Java : Sort JSON String using key

Question

I have a String which is in JSON format. I need to sort this JSON string using attributes but am unable to do it. JSON String is created by reading a CSV file. I do not want to read the CSV again and have to implement it using JSON String only. Is there a way to do that? Please let me know.

JSON String format is :

[
  {
    "address": "some address",
    "name": "some name",
    "phone": "some phone",
    "age": "some age",
    "SSN": "some SSN"
  },
  {
    "address": "abc",
    "name": "def",
    "phone": "ghi",
    "age": "jkl",
    "SSN": "mno"
  }
]

Please explain.

you mean "sort this JSON string using attributes" as e.g. to sort the above entries in alphabetical order by address? — hammerfest
– hammerfest, Commented Oct 12, 2016 at 7:42

poozmak · Accepted Answer · 2016-10-12 08:05:25Z

You can convert the JSONstring into a TreeMap with a Comparator you implement to compare by value, and then convert this TreeMap back to JSON.

See how to create a value Comparator here: http://www.programcreek.com/2013/03/java-sort-map-by-value/

And then use ObjectMapper to convert the JSON into a map the the map back to JSON:

String json = "{\"address\" : \"def\","
    + "\"name\" : \"ghi\","
    + "\"phone\" : \"jkl\","
    + "\"age\" : \"def\","
    + "\"SSN\" : \"abc\"}";

Map<String, String> jsonMap = new HashMap<String, String>();
ObjectMapper mapper = new ObjectMapper();
jsonMap = (mapper.readValue(json, Map.class));
Comparator<String> comparator = new ValueComparator(jsonMap);
Map<String, String> treeMap = new TreeMap<String, String>(comparator); 
treeMap.putAll(jsonMap);
String sortedJson = mapper.writeValueAsString(treeMap);

System.out.println(sortedJson);

Result: {"SSN":"abc","address":"def","name":"ghi","phone":"jkl"}

Comparator:

public class ValueComparator implements Comparator<String> {

   Map<String, String> map = new HashMap<String, String>();

   public ValueComparator(Map<String, String> map){
     this.map = map;
   }

   @Override
   public int compare(String s1, String s2) {
     return map.get(s1).compareTo(map.get(s2));
   }
 }

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