Java文件上传遇FileNotFoundException问题求助（同事代码正常）

点击上传按钮时，屏幕和控制台返回两类错误：

java.io.FileNotFoundException: /tmp/Filename.docx (No such file or directory)- (permission denied)
java.io.FileNotFoundException: /tmp/MAXWEL-OCHIENG-CAD-Assignment1-.docx (No such file or directory)

协作同事的代码运行完全正常，但本地环境出现该问题，相关上传代码如下：

public static String uploadClientCaseFiles(HttpServletRequest request, HttpServletResponse response)
        throws IOException{

    LocalDispatcher dispatcher = (LocalDispatcher) request.getAttribute("dispatcher");
    DispatchContext dctx =  dispatcher.getDispatchContext();
    Delegator delegator = dctx.getDelegator();

    String uploadedBy = "";
    String folderName = "";
    String caseId = "";
    String clientId = "";
    String comments = "";
    String fieldName = "";
    String fieldValue = "";
    String gdriveFileId = "";

    Drive service = null;

    int maxFileSize = 5000 * 1024;
    int maxMemSize = 100 * 1024;

    Map<String, Object> result;
    File file;
    boolean isMultipart = ServletFileUpload.isMultipartContent(request);
    String fileName = "";
    String tempDir = System.getProperty("java.io.tmpdir");

    try {
        service = GoogleDriveAPI.getDriveService();
    } catch (IOException | GeneralSecurityException e) {
        e.printStackTrace();
    }
    if(!isMultipart){
        //result = ServiceUtil.returnError("Unable to upload file");
        return("uploadFailed");
    }
    DiskFileItemFactory factory = new DiskFileItemFactory();
    // maximum size that will be stored in memory
    factory.setSizeThreshold(maxMemSize);
    // Location to save data that is larger than maxMemSize.
    factory.setRepository(new File(tempDir));
    // Create a new file upload handler
    ServletFileUpload upload = new ServletFileUpload(factory);
    // maximum file size to be uploaded.
    upload.setSizeMax(maxFileSize);

    try{
        // Parse the request to get file items.
        List fileItems = upload.parseRequest(request);
        // Process the uploaded file items
        Iterator i = fileItems.iterator();
        while (i.hasNext())
        {
            FileItem fi = (FileItem)i.next();

            if (!fi.isFormField())
            {
                // Get the uploaded file parameters
                fieldName = fi.getFieldName();
                fileName = fi.getName();
                fileName = fileName.replaceAll("\\s","-");

                // Write the file
                if( fileName.lastIndexOf("\\\\") >= 0 ){
                    file = new File(tempDir +
                    fileName.substring(fileName.lastIndexOf("\\\\")));
                }else{
                    file = new File(tempDir +
                    fileName.substring(fileName.lastIndexOf("\\\\")+1));
                }
                fi.write(file);

            } else {
                fieldName = fi.getFieldName();
                fieldValue = fi.getString();
                if (fieldName.equals("uploadedBy")) {
                    //logic goes here...
                    uploadedBy = fieldValue;
                } else if (fieldName.equals("comments")) {
                    //next logic goes here...
                    comments = fieldValue;
                } else if(fieldName.equals("caseId")){
                    caseId = fieldValue;

                }else if (fieldName.equals("clientId")) {
                    //next logic goes here...
                    clientId = fieldValue;
                }
            //                    else if (fieldName.equals("folderName")) {
                //                        //next logic goes here...
            //                        folderName = fieldValue;
            //                    }
            }
        }

    } catch(Exception ex) {
        System.out.println(ex);
    }

    // GenericValue folderName = null;
    // try {
    //  folderName = delegator.findOne("FolderDriveMapping",
    //          UtilMisc.toMap("folderName",
    //                  folderName), false);
    // } catch (GenericEntityException e2) {
    //  e2.printStackTrace();
    // }
    // if (folderName.f) {

    // }

    // Upload to google drive
    com.google.api.services.drive.model.File fileMetadata = new com.google.api.services.drive.model.File();
    fileMetadata.setName(fileName);
    fileMetadata.setParents(Collections.singletonList("1q9QFwXGmmT6xNHDl5qauIkOqi0PYwWnf"));
    java.io.File filePath = new java.io.File(tempDir + "/" + fileName);
    FileContent mediaContent = new FileContent("application/pdf", filePath);
    com.google.api.services.drive.model.File clientFile = service.files().create(fileMetadata, mediaContent)
            .setFields("id, name, webContentLink, webViewLink")
            .execute();

    gdriveFileId = clientFile.getId();

