Question

I want to convert an array list to json string of a specific format. I get all the users emails in an array list and want to convert it into the following format of JSON.

 [
  {"email":"[e-mail]"},
  {"email":"[e-mail]"}
 ]

My controller action is

 public static Result apiCustomers(){
    List<Customer> customerList = Model.coll(Customer.class).find().toArray();
    List<String> emails = new ArrayList<String>();

    for(Customer c : customerList){
        emails.add(c.email);
    }

    //ObjectNode result = Json.newObject();
    //result.put("emails", Json.toJson(emails));        
    return ok();
}

How can I convert the emails list to the above json format?

Thanks in advance

Answer 1

Why use another JSON ser/des lib? Play has one built-in (a wrapper around jackson – which is really fast).

Starting from your code:

public static Result apiCustomers(){
    List<Customer> customerList = Model.coll(Customer.class).find().toArray();
    List<String> emails = new ArrayList<String>();

    for(Customer c : customerList){
        emails.add(c.email);
    }

    return ok(Json.toJson(emails));
}

This uses some defaults but should be enough.

Or manually:

public static Result apiCustomers(){
        ArrayNode arrayNode = new ArrayNode(JsonNodeFactory.instance);

        List<Customer> customerList = Model.coll(Customer.class).find().toArray();

        for(Customer c : customerList){
            ObjectNode mail = Json.newObject();
            mail.put("email", c.email);
            arrayNode.add(mail);
        }

        return ok(arrayNode);
}

No need for Gson.