Android: trying to create a JSON file from SQLite database entries

Question

So I am trying to pull data from my database and essentially create a JSON file that looks like this. I know of that I can use my_json_object.put(); but that seems to only work for String, String. I and I want to create the value with 2 entries, and the second entryw ill actually be an array of many values. How can I achieve that? Thanks guys.

{"value": {
"name": "History",
"values": [ 
{"front": "History Market", "back": " It is the world of the world that the world    could not say that", "color": "Yellow"},
{"front": "History Market", "back": " It is the world of the world that the world could not say that", "color": "Red"},
{"front": "History Market", "back": " It is the world of the world that the world could not say that", "color": "Purple"},
{"front": "History Market", "back": " It is the world of the world that the world could not say that", "color": "Blue"},
{"front": "History Market", "back": " It is the world of the world that the world could not say that", "color": "Blue"}
]}}

Construct the desired "nest" of arrays and dictionaries/maps and use a JSON serializer to create the JSON string. — Hot Licks
– Hot Licks, Commented Jan 26, 2013 at 19:52

ρяσѕρєя K · Accepted Answer · 2013-01-26 20:03:52Z

4

Create your current jsonObject as :

//Create main json object
JSONObject json = new JSONObject();

//Create value json object
JSONObject valueJson = new JSONObject();

//Create values JSONArray
JSONArray valuesarray = new JSONArray();

for(int i=0;i<=4;i++){
 // Create values jsonObject
JSONObject valuesJson = new JSONObject();
valuesJson.put("front","front_value");
valuesJson.put("back","back_value");
valuesJson.put("color","color_value");
 // put values jsonObject to valuesarray JSONArray
valuesarray.put(valuesJson);    

}
 // put name key-value to value jsonObject
valueJson.put("name","History");
 // put values JSONArray to value jsonObject
valueJson.put("values",valuesarray);

 // put value jsonObject to final json Object
json.put("value",valueJson);

answered Jan 26, 2013 at 20:03

ρяσѕρєя K

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Comments

Georgy Gobozov · Accepted Answer · 2013-01-26 20:08:27Z

Use google gson, it is very simple and ferfectly works with arrays and lists

public class CollectionToJson {
public static void main(String[] args) {
    //
    // Converts a collection of string object into JSON string.
    //
    List<String> names = new ArrayList<String>();
    names.add("Alice");
    names.add("Bob");
    names.add("Carol");
    names.add("Mallory");

    Gson gson = new Gson();
    String jsonNames = gson.toJson(names);
    System.out.println("jsonNames = " + jsonNames);

    //
    // Converts a collection Student object into JSON string
    //
    Student a = new Student("Alice", "Apple St",
            CollectionToJson.getDOB(2000, 10, 1));
    Student b = new Student("Bob", "Banana St", null);
    Student c = new Student("Carol", "Grape St",
            CollectionToJson.getDOB(2000, 5, 21));
    Student d = new Student("Mallory", "Mango St", null);

    List<Student> students = new ArrayList<Student>();
    students.add(a);
    students.add(b);
    students.add(c);
    students.add(d);

    gson = new Gson();
    String jsonStudents = gson.toJson(students);
    System.out.println("jsonStudents = " + jsonStudents);

    //
    // Converts JSON string into a collection of Student object.
    //
    Type type = new TypeToken<List<Student>>(){}.getType();
    List<Student> studentList = gson.fromJson(jsonStudents, type);

    for (Student student : studentList) {
        System.out.println("student.getName() = " + student.getName());
    }
}

private static Date getDOB(int year, int month, int date) {
    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.YEAR, year);
    calendar.set(Calendar.MONTH, month - 1);
    calendar.set(Calendar.DATE, date);
    calendar.set(Calendar.HOUR, 0);
    calendar.set(Calendar.MINUTE, 0);
    calendar.set(Calendar.SECOND, 0);
    return calendar.getTime();
}

}

Output

 jsonNames = ["Alice","Bob","Carol","Mallory"]
jsonStudents = [{"name":"Alice","address":"Apple St","dateOfBirth":"Nov 1, 3900 12:00:00 AM"},{"name":"Bob","address":"Banana St"},{"name":"Carol","address":"Grape St","dateOfBirth":"Jun 21, 3900 12:00:00 AM"},{"name":"Mallory","address":"Mango St"}]
student.getName() = Alice
student.getName() = Bob
student.getName() = Carol
student.getName() = Mallory

thanks for your answer also. I chose the answer above becuase I did't want to use a library. I am sure it works perfectly though.

Mr.Me · Accepted Answer · 2013-01-26 20:05:52Z

0

JSONObject can have JSONArray nested inside it and visa versa .

in your example you will have to create :

List item
JSONObject
inside it a JSONObject called "value"
Inside it a String entry called "name" with a String value "History".
And a JSONArray entry.
List item
Inside that JSONArray a set of JSONObjects.

answered Jan 26, 2013 at 20:05

Mr.Me

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