    /* Get file properties: Id, Name, Link */
    log.info("########################## File Name: " + clientFile.getName());
    log.info("########################## File ID: " + clientFile.getId());
    log.info("########################## Download Link: " + clientFile.getWebContentLink());
    log.info("########################## View Link: " + clientFile.getWebViewLink());

          GenericValue setup = delegator.makeValue("ClientCaseFiles");
          String clientCaseFilesId = delegator.getNextSeqId("ClientCaseFiles");


    String ext = fileName.substring(fileName.length() - 3);
    String mimeType = "";

    if((ext.equals("doc")) || (ext.equals("dot")) || (ext.equals("ocx"))){
        mimeType = "application/msword";

    } else if(ext.equals("pdf")){
        mimeType = "application/pdf";

    } else if((ext.equals("ppt")) || (ext.equals("ppz")) || (ext.equals("ptx"))){
        mimeType = "application/mspowerpoint";

    } else if((ext.equals("xls")) || (ext.equals("lsx")) || (ext.equals("xlt"))){
        mimeType = "application/x-msexcel";

    } else if(ext.equals("zip")){
        mimeType = "application/zip";

    } else{
        mimeType = "text/plain";
    }


    setup.put("clientCaseFilesId", clientCaseFilesId);
    setup.put("fileName", fileName);
    setup.put("caseId", caseId);
    setup.put("clientId", clientId);
    setup.put("comments", comments);
    setup.put("uploadedBy", uploadedBy);
    setup.put("mimeType", mimeType);
    setup.put("extension", ext);


    try {
        setup.create();
    } catch (GenericEntityException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    response.sendRedirect("casefiles?clientId="+clientId+"&caseId="+caseId);
    return("uplodedSuccesfully");
}

问题原因分析 #

1. 权限不足：本地/tmp目录（Windows对应系统临时目录）没有写入权限，导致无法创建临时文件
2. 路径拼接错误：代码中手动处理路径分隔符的逻辑存在漏洞，不同操作系统（Windows/Unix）下路径格式不兼容，导致生成的文件路径无效
3. 异常处理不严谨：捕获异常后仅打印日志，未终止后续流程，导致后续尝试读取未创建成功的文件时触发新异常

解决方案 #

1. 修复路径拼接逻辑 #

用File类的构造方法自动处理路径分隔符，避免系统差异：

// 替换原路径拼接代码
// 获取纯文件名（去掉客户端传来的路径部分）
String simpleFileName = new File(fileName).getName();
simpleFileName = simpleFileName.replaceAll("\\s","-");
// 用File构造方法拼接路径，自动适配系统分隔符
file = new File(tempDir, simpleFileName);
fi.write(file);

2. 修复临时目录权限 #

• Unix/Linux/macOS：执行命令赋予/tmp写入权限

  chmod 777 /tmp
  

  或检查运行程序的用户是否拥有/tmp目录的写入权限
• Windows：找到系统临时目录（一般为C:\Users\<你的用户名>\AppData\Local\Temp），右键设置当前用户的写入权限

3. 完善异常处理 #

文件写入失败时直接终止流程，避免后续无效操作：

try{
    // ... 其他代码
    fi.write(file);
} catch(IOException ioEx) {
    System.err.println("写入临时文件失败: " + ioEx.getMessage());
    return "uploadFailed";
} catch(Exception ex) {
    System.err.println("上传处理异常: " + ex.getMessage());
    return "uploadFailed";
}

4. 提前验证临时目录有效性 #

在代码开头添加目录检查，确保临时目录存在且可写：

String tempDir = System.getProperty("java.io.tmpdir");
File tempDirFile = new File(tempDir);
if (!tempDirFile.exists()) {
    tempDirFile.mkdirs();
}
if (!tempDirFile.canWrite()) {
    System.err.println("临时目录无写入权限: " + tempDir);
    return "uploadFailed";
}

内容的提问来源于stack exchange，提问作者MAXWEL OCHIENG