Apexでboundary複数でかつファイルを含むmultipartリクエスト

ちょっと汚いけど下記でできる。

    //ファイルの添付
    public static void regFile(String token, String docId) {
        Attachment objPDF = [SELECT id, Body, Name FROM Attachment WHERE id = 'AAAAAAAAAAAA'];

        String endpoint = 'https://XXXXXXXXXXXXXXXXXXXXXXXXX';
        String boundary = String.valueOf(DateTime.now().getTime());

        String strSeparationKey = 'A_RANDOM_STRING';

        String body = '';
        body+='------------' + strSeparationKey + '\n';
        body+='Content-Disposition: form-data; name="test"\n';
        body+='\n';
        body+='aiueo' + '\n';
        body+='------------' + strSeparationKey + '\n';


        // assemble the body payload
        String strHeader = body + '--' + strSeparationKey + '\nContent-Disposition: form-data; name="uploadfile"; filename="' + objPDF.Name + '"\nContent-Type: application/octet-stream\n\n';
        String strBody = EncodingUtil.base64Encode(objPDF.Body);
        String strFooter = '\n--' + strSeparationKey + '--';
        
        String strHeaderEncoded = EncodingUtil.base64Encode(Blob.valueOf(strHeader+'\n'));
        while(strHeaderEncoded.endsWith('=')) {
        strHeader+=' ';
        strHeaderEncoded = EncodingUtil.base64Encode(Blob.valueOf(strHeader+'\n'));
        }
        String strBodyEncoded = strBody;
        String strFooterEncoded = EncodingUtil.base64Encode(Blob.valueOf(strFooter));
        
        Blob blobBody = null;
        String last4Bytes = strBodyEncoded.substring(strBodyEncoded.length()-4,strBodyEncoded.length());
        
        if(last4Bytes.endsWith('=')) {
        Blob decoded4Bytes = EncodingUtil.base64Decode(last4Bytes);
        HttpRequest objHttpRequest = New HttpRequest();
        objHttpRequest.setBodyAsBlob(decoded4Bytes);
        String last4BytesFooter = objHttpRequest.getBody()+strFooter;
        blobBody = EncodingUtil.base64Decode(strHeaderEncoded+strBodyEncoded.substring(0,strBodyEncoded.length()-4)+EncodingUtil.base64Encode(Blob.valueOf(last4BytesFooter)));
        } else {
        blobBody = EncodingUtil.base64Decode(strHeaderEncoded+strBodyEncoded+strFooterEncoded);
        }
        
        if(blobBody.size()>3000000) {
        // throw new CustomException('File size limit is 3 MBytes');
        system.debug('File size limit is 3 MBytes');
        }else{
        system.debug('blobBody.size()'+blobBody.size());
        }
        
        // send out the request
        HttpRequest req = New HttpRequest();
        req.setHeader('Content-Type', 'multipart/form-data; boundary=' + strSeparationKey);
        req.setHeader('Authorization', 'Bearer ' + token);
        req.setMethod('POST');
        req.setEndpoint(endpoint);
        req.setBodyAsBlob(blobBody);
        req.setHeader('Content-Length', String.valueof(req.getBodyAsBlob().size()));
        Http http = New Http();
        HTTPResponse res = http.send(req);
        system.debug('res'+res.getBody());
    }

base64対応だとまだ楽

    public static void regFile(String token, String docId) {
        Attachment atch = [SELECT id, Body FROM Attachment WHERE id = 'AAAAAAAA'];

        String endpoint = 'https://AAAAAAAAAAAAAAAAAAA' + docId + '/files';

        HttpRequest request = new HttpRequest();
        request.setHeader('Authorization', 'Bearer ' + token);
        request.setEndpoint(endpoint);
        request.setMethod('POST');
        request.setHeader('Accept-Language', 'ja');
        request.setHeader('accept', 'application/json');
        
        String boundary = String.valueOf(DateTime.now().getTime());
        String body = '';
        body+='------------' + boundary + '\r\n';
        body+='Content-Disposition: form-data; name="name"\r\n';
        body+='\r\n';
        body+='aiueo' + '\r\n';
        body+='------------' + boundary + '\r\n';
        body+='Content-Disposition: form-data; name="uploadfile"; filename="test.pdf"\r\n';
        body+='Content-Transfer-Encoding: base64\r\n';
        String contentType = 'application/octet-stream';
        body+='Content-Type: ' + contentType + '\r\n\r\n';
        body+=EncodingUtil.base64Encode(atch.body);
        body+='\r\n------------' + boundary + '--';
        request.setHeader('Content-Type', 'multipart/form-data; boundary=----------' + boundary);
        request.setHeader('Content-Length',String.valueof(body.length()));
        request.setBody(body);
        System.debug(request.getBody());
        
        Http http = new Http();
        HttpResponse response = http.send(request);
        response.getBody();


    }