[Salesforce]ApexでREST API使用して画像ファイルUpload

ApexでREST API使用して画像ファイルUpload

    public void fileUpload(Attachment attach){


        HttpRequest req = new HttpRequest();
        Http http = new Http();
        HTTPResponse res = new HTTPResponse();

        String boundary = '------------' + String.valueOf(DateTime.now().getTime());

        String header += '--' + boundary;
        header += '\r\n';
        header += 'Content-Disposition: form-data; name="attach"; filename="' + attach.name + '"';
        header += '\r\n';
        header += 'Content-Type: ' + attach.ContentType;
        String headerEncoded = EncodingUtil.base64Encode(Blob.valueOf(header+'\r\n\r\n'));
        while(headerEncoded.endsWith('=')){
            header += ' ';
            headerEncoded = EncodingUtil.base64Encode(Blob.valueOf(header + ' ' +'\r\n\r\n'));
        }

        String bodyEncoded = EncodingUtil.base64Encode(attach.Body);

        String footor += '\r\n';
        footor += '--'+boundary;
        footor += '\r\n';
        footor += 'Content-Disposition: form-data; name="attachname"';
        footor += '\r\n\r\n';
        footor += attach.name;
        footor += '\r\n';
        footor += '--'+boundary+'--';             
        String footorEncoded = EncodingUtil.base64Encode(Blob.valueOf(footor));

        Blob bodyBlob = null;
        String last4Bytes = bodyEncoded.substring(bodyEncoded.length()-4,bodyEncoded.length());
        if(last4Bytes.endsWith('='))
        {
                Blob decoded4Bytes = EncodingUtil.base64Decode(last4Bytes);
                HttpRequest tmp = new HttpRequest();
                tmp.setBodyAsBlob(decoded4Bytes);
                String last4Bytesfootor = tmp.getBody()+footor;   
                bodyBlob = EncodingUtil.base64Decode(headerEncoded+bodyEncoded.substring(0,bodyEncoded.length()-4)+EncodingUtil.base64Encode(Blob.valueOf(last4Bytesfootor)));
        }
        else
        {
                bodyBlob = EncodingUtil.base64Decode(headerEncoded+bodyEncoded+footorEncoded);
        }

        req = new HttpRequest();
        req.setHeader('Content-Type','multipart/form-data; boundary=' + boundary);
        req.setMethod('POST');
        req.setEndpoint('https://' + endPoint);
        req.setBodyAsBlob(bodyBlob);
        req.setTimeout(120000);
    
        http = new Http();
        res = http.send(req);

    }