java - springmvc osx windows servlet maven

Question

我有一个网络应用程序。它在 iosx 上运行良好。但是，如果我将项目(mavenproject)导入我的 virtualbox 到 Windows 10(使用 git 克隆并使用 mavenproject 导入到 eclipse)。如果我想将某些内容上传到服务器，我会收到错误消息。“请求的资源不可用。”要查看上传页面，我有以下 Controller :

@RequestMapping(value = "/erstellen", method = RequestMethod.GET)
    public String zeigErstellenForm() {
        System.out.println("im here");
        return "dateien_upload_erstellen";
    }

可以看到上传页面，所以我猜这个函数被调用了，但它没有打印“我在这里”。我不明白这是怎么回事。

浏览器错误:

type Exception report

message Request processing failed; nested exception is java.lang.NullPointerException

description The server encountered an internal error that prevented it from fulfilling this request.

exception org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:981) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:871) javax.servlet.http.HttpServlet.service(HttpServlet.java:648) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause java.lang.NullPointerException de.bla.blabla.Services.OrdnerErstellen.namePruefen(OrdnerErstellen.java:52) de.bla.blabla.Services.OrdnerErstellen.randomName(OrdnerErstellen.java:33) de.bla.blabla.Services.OrdnerErstellen.(OrdnerErstellen.java:17) de.bla.blabla.Controller.DateiUploadController.save(DateiUploadController.java:52) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:178) org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:444) org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:432) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:871) javax.servlet.http.HttpServlet.service(HttpServlet.java:648) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

eclipse 错误:

SCHWERWIEGEND: Servlet.service() for servlet [test] in context with path [/testMaven] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause java.lang.NullPointerException at de.bla.blabla.Services.OrdnerErstellen.namePruefen(OrdnerErstellen.java:52) at de.bla.blabla.Services.OrdnerErstellen.randomName(OrdnerErstellen.java:33) at de.bla.blabla.Services.OrdnerErstellen.(OrdnerErstellen.java:17) at de.bla.blabla.Controller.DateiUploadController.save(DateiUploadController.java:52) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:178) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:444) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:432) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:871) at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source)

我使用:

• Tomcat 8
• eclipse

服务小程序:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

<context:component-scan base-package="de.bla.blabla.Controller"/>


 <bean id="multipartResolver"
  class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>

<mvc:annotation-driven />
<mvc:resources mapping="/resources/**" location="/resources/"/>

  <bean id="jspViewResolver"
    class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
  </bean>
</beans>

web.xml:

<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
          http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">  <display-name>test</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>test</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
        <servlet-name>test</servlet-name>
        <url-pattern>*.html</url-pattern>
        <url-pattern>/download</url-pattern>
        <url-pattern>/read</url-pattern>
    </servlet-mapping>

</web-app>

项目中没有错误。我清理所有更新的 maven 等。

Answer 1

您不能在 JSP 中显示系统输出消息!

在你的 webapp 的 WEB-INF/jsp 目录中，创建一个文件 index.jsp 并在这些 JSP 中写入你的 helloWorld 消息。

除非您遗漏了其他内容，否则它会起作用。

或者如果你想使用模型，在你的 Controller 中像下面这样:

ModelAndView mav = new ModelAndView();
mav.addObject("message", "hello world");
return mav;

对于您的空指针异常，我将尝试使用您的 eclipse 平台进行远程调试，并在行内设置一些断点:

de.bla.blabla.Services.OrdnerErstellen.namePruefen(OrdnerErstellen.java:52)

在 de.bla.blabla.Services.OrdnerErstellen.randomName(OrdnerErstellen.java:33)

在 de.bla.blabla.Services.OrdnerErstellen.(OrdnerErstellen.java:17)

在 de.bla.blabla.Controller.DateiUploadController.save(DateiUploadController.java:52)