Java JSONUtils

JSONUtils.java

public class JSONUtils {

    //-------------
    //  DATA
    //-------------

    static public ObjectMapper objectMapper = new ObjectMapper();

    //-------------
    //  METHODS
    //-------------

    static public String object2JSON(Object obj) {
        return object2JSON(obj, false);
    }

    static public String object2JSON(Object obj, boolean pretty) {
        String       json         = null;
        ObjectWriter objectWriter = (pretty) ? objectMapper.writerWithDefaultPrettyPrinter() : objectMapper.writer();

        try {
            json = objectWriter.writeValueAsString(obj);
        }
        catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return json;
    }

    static public Map<String, Object> object2Map(Object obj) {
        Map<String, Object> map = null;

        map = objectMapper.convertValue(obj, Map.class);

        return map;
    }

    static public Map<String, Object> object2Map(Object obj, String... keepFields) {
        Map<String, Object> map = object2Map(obj);

        HashSet<String> keySet = new HashSet<String>(map.keySet());
        keySet.removeAll(new HashSet<String>(Arrays.asList(keepFields)));

        //  /!\  D A N G E R  /!\
        // -> this triggers: java.util.ConcurrentModificationException
//        for (String key : keySet) {
//            map.remove(key);
//        }

        HashSet<String> removeSet = (HashSet<String>) keySet.clone();

        for (String key : removeSet) {
            map.remove(key);
        }

        return map;
    }

    public static void main(String[] args) {
        Email email = new Email();
        email.setId(123);

        System.out.println(JSONUtils.object2Map(email, "id"));
    }
}