.MultipartStream$MalformedStreamException: Stream ended unexpectedly

When uploading files using the browser,it does not happen.But when submission using tools with 'multipart/form-data',for example httpclient,advanced rest client and so on,
Only submit a text field, file field is empty, it will report the following exception:

org.apache.commons.fileupload.MultipartStream$MalformedStreamException: Stream ended unexpectedly
at org.apache.commons.fileupload.MultipartStream.readHeaders(MultipartStream.java:540)
at org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.findNextItem(FileUploadBase.java:1038)
at org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.<init>(FileUploadBase.java:1003)
at org.apache.commons.fileupload.FileUploadBase.getItemIterator(FileUploadBase.java:310)
at org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:334)
at org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java:115)

A simple analysis that, when using the browser, file is not selected, the default browser will join the empty data file-part.
But the use of tools such as httpclient, when the file is empty, it do not contain the documents data.