FileNotFoundException（是一个目录）

Question

我目前正在尝试上传多个文件，这些文件正在正确上传到目标目录中。但是在日志中它给了我这个错误：

java.io.FileNotFoundException: /home/sandeep/java_proj/jee_tut/files (Is a directory)

at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:221)
at java.io.FileOutputStream.<init>(FileOutputStream.java:171)
at com.jee.controller.FileProcessing.uploadFiles(FileProcessing.java:35)
at com.jee.controller.View.doPost(View.java:48)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

这是我上传文件的代码：

final String UPLOAD_DIR="files";

    String applicationPath="/home/sandeep/java_proj/jee_tut";
    String uploadDirPath= applicationPath + File.separator + UPLOAD_DIR;

    try{
        File fileDir=new File(uploadDirPath);
        if(!fileDir.exists()){
            fileDir.mkdirs();
        }
        InputStream inputStream= null;
        OutputStream outputStream = null;
        try{
            for(Part part:request.getParts()){
                String fileName=getFileName(part);

                    File outputPath=new File(uploadDirPath + File.separator + fileName);
                    inputStream = part.getInputStream();
                    outputStream = new FileOutputStream(outputPath);

                    int read = 0;
                    final byte[] bytes = new byte[1024];
                    while((read=inputStream.read(bytes)) != -1){
                        outputStream.write(bytes, 0, read);
                    }
                System.out.println(fileName);
            }
        }catch(Exception e){
            e.printStackTrace();
            return "";
        }
        finally{
            if(inputStream != null){
                inputStream.close();
            }
            if(outputStream != null){
                outputStream.close();
            }
        }
        return uploadDirPath;

    }catch(Exception e){
        e.printStackTrace();
        return "";
    }

由于我是 java 的新手，我不确定为什么会出现此错误。我该如何调试？

Answer 1

看起来在某些情况下 filename 是空白或空的，所以 File outputPath=new File(uploadDirPath + File.separator + fileName); 将是一个目录，这里 new FileOutputStream(outputPath); 您尝试写入目录而不是文件。所以你应该检查 filename 是否不为空。

Answer 2

您的代码中有很多错误。其一，您只关闭 last InputStreams 和 OutputStreams；你应该关闭它们中的每一个。你在这里做事的方式，你有资源泄漏。

其次，这是2015年；因此删除 File 并使用 java.nio.file 代替；另外，使用 try-with-resources。

第三：你现在在项目目录下上传；当应用程序在服务器上运行 "live" 时不要这样做，这显然是行不通的。

样本：

private static final Path BASEDIR = Paths.get("/path/to/upload/directory");

// in the upload method:

Files.createDirectories(BASEDIR);

String fileName;
Path path;

for (final Part part: request.getParts()) {
    fileName = getFileName(part);

    if (fileName.isEmpty())
        continue;

    path = BASEDIR.resolve(fileName);

    try (
        final InputStream in = part.getInputStream();
    ) {
        Files.copy(in, path, StandardOpenOption.CREATE_NEW);
    }
}

Answer 3

这个错误发生在我身上是因为我使用 file.mkdirs() 和完整的文件名。

假设你的文件路径是emulated/0/test/images/img.jpg

然后从路径中删除最后一部分并对结果文件

使用file.mkdirs()

File file = new File("emulated/0/test/images/")

if (!file.exists()) {
    file.mkdirs();
}

FileNotFoundException（是一个目录）

FileNotFoundException (Is a Directory)

java

jakarta-ee

file-upload

multipartform-data