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797da24 Sep 14, 2016
102 lines (87 sloc) 3.3 KB
public class HttpFormBuilder {
// The boundary is alligned so it doesn't produce padding characters when base64 encoded.
private final static string Boundary = '1ff13444ed8140c7a32fc4e6451aa76d';
/**
* Returns the request's content type for multipart/form-data requests.
*/
public static string GetContentType() {
return 'multipart/form-data; charset="UTF-8"; boundary="' + Boundary + '"';
}
/**
* Pad the value with spaces until the base64 encoding is no longer padded.
*/
private static string SafelyPad(
string value,
string valueCrLf64,
string lineBreaks) {
string valueCrLf = '';
blob valueCrLfBlob = null;
while (valueCrLf64.endsWith('=')) {
value += ' ';
valueCrLf = value + lineBreaks;
valueCrLfBlob = blob.valueOf(valueCrLf);
valueCrLf64 = EncodingUtil.base64Encode(valueCrLfBlob);
}
return valueCrLf64;
}
/**
* Write a boundary between parameters to the form's body.
*/
public static string WriteBoundary() {
string value = '--' + Boundary + '\r\n';
blob valueBlob = blob.valueOf(value);
return EncodingUtil.base64Encode(valueBlob);
}
/**
* Write a boundary at the end of the form's body.
*/
public static string WriteBoundary(
EndingType ending) {
string value = '';
if (ending == EndingType.Cr) {
// The file's base64 was padded with a single '=',
// so it was replaced with '\r'. Now we have to
// prepend the boundary with '\n' to complete
// the line break.
value += '\n';
} else if (ending == EndingType.None) {
// The file's base64 was not padded at all,
// so we have to prepend the boundary with
// '\r\n' to create the line break.
value += '\r\n';
}
// Else:
// The file's base64 was padded with a double '=',
// so they were replaced with '\r\n'. We don't have to
// do anything to the boundary because there's a complete
// line break before it.
value += '--' + Boundary + '--';
blob valueBlob = blob.valueOf(value);
return EncodingUtil.base64Encode(valueBlob);
}
/**
* Write a key-value pair to the form's body.
*/
public static string WriteBodyParameter(
string key,
string value) {
string contentDisposition = 'Content-Disposition: form-data; name="' + key + '"';
string contentDispositionCrLf = contentDisposition + '\r\n\r\n';
blob contentDispositionCrLfBlob = blob.valueOf(contentDispositionCrLf);
string contentDispositionCrLf64 = EncodingUtil.base64Encode(contentDispositionCrLfBlob);
string content = SafelyPad(contentDisposition, contentDispositionCrLf64, '\r\n\r\n');
string valueCrLf = value + '\r\n';
blob valueCrLfBlob = blob.valueOf(valueCrLf);
string valueCrLf64 = EncodingUtil.base64Encode(valueCrLfBlob);
content += SafelyPad(value, valueCrLf64, '\r\n');
return content;
}
/**
* Helper enum indicating how a file's base64 padding was replaced.
*/
public enum EndingType {
Cr,
CrLf,
None
}
}