Add a mechanism for writing sequences of values via `ObjectWriter.writeValues()`

[cowtowncoder]

It has been possible to read value sequences with ObjectReader.readValues() for a while; this is especially useful for formats like CSV that are basically sequences of more or less uniform values.
But there is no similar mechanism for writing, so developers have to construct JsonGenerator directly first, then use ObjectMapper (or ObjectWriter) on that. This is cumbersome.

It would make sense to add a new sequence writer abstraction, accessible via ObjectWriter; method could be named ObjectWriter.writeValues().

[mjball]

Thanks for adding this – I'll be using it as soon as it's released :)

[l15k4]

Hey, is it possible to choose separator? It uses space separator by default, I would need EOL separator.

I tried writer.withRootValueSeparator("\n") but that's not it. It seems to be separating the Collection by \n but the individual elements of the Collection are space separated, so that if you write multiple times to a single file it leads to weird combined delimiting by \n and space

@cowtowncoder It is weird though because based on the documentation :

Caller may want to override so-called "root value separator",
String added (verbatim, with no quoting or escaping) between
values in root context. Default value is a single space character,
but this is often changed to linefeed.

It should be it, right? I'm using :

"com.fasterxml.jackson.module" %% "jackson-module-scala" % "2.6.3"

Code :

object ObjMapper extends ObjectMapper with ScalaObjectMapper {
  setSerializationInclusion(JsonInclude.Include.NON_NULL)
  registerModule(DefaultScalaModule)
  val prettyWriter = writer(new DefaultPrettyPrinter)
  val miniWriter = writer(new MinimalPrettyPrinter)
}
def writeJson(file: File, recs: Seq[Rec]) = {
    import scala.collection.JavaConverters._
    var writer: SequenceWriter = null
    try {
      writer =
        ObjMapper
          .miniWriter
          .withRootValueSeparator("\n")
          .writeValues(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file, true), StandardCharsets.UTF_8), 32768))
          .writeAll(recs.asJava)
    } finally Option(writer).foreach(_.close())
}

And this is the result if you write sequence twice into a file:

{"1":1} {"2":2} {"3":3}{"1":1} {"2":2} {"3":3}

[l15k4]

Got it, it was the MinimalPrettyPrinter. It somehow doesn't allow for the withRootValueSeparator("\n") to take effect...