How to map json from java object dynamically?

Question

How can we map the java object to json? Java object will have a map and some other string properties. What I want is that when we convert the java object to json that map keys should be as root key not nested key.

Sample Java Object :

class Demo {
    String name;
    String designation;
    Map<String,Object> attribute;
}

Now if Map is having values like below :

Map<String,Object> attribute = new HashMap<>();
attribute.put("score",190);
attribute.put("status","allowed");

Output should be like below:

{
  "name":"jack",
  "designation":"Tester",
  "score":190,
  "status":"allowed"
}

Answer 1

If I get you right - use Jackson. Example:

Java Objects to JSON

ObjectMapper mapper = new ObjectMapper();

// Java object to JSON file
mapper.writeValue(new File("c:\\test\\staff.json"), new Staff());

// Java object to JSON string
String jsonString = mapper.writeValueAsString(object);

JSON to Java Objects

ObjectMapper mapper = new ObjectMapper();

//JSON file to Java object
Staff obj = mapper.readValue(new File("c:\\test\\staff.json"), Staff.class);

//JSON URL to Java object
Staff obj = mapper.readValue(new URL("http://some-domains/api/name.json"), Staff.class);

//JSON string to Java Object
Staff obj = mapper.readValue("{'name' : 'mkyong'}", Staff.class);

Repo: https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind

Jackson JSON Tutorial: https://www.baeldung.com/jackson

Another example: https://mkyong.com/java/jackson-2-convert-java-object-to-from-json/