org.apache.commons.fileupload.FileUploadBase$InvalidContentTypeException求助

项目本身访问servlet的js代码function submitUpload(){

  usersFunction.getUsernameAndPassword(function(data){
  if(data.length > 3){
  var fromUpload = document.getElementById("fromUpload");
  fromUpload.action=../servlet/addErrorMsg？returnUrl='+'addError.faces';
      fromUpload.method="POST";
      fromUpload.submit();
  }
});
}