Using CommonsMultipartResolver to parse an HTTP request with embedded multipart content - spring

Question

I am using Spring Integration to receive an HTTP request which has multipart content nested inside a multipart request as shown below. When using CommonsMultipartResolver as the resolver the LinkedMultiValueMap passed to the receiving service activator contains a map of all the parts but the imbedded multipart is an UploadedMultipartFile which contains the entire content. In the sample boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL is the boundary of the embedded multipart.
How can I get the embedded multipart parsed into a LinkedMultiValueMap so that I can get the version and payload? Is it possible for the CommonsMultipartResolver to do this or is there another way to parse it?
Http Request:
POST http://xxxxx:8087/edi846Inbound HTTP/1.1
Content-Type: multipart/form-data;boundary=DM1-Sb0636VXPQNO3412Ygegb9suqr
.......
Content-Length: 2787
--DM1-Sb0636VXPQNO3412Ygegb9suqr
Content-Disposition: form-data; name="from"
Content-Type: text/plain;charset=ISO-8859-1 Content-Length: 7
gisb-acknowledgement-receipt
--DM1-Sb0636VXPQNO3412Ygegb9suqr
Content-Disposition: form-data; name="input-format" Content-Type:
text/plain;charset=ISO-8859-1 Content-Length: 3
X12
--DM1-Sb0636VXPQNO3412Ygegb9suqr
Content-Disposition: form-data; name="input-data"; filename="TEST-DTEBS_846_3563_10142015102600.x12"
Content-Type:
multipart/encrypted;boundary=boundary2--extKDvsqGExTQI2WVuplHFCUQJ3XVL protocol:
application/pgp-encrypted
boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL
Content-Disposition: form-data; name="version" Content-Type:
application/pgp-encrypted Content-Length: 10
Version: 1
boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL
Content-Disposition: form-data; name="payload" Content-Type: application/octet-stream Content-Length:
1118
-----BEGIN PGP MESSAGE----- Version: BCPG v1.47
hQIOA8aa0/bci2e/EAf/fkgOBK+cOoeY+44htcvjE9Sxk9RK73aOEaxDOBNqFOsV
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PnoJVTrxUd3b2WKgR4FZB+imYRWEz5KLnB5ZVedC+fU24bECcNptrTQaZZUWnR3Z
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ljlZFD6e7PJfjo/RIhb0zMvtBvRTONRrMXKRdRY=
=serM
-----END PGP MESSAGE-----
boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL--
--DM1-Sb0636VXPQNO3412Ygegb9suqr--
Embedded content from Map:
boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL
Content-Disposition: form-data; name="version" Content-Type: application/pgp-encrypted Content-Length:
10
Version: 1
boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL
Content-Disposition: form-data; name="payload" Content-Type: application/octet-stream Content-Length:
1118
-----BEGIN PGP MESSAGE----- Version: BCPG v1.47
hQIOA8aa0/bci2e/EAf/fkgOBK+cOoeY+44htcvjE9Sxk9RK73aOEaxDOBNqFOsV
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ljlZFD6e7PJfjo/RIhb0zMvtBvRTONRrMXKRdRY=
=serM
-----END PGP MESSAGE-----
boundary2----extKDvsqGExTQI2WVuplHFCUQJ3XVL--

Answer 1

Not sure what you mean, but I'd suggest to DEBUG the code in the MultipartAwareFormHttpMessageConverter.readMultipart(). That is a place where an UploadedMultipartFile appears.

Answer 2

A quick look at the CommonsMultipartResolver seems to indicate it doesn't support nested multiparts.
It might not be too hard to subclass it and override parseRequest(), but you might have to dig into commons-fileupload as well.
EDIT
Regarding multipart response:
I just patched the http sample and found that, as long as the request has a proper accept header, simply returning a MultiValueMap "just works".
If you need more control over the part headers, you would need to subclass the AllEncompassingFormHttpMessageConverter and override getHttpEntity() to insert extra headers and configure the gateway to use the custom adapter. Basic headers work ok, though - this...
MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
map.add("foo", "Hello");
map.add("bar", "baz");
map.add("fiz", "qux".getBytes());
return map;
...results in this...
--6_zk8PXoaiUO_By2XJuUpjs5CEEnYM-wj0qE
Content-Disposition: form-data; name="foo"
Content-Type: text/plain;charset=ISO-8859-1
Content-Length: 5
Hello
--6_zk8PXoaiUO_By2XJuUpjs5CEEnYM-wj0qE
Content-Disposition: form-data; name="bar"
Content-Type: text/plain;charset=ISO-8859-1
Content-Length: 3
baz
--6_zk8PXoaiUO_By2XJuUpjs5CEEnYM-wj0qE
Content-Disposition: form-data; name="fiz"
Content-Type: application/octet-stream
Content-Length: 3
qux
--6_zk8PXoaiUO_By2XJuUpjs5CEEnYM-wj0qE--