java - 如何确定多部分POST请求Java的文件大小？

Question

我想在后端处理 POST 请求之前确定文件的大小。考虑一下

@POST
@Consumes(MediaType.MULTIPART_FORM_DATA)
public Response uploadFile(
        @FormDataParam("file") InputStream uploadedInputStream,
        @FormDataParam("file") FormDataContentDisposition fileDetail) throws IOException {
         String uploadedFileLocation = "somePath" + fileDetail.getFileName();
        // save it
    writeToFile(uploadedInputStream, uploadedFileLocation);
    String output = "File uploaded to : " + uploadedFileLocation;
    return Response.ok(output).build();
}

// save uploaded file to new location
private void writeToFile(InputStream uploadedInputStream, String uploadedFileLocation) throws IOException {
    int read;
    final int BUFFER_LENGTH = 1024;
    final byte[] buffer = new byte[BUFFER_LENGTH];
    OutputStream out = new FileOutputStream(new File(uploadedFileLocation));
    while ((read = uploadedInputStream.read(buffer)) != -1) {
        out.write(buffer, 0, read);
    }
    out.flush();
    out.close();
}

我看到我可以使用 Content-Disposition 来获取文件大小。如何获取 Content-Disposition header 来获取长度，或者是否应该有一个函数来检查输入流的大小？

Answer 1

您可以使用@HeaderParam来获取命名 header 的值。

@POST
@Consumes(MediaType.MULTIPART_FORM_DATA)
public Response uploadFile(
    @FormDataParam("file") InputStream uploadedInputStream,
    @FormDataParam("file") FormDataContentDisposition fileDetail,
    @HeaderParam("Content-Disposition") String contentDisposition
) throws IOException { 

请注意，假设您使用的是 DOM File API 和 fetch 等功能，您仍然需要将文件大小添加到客户端的 header 中。