听起来你想用Java中的Http Trigger通过HTML表单上传一个文件到你的Azure函数，该表单包含如下＜code＞multipart/form data＜/code＞。

<form method="POST" enctype="multipart/form-data" action="https://<your function app>/api/HttpTrigger-Java">
  File to upload: <input type="file" name="upfile"><br/>
  Notes about the file: <input type="text" name="note"><br/>
  <br/>
  <input type="submit" value="Press"> to upload the file!
</form>

但是，没有任何类实现接口 HttpRequestMessage

根据我的经验，唯一的方法是解析< code>multipart/form-data请求的头和体来获取文件。有一个类似SO thread库的回答和问题所有者发布的从inputstream解析multipart/form-data的例子，其中包括使用Apache Commons FileUpload的< code>MultipartStream类的代码，在我测试后可以工作。

以下是从Azure Function for Java收到的< code>multipart/form-data请求的< code>Content-Type头和正文。

标题Content-Type

content-type: multipart/form-data; boundary=----WebKitFormBoundaryT2TWuevX3RIYWRQF

多部分/表单数据请求正文

------WebKitFormBoundaryT2TWuevX3RIYWRQF
Content-Disposition: form-data; name="upfile"; filename="z.txt"
Content-Type: text/plain
1234
ABCD
------WebKitFormBoundaryT2TWuevX3RIYWRQF
Content-Disposition: form-data; name="note"
test.txt
------WebKitFormBoundaryT2TWuevX3RIYWRQF--

这是我获取文件的示例代码。

@FunctionName("HttpTrigger-Java")
public HttpResponseMessage run(
        @HttpTrigger(name = "req", methods = {HttpMethod.GET, HttpMethod.POST}, authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Optional<String>> request,
        final ExecutionContext context) {
    String contentType = request.getHeaders().get("content-type"); // Get content-type header
    // here the "content-type" must be lower-case
    String body = request.getBody().get(); // Get request body
    InputStream in = new ByteArrayInputStream(body.getBytes()); // Convert body to an input stream
    String boundary = contentType.split(";")[1].split("=")[1]; // Get boundary from content-type header
    int bufSize = 1024;
    MultipartStream multipartStream  = new MultipartStream(in, boundary.getBytes(), bufSize, null); // Using MultipartStream to parse body input stream
    // the code below comes from the SO thread above
    // you can fetch a file content from readBodyData 
    // after the headers Content-Disposition: form-data; name="upfile"; filename="test.txt" \n Content-Type: text/plain
    boolean nextPart = multipartStream.skipPreamble();
    while (nextPart) {
        String header = multipartStream.readHeaders();
        System.out.println("");
        System.out.println("Headers:");
        System.out.println(header);
        System.out.println("Body:");
        multipartStream.readBodyData(System.out);
        System.out.println("");
        nextPart = multipartStream.readBoundary();
    }
    return request.createResponseBuilder(HttpStatus.OK).body("Success").build();
}

上面代码在终端中的输出:

Headers:
Content-Disposition: form-data; name="upfile"; filename="test.txt"
Content-Type: text/plain


Body:
1234
ABCD


Headers:
Content-Disposition: form-data; name="note"


Body:
test.txt

更新：如果上传图片，上面代码的输出如下。

Headers:
Content-Disposition: form-data; name="upfile"; filename="test.jpg"
Content-Type: image/png


Body:
<the binary content of an image>

因此，您可以解析标头以获取< code>filename值，并使用< code>FileOutputStream来存储它，如下面的代码所示。

while(nextPart) {
    String header = multipartStream.readHeaders();
    System.out.println("");
    System.out.println("Headers:");
    System.out.println(header);
    System.out.println("Body:");
    if (header.contains("Content-Type: image/")) {
        int start = header.indexOf("filename=")+"filename=".length()+1;
        int end = header.indexOf("\r\n")-1;
        String filename = header.substring(start, end);
        System.out.println(filename);
        FileOutputStream fos = new FileOutputStream(filename);
        multipartStream.readBodyData(fos);
    } else {
        multipartStream.readBodyData(System.out);
    }
    System.out.println("");
    nextPart = multipartStream.readBoundary();
}

更新2:

我发现似乎有一个Java的Azure函数的问题，这可能是一个错误，当上传二进制文件时会丢失一些字节，但上传文本文件时不会发生。因此，一个变通的解决方案是在浏览器中将上传文件转换为base64字符串以发布到Azure函数，并在Azure函数中转换上传到原始二进制文件的base64内容。

这是我测试的超文本标记语言代码。

File to upload: <input type="file" name="upfile" id="fileup"><br/>
<form method="POST" enctype="multipart/form-data" action="http://localhost:7071/api/HttpTrigger-Java">
  Notes about the file: <input type="text" name="note"><br/>
  <input type="hidden" name="file_base64" id="file_base64"><br/>
  <input type="submit" value="Press"> to upload the file!
</form>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">/script>
<script>
$(document).ready(function(){
    $("#fileup").change(function(){
        var v = $(this).val();
        var reader = new FileReader();
        reader.readAsDataURL(this.files[0]);
        reader.onload = function(e){
            console.log(e.target.result);
            $('#file_base64').val(e.target.result);
        };
    });
});
</script>

上面的表格将发布base64文件块的标头和正文，如下所示。

Header:
Content-Disposition: form-data; name="file_base64"
Body:
data:image/jpg;base64,iVBORw0KGgoAAAANSUhEUgAAB.............

我在 Azure 函数中的 Java 代码：

import java.io.ByteArrayOutputStream;
import java.util.Base64;

if (header.equals("Content-Disposition: form-data; name=\"file_base64\"")) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    multipartStream.readBodyData(baos);
    String content = baos.toString();
    // System.out.println(content);
    int index = content.indexOf(",")+1; // Get the index of base64 string in data-uploaded string
    byte[] imgBytes = Base64.getDecoder().decode(content.substring(index)); // convert image base64 string to image byte arrays
    ....
    // To upload image byte array to Blob Storage
    // You can get the upload image filename from the form input `note`, please notes the order of form input elements.
} else {
    multipartStream.readBodyData(System.out);
}

为什么不用

HttpRequestMessage<Optional<byte[]>> request

代替

HttpRequestMessage<Optional<String>> request

先把身体改造成弦把事情弄糟。