我正在尝试向JAVA中的本地服务器发送HTTPPost Multipart请求。我正在尝试发送以下内容：
{
"content-disposition": "form-data; name=\"metadata\"",
"content-type": "application/x-dmas+json",
"body": JSON.stringify(client_req)
},
{
"content-disposition": "attachment; filename=\"" + file + "\"; name=\"file\"",
"content-type": "application/octet-stream",
"body": [file content]
}
我研究了ApacheHTTP组件，但它不允许我为每个部分指定内容类型和配置。以下是我使用ApacheHTTPAPI用JAVA编写的内容：
'CloseableHttpClient httpclient=HttpClient. createDefault（）；
try {
HttpPost httppost = new HttpPost("IP");
FileBody bin = new FileBody(new File(args[0]), "application/octet-stream");
StringBody hash = new StringBody("{\"hash\": \"\", \"policy\": {\"retention_permitted\": true, \"distribution\": \"global\"}}", ContentType.create("application/x-dmas+json"));
HttpEntity reqEntity = MultipartEntityBuilder.create()
.addPart("metadata", hash)
.addPart("file", bin)
.build();
httppost.setEntity(reqEntity);
`
FilePart和StringPart的构造函数参数和方法（您使用它们组成组成多部分请求的Part[]）提供了此信息。
可能为时已晚，但作为寻找同一问题答案的任何人的参考，MultipartEntityBuilder类中有几个方法允许您为每个部分设置内容类型和内容处置。例如，
如果我们在您的示例中使用上述方法，
CloseableHttpClient httpClient = HttpClients.createDefault();
HttpPost uploadFile = new HttpPost("http://url-to-post/");
MultipartEntityBuilder builder = MultipartEntityBuilder.create();
String jsonStr = "{\"hash\": \"\", \"policy\": {\"retention_permitted\": true, \"distribution\": \"global\"}}";
builder.addTextBody("metadata", jsonStr, ContentType.create("application/x-dmas+json"));
builder.addBinaryBody("file", new File("/path/to/file"),
ContentType.APPLICATION_OCTET_STREAM, "filename");
HttpEntity multipart = builder.build();
uploadFile.setEntity(multipart);
HttpResponse response = httpClient.execute(uploadFile);
