I have written a backend servlet to handle the upload of files using the instantUpload feature of sap.m.UploadCollection in Openui5. As I am uploading multiple files to the server, I have chosen the sap.m.UploadCollection instead of the sap.ui.unified.FileUploader. When I try to parse out a list of FileItem instances from the HttpServletRequest in the servlet, it gives me the exception:

" the request doesn't contain a multipart/form-data or multipart/mixed stream "

The ServletFileUpload.isMultipartContent(request) is obviously returning me a false and confirms me that it isn't a multipart/form-data request.

XML Code:

<UploadCollection id="UploadCollection1"
            multiple="true"
            sameFilenameAllowed="true"
            showSeparators="All"
            change="onChangeUploadCollection"
            fileDeleted="onFileDeleted"
            selectionChange="onSelectionChange"
            uploadComplete="onUploadCompleteUploadCollection"
            beforeUploadStarts="onBeforeUploadStarts"
            items="{path : '/record/uploadcollectionitems', 
                   templateShareable : 'true'}"
            uploadUrl="{/record/upload}"
            mode="SingleSelectLeft">

            <toolbar>
                <OverflowToolbar id="myId1">
                    <Title id="attachmentTitle1" />
                    <ToolbarSpacer />
                    <Button id="downloadButton1" text="Download" 
                            press="onDownloadItem"
                            enabled="false" type="Transparent"></Button>
                </OverflowToolbar>
            </toolbar>
            <items>
                <UploadCollectionItem documentId="{documentId}"
                    fileName="{fileName}" mimeType="{mimeType}" 
                    url="{url}" enableEdit="true" enableDelete="true"
                    visibleDelete="true" visibleEdit="true"
                    statuses="{path : '/record/uploadcollectionitems', 
                              templateShareable : 'true'}"
                    selected="false">
                    <statuses>
                        <ObjectStatus title="{Status}" visible="false"
                            state="{state}" icon="{icon}" 
                            iconDensityAware="{iconDensityAware}"
                        textDirection="{textDirection}" />
                    </statuses>
                </UploadCollectionItem>
            </items>
</UploadCollection>

The uploadURL in the XML points to the Servlet, which starts executing after the selection of the file is done on the front-end.

If I choose to use the FileUploader instead of the UploadCollection, it successfully encodes the request as a multipart/form-data, but it does not fulfill my requirements.

I have also tried adding content-typeas a HeaderParameter and setting it to multipart/form-data, in order to make the request as a multipart/form-data. Since such a step is not advisable, I have aborted it mid-way.

Since the sap.m.UploadCollection control uses the sap.ui.unified.FileUploader control and contains dependencies to this control, it is confusing as to why the former would not send the HttpServletRequest as a multipart/form-data.

Note: I have not included the corresponding JavaScript code or the Servlet code for brevity purposes. I'll be happy to include them if required.