How do I convert a Scala List[org.bson.Document] to a JSON String?

Question

I had a function in AWS Lambda:

def test(pj: Pojo, context: Context): java.util.List[Document]

that was not initializing the pj with the input JSON values at all.

I found another way of doing AWS Lambda in Scala like this:

import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.scala.DefaultScalaModule

val scalaMapper = new ObjectMapper().registerModule(new DefaultScalaModule)

def test(input: InputStream, output: OutputStream): Unit = {
  val inputPojo = scalaMapper.readValue(input, classOf[Pojo])
  val answer: Seq[Document] = getTheRealAnswer(inputPojo)
  val jsonStr = "{ frustration: \"I wish my answer was JSON.\" }"
  output.write(jsonStr.getBytes("UTF-8"))
}

and that works, except what I really want to return as an answer is a JSON array of Documents. How should I go about that?

Edit: In my original posting, I wrote: "[the first example] was returning the answer as an error 22. Basically AWS (I think) treated the JSON conversion of the List[Document] as a filename, JSON has plenty of colons, and the error 22 came from colons in filenames not being allowed. Weird." That turned out to be an error in my invocation of the AWS Lambda Function from AWS CLI. I omitted the output filename in the command invocation, and returned JSON was interpreted by AWS CLI as a filename.

Answer 1

Since I wrote this message, I got things to work like this:

def jsonizeDocs(cDocument: Seq[Document]): String = {
  val sb=new StringBuilder
  for (doc <- cDocument) {
    if (sb.nonEmpty) {
      sb.append(",")
    }
    sb.append(doc.toJson)
  }
  sb.toString
}