Gson serialize exclude key from Hashmap - json

Question

My class is this
public class GiftCard {
Map<String, Object> extendedProperties;
String expiryDate;
double originalAmount;
String cardNumber;
}
The hashmap has many values including <"pin" : 1234 >
When I do log(gson.json(giftCard)), it prints the pin too.
How can I prevent the pin from getting logged (while logging other values in extendedProperties)?

Answer 1

You don't want to change the original pin value, you'll need it right? Then you should use toString method. Modify your GiftCard class. see code below and the comments in it. Actually there are more comments than code there:
public class GiftCard implements Cloneable {
Map<String, Object> extendedProperties;
String expiryDate;
double originalAmount;
String cardNumber;
#Override
protected Object clone() throws CloneNotSupportedException {
GiftCard cloned = (GiftCard)super.clone();
// the default behavior of clone() is to return a shallow copy of the object.
// This means that the values of all of the original object’s fields are copied to the fields of the new object.
// If the fields are primitive types, the changes made to this object will not be reflected to cloned ones.
// But if the fields are not primitive, only their references are cloned,
// which means any change on that fields, are applied to original and the cloned objects.
// So here we have to get a copy of your hash map.
cloned.extendedProperties = new HashMap<String, Object>(this.extendedProperties);
return cloned;
}
#Override
public String toString() {
try {
GiftCard giftCardToPrint = null;
GsonBuilder gsonBuilder = new GsonBuilder();
Gson gson = gsonBuilder.create();
if(this.extendedProperties != null && this.extendedProperties.get("pin") != null) {
// You don't want to change the original pin value so clone original instance, see clone method.
giftCardToPrint = (GiftCard) this.clone();
giftCardToPrint.extendedProperties.put("pin", "*");
} else {
giftCardToPrint = this;
}
return gson.toJson(giftCardToPrint);
} catch (Exception e) {
e.printStackTrace();
return super.toString();
}
}
}
Try below code:
System.out.println("giftCard toString:" + giftCard.toString());
System.out.println("giftCard toJson :" + gson.toJson(giftCard));
System.out.println("giftCard.pin :" + giftCard.extendedProperties.get("pin"));
Output:
giftCard toString:{"cardNumber":"1111 2222 3333 4444","extendedProperties":{"pin":"*"},"originalAmount":0.0}
giftCard toJson :{"cardNumber":"1111 2222 3333 4444","extendedProperties":{"pin":"1234"},"originalAmount":0.0}
giftCard.pin :1234