如何使用相對於應用程序的文件路徑在服務器上創建文件？

Question

在我的Vaadin spring啟動應用程序中，我需要將文件上傳到服務器並將其保存在那里。

將文件本地上傳到我的桌面工作正常，但我想將應用程序部署到服務器，所以我想將上傳的文件保存在相對於我的應用程序的基本路徑的目錄中。

我創建了一個名為“input_files”的文件夾作為根應用程序文件夾（applicationName - > input_files）的直接子項。 上傳文件時，應該將文件的內容寫入此“input_files”文件夾中新創建的文件。

碼：

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) {

  }
};

重要的代碼行是這樣的：

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

這條線不起作用。 在input_files文件夾中沒有創建文件。

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

屏幕上顯示錯誤消息：

控制台中的錯誤消息：

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

確保您的應用程序可以在目錄/private/var/...創建文件。 最有可能的是，它不可能。 我對Vaadin知之甚少，但文件夾本身可能是一個“只讀”/“臨時”目錄，用於存儲應用程序所需的解壓縮類和數據。 此目錄可能無意存儲任何上載和動態內容。

文件說明：

返回上下文基目錄。 通常，應用程序以具有應用程序目錄的方式部署。 對於Web應用程序，此目錄是Web應用程序的根目錄。 在某些情況下，應用程序可能沒有應用程序目錄（例如，在戰爭中運行的Web應用程序）。

所以，它甚至可能為null ，這也會破壞你的代碼。

恕我直言，最好使用另一個專用目錄進行上傳，可以通過應用程序配置指定。 或者使用知名的位置，例如/tmp 。

此外，請確保首先使用file.getParentFile().mkdirs()創建父目錄。

Answer 2

根據Vaadin論壇 ，你不應該在Vaadin服務中保存文件，

你應該在app.getContext().getBaseDirectory()保存文件app.getContext().getBaseDirectory()

• 注意：app是com.vaadin.Application

您可以檢查一個樣本 ，該樣本也檢查屬性，以防它不起作用：

 // cannot access example directory, possible security issue with
// Application Server or Servlet Container
// Try to read sample directory from web.xml parameter
if (application.getProperty("sampleDirectory") != null) {
                file = new File(application.getProperty("sampleDirectory"));
                if ((file != null) && (file.canRead())
                        && (file.getAbsolutePath() != null)) {
                    // Success using property
                    return file;
                }

Answer 3

您的文件夾沒有權限，請嘗試為/tmp提供完全權限

drwxrwxrwt  15 root root 4.0K Nov  4 20:23 tmp

使用sudo chmod 777 /opt/myapp/input_files/

之后嘗試執行您的代碼。

注意：我使用/ opt / use也可以使用任何其他文件夾，但記得給它​​許可。