import org.json.JSONObject;

import java.util.HashMap;

import java.util.Map;

public class JsonValidator {

public static void validateJson(String jsonString) {

try {

JSONObject jsonObject = new JSONObject(jsonString);

// Define default values for expected fields

Map<String, Object> defaults = new HashMap<>();

defaults.put("name", "Unknown");

defaults.put("age", 0);

defaults.put("city", "DefaultCity");

defaults.put("isActive", false);

// Validate required fields

if (jsonObject.has("name") && jsonObject.get("name") == null) {

System.err.println("Error: 'name' field is missing.");

jsonObject.put("name", defaults.get("name"));

} else if (jsonObject.has("name") && ((String) jsonObject.get("name")).isEmpty()) {

System.err.println("Error: 'name' field is empty.");

jsonObject.put("name", defaults.get("name"));

}

if (jsonObject.has("age") && jsonObject.get("age") == null) {

System.err.println("Error: 'age' field is missing.");

jsonObject.put("age", defaults.get("age"));

} else if (jsonObject.has("age") && !jsonObject.get("age").isNumeric()) {

System.err.println("Error: 'age' field is not a number.");

jsonObject.put("age", defaults.get("age"));

}

if (jsonObject.has("city") && jsonObject.get("city") == null) {

System.err.println("Error: 'city' field is missing.");

jsonObject.put("city", defaults.get("city"));

}

if (jsonObject.has("isActive") && jsonObject.get("isActive") == null) {

System.err.println("Error: 'isActive' field is missing.");

jsonObject.put("isActive", defaults.get("isActive"));

} else if (jsonObject.has("isActive") && !jsonObject.get("isActive").isBoolean()) {

System.err.println("Error: 'isActive' field is not a boolean.");

jsonObject.put("isActive", defaults.get("isActive"));

}

// Print the validated JSON (optional)

System.out.println("Validated JSON: " + jsonObject.toString(2));

} catch (Exception e) {

System.err.println("Error parsing JSON: " + e.getMessage());

System.err.println("Stacktrace: " + e.printStackTrace());

}

}

public static void main(String[] args) {

// Example usage

String json1 = "{\"name\": \"John\", \"age\": 30, \"city\": \"New York\", \"isActive\": true}";

String json2 = "{\"age\": 25, \"city\": \"London\"}";

String json3 = "{\"name\": null, \"age\": \"abc\"}";

String json4 = "{\"name\": \"\", \"age\": 25}";

String json5 = "{\"name\": \"Jane\", \"age\": 28, \"city\": null, \"isActive\": \"yes\"}";

System.out.println("Validating JSON 1:");

validateJson(json1);

System.out.println();

System.out.println("Validating JSON 2:");

validateJson(json2);

System.out.println();

System.out.println("Validating JSON 3:");

validateJson(json3);

System.out.println();

System.out.println("Validating JSON 4:");

validateJson(json4);

System.out.println();

System.out.println("Validating JSON 5:");

validateJson(json5);

System.out.println();

}

}