A custom Exception which is JSON-like.

CustomException.java

package com.example;

import org.json.JSONObject;

public class ReturnException extends Exception {

	// Because Exception implements Throwable which implements Serializable.
	private static final long serialVersionUID = 1L;

	public ReturnException(){}
	
	// Use Exception constructor with JSON String is from getExceptionJSONString function includes retCode and retMessage.
	public ReturnException(int retCode, String retMessage) {
		super(getExceptionJSONString(retCode, retMessage));
	}
	
 	// Getter of retCode.
	public int getRetCode() {
		// Convert content of exception to be a JSON Object.
		JSONObject jo = new JSONObject(this.getMessage());
		// Get retCode of the JSON Object as an integer and return.
		return jo.getInt("retCode");
	}
	
 	// Getter of retMessage.
	public String getRetMessage() {
		JSONObject jo = new JSONObject(this.getMessage());
		return jo.getString("retMessage");
	}
	
 	// For constructor.
	private static String getExceptionJSONString(int retCode, String retMessage) {
		JSONObject jo = new JSONObject();
		jo.put("retCode", retCode);
		jo.put("retMessage", retMessage);
		return jo.toString();
	}
	
}