如何使用相对于应用程序的文件路径在服务器上创建文件？

Question

在我的Vaadin spring启动应用程序中,我需要将文件上传到服务器并将其保存在那里.

将文件本地上传到我的桌面工作正常,但我想将应用程序部署到服务器,所以我想将上传的文件保存在相对于我的应用程序的基本路径的目录中.

我创建了一个名为"input_files"的文件夹作为根应用程序文件夹(applicationName - > input_files)的直接子项.上传文件时,应该将文件的内容写入此"input_files"文件夹中新创建的文件.

码:

class FileReceiver implements Upload.Receiver, Upload.SucceededListener {
  private File file;

  public OutputStream receiveUpload(String filename, String mimeType) {
    String basePath = VaadinService.getCurrent().getBaseDirectory().getAbsolutePath();                
    FileOutputStream fileOutputStream;

    try {
      //this line would work:
      //file = new File("/Users/username/Desktop/input_files/" + filename);          

      //this line does not work:
      file = new File(basePath + "/input_files/" + filename);


      fileOutputStream = new FileOutputStream(file);
      labelFilename.setCaption(filename);
    }
    catch (final java.io.FileNotFoundException e) {
      new Notification("Could not open file", e.getMessage(), Notification.Type.ERROR_MESSAGE).show(Page.getCurrent());
      return null;
    }
    return fileOutputStream;
  }

  public void uploadSucceeded(Upload.SucceededEvent event) {

  }
};

重要的代码行是这样的:

file = new File(basePathOfApplication + "/input_files/" + filename);

这条线不起作用.文件input_files夹内没有创建文件.

********************************UPDATE**********************************

屏幕上显示错误消息:

控制台中的错误消息:

com.vaadin.server.UploadException: Upload failed
    at com.vaadin.server.communication.FileUploadHandler.streamToReceiver(FileUploadHandler.java:631) [vaadin-server-8.1.0.jar:8.1.0]
    at com.vaadin.server.communication.FileUploadHandler.handleFileUploadValidationAndData(FileUploadHandler.java:460) [vaadin-server-8.1.0.jar:8.1.0]
    at com.vaadin.server.communication.FileUploadHandler.doHandleSimpleMultipartFileUpload(FileUploadHandler.java:413) [vaadin-server-8.1.0.jar:8.1.0]
    at com.vaadin.server.communication.FileUploadHandler.handleRequest(FileUploadHandler.java:290) [vaadin-server-8.1.0.jar:8.1.0]
    at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1568) [vaadin-server-8.1.0.jar:8.1.0]
    at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:381) [vaadin-server-8.1.0.jar:8.1.0]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_111]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_111]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_111]
Caused by: com.vaadin.server.NoOutputStreamException: null
    at com.vaadin.server.communication.FileUploadHandler.streamToReceiver(FileUploadHandler.java:559) [vaadin-server-8.1.0.jar:8.1.0]
    ... 43 common frames omitted

Answer 1

确保您的应用程序可以在该目录中创建文件/private/var/...。最有可能的是，它不能。我对 Vaadin 不太了解，但该文件夹本身可能是一个“只读”/“临时”目录，用于存储应用程序所需的解压类和数据。此目录可能无意存储任何上传和动态内容。

文档指出：

返回上下文基目录。通常，应用程序以具有应用程序目录的方式部署。对于 Web 应用程序，此目录是 Web 应用程序的根目录。在某些情况下，应用程序可能没有应用程序目录（例如，在 war 中运行的 Web 应用程序）。

所以，它可能是偶数null，这也会破坏你的代码。

恕我直言，最好使用另一个专用目录进行上传，可以通过应用程序配置指定。或者使用众所周知的位置，例如/tmp。

另外，请确保首先使用file.getParentFile().mkdirs().