How to add a content type to a multipart query without using Blob
I communicate with Salesforce through their REST API via JavaScript. They expect the format of the request body for the multipart / form-data content type to be very specific:
--boundary_string
Content-Disposition: form-data; name="entity_document";
Content-Type: application/json
{
"Description" : "Marketing brochure for Q1 2011",
"Keywords" : "marketing,sales,update",
"FolderId" : "005D0000001GiU7",
"Name" : "Marketing Brochure Q1",
"Type" : "pdf"
}
--boundary_string
Content-Type: application/pdf
Content-Disposition: form-data; name="Body"; filename="2011Q1MktgBrochure.pdf"
Binary data goes here.
--boundary_string--
As seen at https://www.salesforce.com/us/developer/docs/api_rest/Content/dome_sobject_insert_update_blob.htm
In the code below, I got the request body very close to their expected format, except that it does not include the Content-Type (application / json) in the first border.
// Prepare binary data
var byteString = window.atob(objectData.Body);
var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(ab);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
var bb = new Blob([ab], { "type": "image/png" });
// Setup form
var formData = new FormData();
formData.append("entity_attachment", JSON.stringify({ data: '' }));
formData.append("Body", bb);
var request = new XMLHttpRequest();
request.open("POST", myurl);
request.send(formData);
This code will not put the content type for serialized JSON in the first border. It's necessary; in fact, through Fiddler, I was able to confirm that when the Content-Type text exists in the first section of the border, the request handles just fine.
I tried the following, which treats the serialized JSON as bind data, in order to be able to provide a content type:
formData.append("entity_attachment", new Blob([JSON.stringify({ data: '' })], { "type": "application/json"}));
This gives the following HTTP:
Content-Disposition: form-data; name="entity_attachment"; filename="blob"
Content-Type: application/json
...
Unfortunately, the Salesforce server provides the following error message:
Cannot include more than one binary part
The last way I can think of formatting my data in a specific Salesforce body format is to manually create the request body; I tried to do this, but I was embarrassed trying to concatenate the binary, which I'm not sure about how to concatenate the string.
I am looking for any suggestions to get my request body to match Salesforce.
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This answer shows how to manually create a multipart / form request body that includes a binary and bypasses the standard UTF-8 encoding performed by browsers. This is done by passing the entire request as an ArrayBuffer.
Here is the code I am using to solve the problem (see this answer ):
// {
// Body: base64EncodedData,
// ContentType: '',
// Additional attachment info (i.e. ParentId, Name, Description, etc.)
// }
function uploadAttachment (objectData, onSuccess, onError) {
// Define a boundary
var boundary = 'boundary_string_' + Date.now().toString();
var attachmentContentType = !app.isNullOrUndefined(objectData.ContentType) ? objectData.ContentType : 'application/octet-stream';
// Serialize the object, excluding the body, which will be placed in the second partition of the multipart/form-data request
var serializedObject = JSON.stringify(objectData, function (key, value) { return key !== 'Body' ? value : undefined; });
var requestBodyBeginning = '--' + boundary
+ '\r\n'
+ 'Content-Disposition: form-data; name="entity_attachment";'
+ '\r\n'
+ 'Content-Type: application/json'
+ '\r\n\r\n'
+ serializedObject
+ '\r\n\r\n' +
'--' + boundary
+ '\r\n'
+ 'Content-Type: ' + attachmentContentType
+ '\r\n'
+ 'Content-Disposition: form-data; name="Body"; filename="filler"'
+ '\r\n\r\n';
var requestBodyEnd =
'\r\n\r\n'
+ '--' + boundary + '--';
// The atob function will decode a base64-encoded string into a new string with a character for each byte of the binary data.
var byteCharacters = window.atob(objectData.Body);
// Each character code point (charCode) will be the value of the byte.
// We can create an array of byte values by applying .charCodeAt for each character in the string.
var byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
// Convert into a real typed byte array. (Represents an array of 8-bit unsigned integers)
var byteArray = new Uint8Array(byteNumbers);
var totalRequestSize = requestBodyBeginning.length + byteArray.byteLength + requestBodyEnd.length;
var uint8array = new Uint8Array(totalRequestSize);
var i;
// Append the beginning of the request
for (i = 0; i < requestBodyBeginning.length; i++) {
uint8array[i] = requestBodyBeginning.charCodeAt(i) & 0xff;
}
// Append the binary attachment
for (var j = 0; j < byteArray.byteLength; i++, j++) {
uint8array[i] = byteArray[j];
}
// Append the end of the request
for (var j = 0; j < requestBodyEnd.length; i++, j++) {
uint8array[i] = requestBodyEnd.charCodeAt(j) & 0xff;
}
return $j.ajax({
type: "POST",
url: salesforceUrl,
contentType: 'multipart/form-data' + "; boundary=\"" + boundary + "\"",
cache: false,
processData: false,
data: uint8array.buffer,
success: onSuccess,
error: onError,
beforeSend: function (xhr) {
// Setup OAuth headers...
}
});
};
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