一、multipart/mixed 請求
multipart/mixed 和 multipart/form-date 都是多檔案上傳的格式。差別在于：multipart/form-data 是一種特殊的表單上傳，其中普通字段的内容還是按照一般的請求體建構，檔案字段的内容按照 multipart 請求體建構，後端在處理 multipart/form-data 請求的時候，會在伺服器上建立臨時的檔案夾存放檔案内容，可參看這篇文章；而 multipart/mixed 請求會将每個字段的内容，不管是普通字段還是檔案字段，都變成 Stream 流的方式去上傳，是以後端在處理 multipart/mixed 的内容時，必須從 Stream 流中讀取。
二、HttpServletRequest 處理 multipart/mixed 請求
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
Part signPart = request.getPart(Constants.SIGN_KEY);
Part appidPart = request.getPart(Constants.APPID_KEY);
Part noncestrPart = request.getPart(Constants.NONCESTR_KEY);
Map<String, String[]> paramMap = new HashMap<>(8);
paramMap.put(signPart.getName(), new String[]{stream2Str(signPart.getInputStream())});
paramMap.put(appidPart.getName(), new String[]{stream2Str(appidPart.getInputStream())});
paramMap.put(noncestrPart.getName(), new String[]{stream2Str(noncestrPart.getInputStream())});
// 其他處理
}
private String stream2Str(InputStream inputStream) {
try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"))) {
String line;
StringBuilder builder = new StringBuilder();
while ((line = reader.readLine()) != null) {
builder.append(line);
}
return builder.toString();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return "";
}
三、SpringMVC 處理 multipart/mixed 請求
SpringMVC 可以直接以 @RequestPart 注解接收 multipart/mixed 格式的請求參數。
@ResponseBody
@RequestMapping(value = {"/token/user/uploadImage"}, method = {RequestMethod.POST, RequestMethod.GET})
public AjaxList uploadImage(
@RequestPart (required = false) String token,
@RequestPart (required = false) String sign,
@RequestPart (required = false) String appid,
@RequestPart (required = false) String noncestr,
@RequestPart MultipartFile file, HttpServletRequest request) {
}