How to post attachments using form to agent

I have a form with some text fields and I also needed to send attachments within same form.

Form is printed by agent and is processed by another agent written in LotusScript.

I spent some time working on solution and here it is.

The idea is to convert selected files to base64 on client side and then post data on submission and agent that process submission will conver base64 to file.

Here is a form, note that we run some logic when files are added

<form name="formName" method="post" action="agentName?openagent">
<input name="title" value="xxx">
<input type="file" name="files" multiple onchange="toBase64()">
</form>

Here is how we convert selected files to base64 and how we results as text fields to form (JS is not optimal, it can be done without jQuery)

function toBase64() {
  var files = document.querySelector('input[type=file]').files;

  var form = $("form");
  form.find("input[name^='filebase64']").remove(); // replace

  function readAndSave(file, index) {
    var reader = new FileReader();
	
    reader.addEventListener("load", function() {
      form.append("");
      form.append("");
    }, false);

    reader.readAsDataURL(file);
  }

  if (files) {
    [].forEach.call(files, readAndSave);
  }
}

Once form is submitted we have to read base64 items and convert them to file. There are at least 2 solutions: pure LS or Java/LS2J

a) LotusScript using NotesMIMEHeader

Private Function saveBase64AsFile(base64 As String, filePath As string) As Boolean
	On Error GoTo ErrorHandler

	Dim stub As NotesDocument
	Dim stream As NotesStream
	Dim item As NotesMIMEEntity
	Dim header As NotesMIMEHeader
	Dim emb As NotesEmbeddedObject
	Dim fileName As String
	Dim contentType As string
	Dim base64File As String

	fileName = StrRightBack(filePath, "\")
	contentType = StrRight(Strleft(base64, ";"), ":")
	base64File = StrRight(Base64, ",")
	
	Call scriptLog.loginfo(fileName)
	Call scriptLog.loginfo(contentType)
	
	Set stub = db.Createdocument()
	Set item = stub.CreateMIMEEntity("Body")
	Set header = item.createHeader("Content-Disposition")
	Call header.setHeaderVal({attachment; filename="} & fileName & {"})

	Set stream = app.NotesSession.CreateStream()
	Call stream.WriteText(base64File)
	Call item.SetContentFromText(stream, contentType, ENC_BASE64)

	Call stream.Truncate
	Call stream.Close
	Call stub.Closemimeentities(True)

	Set emb = stub.Getattachment(fileName)
	Call emb.Extractfile(filePath)
	
	Exit Function
ErrorHandler:
	Error Err, Error
End Function

b) Java with LS2J using native classses.

import java.util.Base64;
import java.io.IOException;
import java.nio.file.*;

public class Base64ToFile{

	public boolean convert(String base64String, String filePath) {
		try {
			byte[] decodedImg = Base64.getDecoder().decode(base64String.getBytes());
			Path destinationFile = Paths.get(filePath);
			Files.write(destinationFile, decodedImg);
			return true;
		} catch (IOException e) {
			e.printStackTrace();
		}
		return false;
	}
}

UseLSX "*javacon"
Use "Base64ToFile"

Class Base64ToFile
	Private jSession As JavaSession
	Private jClass As Javaclass
	Private jObject As JavaObject
	Private jError As JavaError
	
	Sub New()
		Set jSession = New JavaSession
		Set jClass = jSession.GetClass("Base64ToFile")
		Set jObject = jClass.Createobject()
	End Sub
	
	Public Function convert(base64 As String, filePath As String) As Boolean
		convert = jObject.convert(base64, filePath)
	End Function
End Class