Working with JSON streams efficiently (in Java)

Question

I've been using both JSONObject and JSONReader, but ideally I'm looking for a hybrid :)

In particular, given a stream of JSON objects, part of arbitrarily long JSON array, is there a helper/library that yields "JSONObject" at a time, iterator style, instead of reading everything in or having to parse out individual primitive fields (JsonReader)?

Example of hypothetical API:

JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8"));

reader.beginArray();
while (reader.hasNext()) 
{
  JSONObject obj = reader.readObject();
  // do something with 'obj'
}
reader.endArray();

Above, calling readObject parses some complex JSON sub-tree and returns it as JSONObject.

Answer 1

There's the javax.json.JSONParser.

An example that prints out a JSON:

import javax.json.Json;
import javax.json.stream.JsonParser;
...
JsonParser parser = Json.createParser(new StringReader(jsonData));
while (parser.hasNext()) {
   JsonParser.Event event = parser.next();
   switch(event) {
      case START_ARRAY:
      case END_ARRAY:
      case START_OBJECT:
      case END_OBJECT:
      case VALUE_FALSE:
      case VALUE_NULL:
      case VALUE_TRUE:
         System.out.println(event.toString());
         break;
      case KEY_NAME:
         System.out.print(event.toString() + " " +
                          parser.getString() + " - ");
         break;
      case VALUE_STRING:
      case VALUE_NUMBER:
         System.out.println(event.toString() + " " +
                            parser.getString());
         break;
   }
}

from The Java EE Tutorial 19.4.1 Reading JSON Data Using a Parser. It's part of the JavaEE 7 API but a standalone jar can be gotten from https://jsonp.java.net/download.html.