Jackson multiple objects and huge json files

Question

I get the feeling that the answer might be a duplicate of this: Jackson - Json to POJO With Multiple Entries but I think that potentially the question is different enough. Also

Answer 1

Assuming you have an array wrapping your objects, create a JsonParser and then call readValuesAs with the appropriate type. It gives you back an Iterator with all your objects that reads through the file as you consume the objects.

Answer 2

Use this code sample to see the basic idea.

final InputStream in = new FileInputStream("json.json");
try {
  for (Iterator it = new ObjectMapper().readValues(
      new JsonFactory().createJsonParser(in), Map.class); it.hasNext();)
    System.out.println(it.next());
}
finally { in.close();} }

Answer 3

You don't have to choose between Streaming (JsonParser) and ObjectMapper, do both! Traverse a bit with parser, but then call JsonParser.readValueAs(MyType.class) to bind individual JSON Object.

Or, call ObjectMapper's readValue() method passing JsonParser at appropriate points. Or use ObjectMapper.reader(Type.class).readValues() and iterate that way.