ESB v6.5.1，使用问题（error:the request was rejected because no multipart boundary was found）

【问题描述】

外网有个表单，需要调用内网ESB的服务。表单上需要上传附件，已经在form上增加了enctype="multipart/form-data"，直接调用后台服务时，代码运行正确。但经过ESB穿透时，出现如下问题：error:the request was rejected because no multipart boundary was found。代码上已经增加了connection.setRequestProperty("Content-Type","multipart/form-data; boundary=" + BOUNDARY);