hashmap - Map<String, HashSet<String>> to JSON, & Pretty Print

Question

I'm trying to make my dataset correspond to this example:

var family = [{
    "name" : "Jason",
    "age" : "24",
    "gender" : "male"
},
{
    "name" : "Kyle",
    "age" : "21",
    "gender" : "male"
}];

I have a Map<String, HashSet<String>> of Names and unique alpha-numeric values correponding to specific entities to which those names could refer, let's call these entry items "IDs".

So for instance, Fyodor Mikhailovich Dostoyevsky would perhaps be related to the ID Q626, because that's a very specific reference, there aren't many widely known figures with that name. Whereas, Bush might be attached to G027, Q290, and Q118, referencing perhaps the man, the beer, and the shrub, in no particular order.

It looks like this (the real one is much bigger):

[Rao=[Q7293658, , Q7293657, Q12953055, Q3531237, Q4178159, Q1138810, Q579515, Q3365064, Q7293664, Q1133815], Hani Durzy=[], Louise=[, Q1660645, Q130413, Q3215140, Q152779, Q233203, Q7871343, Q232402, Q82547, Q286488, Q156723, Q3263649, Q456386, Q233192, Q14714149, Q12125864, Q57669, Q168667, Q141410, Q166028], Reyna=[Q7573462, Q2892895, Q363257, Q151944, Q3740321, Q2857439, Q1453358, Q7319529, Q733716, Q16151941, Q7159448, Q5484172, Q6074271, Q1753185, Q7319532, Q5171205, Q3183869, Q1818527, Q251862, Q3840414, Q5271282, Q5606181]]

---

Using Jackson I tried like this:

Map<String, HashSet<String>>  map = q_valMap;
mapper.writeValue(new File("JSON_Output/user.json"), map);

But this seems wrong, as my output was all jumbled together, i.e.

{"Rao":["Q7293658","","Q7293657","Q12953055","Q3531237","Q4178159","Q1138810","Q579515","Q3365064","Q7293664","Q1133815"],"Hani Durzy":[""],"Louise":["","Q1660645","Q130413","Q3215140","Q152779","Q233203","Q7871343","Q232402","Q82547","Q286488","Q156723","Q3263649","Q456386","Q233192","Q14714149","Q12125864","Q57669","Q168667","Q141410","Q166028"],"Reyna":["Q7573462","Q2892895","Q363257","Q151944","Q3740321","Q2857439","Q1453358","Q7319529","Q733716","Q16151941","Q7159448","Q5484172","Q6074271","Q1753185","Q7319532","Q5171205","Q3183869","Q1818527","Q251862","Q3840414","Q5271282","Q5606181"]}

Do I just have to populate this JSON object iteratively?

---

Like the example up top, I think it should look something like this, though what follows is only a pseudocodish characterization, which is to say, not exactly this but something similar:

{
    key: "Rao"
    value:  ["Q7293658","","Q7293657","Q12953055","Q3531237","Q4178159","Q1138810","Q579515","Q3365064","Q7293664","Q1133815"]

    key: "Hani Durzy"
    value: [""]

    key: "Louise"
    value: ["","Q1660645","Q130413","Q3215140","Q152779","Q233203","Q7871343","Q232402","Q82547","Q286488","Q156723","Q3263649","Q456386","Q233192","Q14714149","Q12125864","Q57669","Q168667","Q141410","Q166028"]

    key: "Reyna"
    value: ["Q7573462","Q2892895","Q363257","Q151944","Q3740321","Q2857439","Q1453358","Q7319529","Q733716","Q16151941","Q7159448","Q5484172","Q6074271","Q1753185","Q7319532","Q5171205","Q3183869","Q1818527","Q251862","Q3840414","Q5271282","Q5606181"]
}

is that not right?

---

UPDATE

public class JsonMapFileExample 
{
    public static void map(Map<String, HashSet<String>> q_valMap ) 
    {

        ObjectMapper mapper = new ObjectMapper();


        ArrayNode array = mapper.createArrayNode();
        for ( Entry entry: q_valMap.entrySet() ) 
        {
          ObjectNode node = mapper.createObjectNode()
              .put("name", entry.getKey())
              .put("ids", entry.getValue());
          array.add(node);
        }
        mapper.writeValue("/home/matthias/Workbench/SUTD/nytimes_corpus/wdtk-parent/wdtk-examples/JSON_Output/user.json", array);

    }
}


class MyEntity
{
    private String name;
    Set<String> value; // use names that you want in the result JSON

    //constructors
    public MyEntity() 
    {

    }
    public MyEntity(String name) 
    {
        this.name = name;
    }

    //getters
    public String getName() 
    {
        return this.name;
    }
    public Set<String>  getValue() 
    {
        return this.value;
    }

    //setters
    public void setName(String name) 
    {
        this.name = name;
    }
    public void setValue(Set<String> value) 
    {
        this.value = value;
    }
}

Answer 1

You could manually set the key names, something like:

ArrayNode array = mapper.createArrayNode();
for (Entry entry: yourMap.entries()) {
  ObjectNode node = mapper.createObjectNode()
      .put("name", entry.key())
      .putPOJO("ids", entry.value());
  array.add(node);
}
mapper.writeValue(file, array);

Alternatively, you could create a class for your data

class MyEntity {
  String name;
  Set<String> ids; // use names that you want in the JSON result
  // getters, setters if necessary
}

Transform your data map into a list of MyEntity, then use Jackson ObjectMapper to create JSON like mapper.writeValue(file, listOfMyEntities), the output would be like

[
  {
    "name": "some name here",
    "ids": ["id1", "id2", ...]  
  }
  // more elements here
]