-2.0.5.RELEASE.jar:2.0.5.RELEASE] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE] 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:198） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:96） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:493） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:140） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:81） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:87） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:342） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.coyote.AbstractProcessorLight.process（AbstractProcessorLight.java:66） [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:800) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1471) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_181] 在 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_181] 在 org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.32.jar:8.5.32] 在 java.lang.Thread.run(Thread.java:748) [na:1.8.0_181]
2019-10-04 15:37:00.702 警告 17580 --- [nio-8081-exec-1] .m.m.a.ExceptionHandlerExceptionResolver : 已解决的异常导致 通过Handler执行：java.lang.NullPointerException
【问题讨论】：
标签： spring spring-boot spring-mvc model-view-controller nullpointerexception