如何从绝对文件路径制作CommonsMultipartFile？ [英] How to make CommonsMultipartFile from absolute file path?

问题描述

我正在为我的应用程序创建API。在基于GUI浏览器的应用程序中，文件通过表单提交上载。所以我只需要 CommonsMultipartFile file = request.getFile（myfile）。但是，API将以字符串形式提供文件的绝对路径，而不是上载文件。我的应用程序将可以访问此绝对路径。

I'm creating an API for my application. In the GUI browser based application the file is uploaded via a form submission. So I simply do CommonsMultipartFile file = request.getFile(myfile). However, the API will provide an absolute path to the file as a string rather than uploading the file. My application will have access to this absolute path.

因此我不必更改应用程序的基础方法（接受通用接口 MultiPartFile 出于API目的，我想从这个绝对路径读取文件并创建一个 CommonsMultipartFile 对象，该对象可以传递给我已经用于基于GUI浏览器的方法应用程序。

So that I don't have to change the underlying methods of my application (which accept the common interface MultiPartFile For API purposes, I would like to read the file from this absolute path and create a CommonsMultipartFile object which can be passed around to the methods that I am already using for GUI browser based application.

如何执行此操作？ CommonsMultipartFile 的构造函数接受 FileItem

How can I do this? Constructor to CommonsMultipartFile accepts a FileItem

推荐答案

这是特定于API的代码。即不是通常的文件上传代码。

This is API-specific code. i.e. not the usual file upload code.

通常的步骤是：

1. 构建FileItemFactory


2. 构造ServletFileUpload，将其传递给工厂


3. 调用ServletFileUpload.parseRequest（请求）

这回答用独立于servlet的逻辑替换2& 3 - 它避免使用ServletFileUpload（特定于servlet）及其祖先FileUpload（以便用绝对路径名控制文件位置）。注意：（3）通常检查HTTP请求参数以确定传递给FileItemFactory.createItem的较低级别参数 - 这些参数是手动提供的，然后仅用作信息元数据。替换为2& 3：

This answer replaces 2 & 3 with logic independent of servlets - it avoids using ServletFileUpload (servlet-specific) and its ancestor FileUpload (so as to control the file location with an absolute path name). Note: (3) usually examines HTTP request parameters to determine lower-level parameters that are passed to FileItemFactory.createItem - these parameters are instead provided manually, and then only used as informational metadata. Replacement for 2 & 3:

• 构造FileItem（通过FileItemFactory.createItem - 需要手动提供较低级别的参数，通常通过ServletFileUpload.upload（）确定）


• 使用绝对路径写入特定文件


• 通过MultipartFile上传文件

下面提供的请求代码。最后它调用公共代码 - 与Servlet上传共享。

Requested code provided below. At the end it invokes common code - shared with Servlet upload.

// Initialise Apache Commons FileItemFactory for API use only
FileItemFactory fif = new DiskFileItemFactory(sizeThreshold, repositoryBaseDirFile);

// Create Apache Commons FileItem & write file at fullFilePathString into it
FileItem fi = fif.createItem(fieldName, contentType, isFormField, fileName);
fi.write(new java.io.File(new java.net.URI(fullFilePathString));

// Convert FileItem to Spring wrapper: CommonsMultipartFile
org.springframework.web.multipart.MultipartFile mf = new CommonsMultipartFile(fi);

// From here, reuse the same code as the servlet upload.  Operate only upon  
// Spring MultipartFile, but not ServletFileUpload, FileItemFactory etc...

---

参数：

---

Parameters:

• fullFilePathString ：将上传文件的绝对路径（作为字符串）


• fieldName ：表单上的字段名称

• fullFilePathString: absolute path (as String) where file will be uploaded
• fieldName: name of field on the form

（因为避免使用ServletFileUpload& FileUpload，以下仅成为元数据字段，并且不用于控制处理）

(Because ServletFileUpload & FileUpload are avoided, the following become metadata fields only, and are not used to control processing)

• sizeThreshhold ：内存大小阈值（以字节为单位） （通常较小的文件仅使用内存上传，较大的文件上传通过磁盘aded - 但是这个逻辑总是通过磁盘上传文件。默认值= DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD。


• repositoryBaseDireFile ：通常文件上传'temp'目录（作为文件类型），但是这个逻辑使用绝对路径上传文件


• contentType ：表单上字段的内容类型（MIME类型）（如果不是多部分表单字段，则为null）


• isFormField ：如果是普通表单字段，则为true，否则为false，如果是多部分字段。


• fileName ：文件名 - 通常通过表单/客户端指定。

• sizeThreshhold: memory size threshold in bytes (usually files smaller are uploaded using memory only and files larger are uploaded via disk - but this logic has files always uploaded via disk). Default = DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD.
• repositoryBaseDireFile: usually the file upload 'temp' directory (as a File type), but this logic uses an absolute path to upload file
• contentType: content type (MIME type) of field on the form (null if not multi-part form field)
• isFormField: if plain form field, 'true', else false if multi-part field.
• fileName: the name of the file - usually specified via form / client.

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