package lesson6.json;
import lesson6.json.adapters.JsonDataAdapter;
import lesson6.json.adapters.UseDataAdapter;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
/**
* JsonSerializer converts Java objects to JSON representation.
*
*/
public class JsonSerializer {
/**
* simpleTypes contains java classes for which we should not make any deeper serialization and we should return object as is
* and use toString() method to get it serialized representation
*/
private static Set<Class> simpleTypes = new HashSet<Class>(Arrays.asList(
JSONObject.class,
JSONArray.class,
String.class,
Integer.class,
Short.class,
Long.class,
Byte.class,
Double.class,
Float.class,
Character.class,
Boolean.class,
int.class,
short.class,
long.class,
byte.class,
double.class,
float.class,
char.class,
boolean.class
));
/**
* Main method to convert Java object to JSON. If type of the object is part of the simpleTypes object itself will be returned.
* If object is null String value "null" will be returned.
* @param o object to serialize.
* @return JSON representation of the object.
*/
public static Object serialize(Object o) {
if (null == o) {
return "null";
}
if (simpleTypes.contains(o.getClass())) {
return o;
} else {
try {
return toJsonObject(o);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
/**
* Converts Java object to JSON. Uses reflection to access object fields.
* Uses JsonDataAdapter to serialize complex values. Ignores @Ignore annotated fields.
* @param o object to serialize to JSON
* @return JSON object.
* @throws IllegalAccessException
* @throws InstantiationException
*/
private static JSONObject toJsonObject(Object o) throws IllegalAccessException, InstantiationException, JSONException, NoSuchMethodException {
JSONObject m = new JSONObject();
JsonDataAdapter jda;
Class<?> c = o.getClass();
Field[] fields = c.getDeclaredFields();
for (Field f : fields){
if (f.isAnnotationPresent(Ignore.class)) continue;
f.setAccessible(true);
if(!f.isAnnotationPresent(UseDataAdapter.class))
m.put(f.getName(), JsonSerializer.serialize(f.get(o)));
else{
jda = f.getAnnotation(UseDataAdapter.class).value().newInstance();
m.put(f.getName(), jda.toJson(f.get(o)));
}
}
return m;
}
}