无法将 HashSet 解析为 JSONObject 字符串

Question

I am trying to Convert HashSet<String> to JSONObject and then Parse the output JSON.

Here is what I have tried:

JSONObject json = new JSONObject();
json.put("set", new HashSet<>(Arrays.asList("a", "b")));
json.put("list", Arrays.asList("a", "b"));
String jsonString = json.toJSONString();

System.out.println(jsonString);

JSONParser parser = new JSONParser();
JSONObject afterParse = (JSONObject) parser.parse(jsonString);
System.out.println(afterParse.toJSONString());

But it's giving me this output and error:

{"set":[b, a],"list":["a","b"]}
Exception in thread "main" Unexpected character (b) at position 8.

Here, you can see both a and b are strings, in the list both are inside double quotation marks but in the set it's not.

I am using org.json.simple v1.1.

Answer 1

I think this is a problem with org.json.simple library.

I have used org.json library, and have to do some minor changes in above code to work:

JSONObject json = new JSONObject();
json.put("set", new HashSet<>(Arrays.asList("a", "b")));
json.put("list", Arrays.asList("a", "b"));
String jsonString = json.toString();

System.out.println(jsonString);

JSONObject afterParse = new JSONObject(jsonString);
System.out.println(afterParse.toString());

The output of this code is:

{"set":["a","b"],"list":["a","b"]}

Answer 2

when u convert a array of strings to list and then the list to a Set, it is no longer String, but an array of objects hence new HashSet<>(Arrays.asList("a", "b"))); gives "set":[b, a] (without quotes). And parser.parse(jsonString); works on Object not array of Objects.

Try using a list instead of a set as below :

json.put("set", new Arraylist<>(new HashSet<>(Arrays.asList("a", "b"))));

Answer 3

The alternative solution is use com.fasterxml.jackson.databind.ObjectMapper

   String str = "str1";
   String str2 = "str2";
   String str4 = "str3";

   Set<String> setObject= new HashSet();
   setObject.add(str);
   setObject.add(str2);
   setObject.add(str4);

   ObjectMapper mapperObj = new ObjectMapper();
   String JSON = mapperObj.writeValueAsString(setObject);

Answer 4

You can try this way, here HashSet converts to JsonArray, and now this array put into the JSONObject using any key refer below cup of code.

Set<String> set = new HashSet<>();
set.add("A");
set.add("B");
set.add("C");
set.add("D");

// Conver to JSONArray
JSONArray jsonArray = new JSONArray(set.toArray());

// JSONArray to JSONObject with Key
JSONObject jsonObject = new JSONObject();
jsonObject.put("List", jsonArray);

System.out.println(jsonObject.toString());

// Output:
// {"List":["A","B","C","D"]}