POJO for this complex JSON

Question

I'm new to POJOs and am working on creating objects to represent JSON from Google APIs. How can I create a pojo for this JSON?

"notificationSettings": {
    "notifications": [
     {
      "type": "eventCreation",
      "method": "email"
     },
     {
      "type": "eventChange",
      "method": "email"
     },
     {
      "type": "eventCancellation",
      "method": "email"
     },
     {
      "type": "eventResponse",
      "method": "email"
     }
    ]
   }

I have the rest of the JSON figured out, however, the Gson.fromJSON() keeps returning null.

EDIT 1

This is what I have

private static class NotificationSettings{

        public NotificationSettings(){

        }

        public NotificationSettings(Map<String, List<Notification>> notifications) {
            super();
            this.setNotifications(notifications);
        }

        public Map<String, List<Notification>> getNotifications() {
            return notifications;
        }

        public void setNotifications(Map<String, List<Notification>> notifications) {
            this.notifications = notifications;
        }

        private Map<String, List<Notification>> notifications;


    }

    private static class Notification{

        public Notification(){

        }

        public Notification(String type, String method) {
            super();
            this.type = type;
            this.method = method;
        }

        private String type;
        private String method;
        /**
         * @return the type
         */
        public String getType() {
            return type;
        }
        /**
         * @param type the type to set
         */
        public void setType(String type) {
            this.type = type;
        }
        /**
         * @return the method
         */
        public String getMethod() {
            return method;
        }
        /**
         * @param method the method to set
         */
        public void setMethod(String method) {
            this.method = method;
        }


    }

EDIT 2 Another question, are the constructors with arguments required? In addition, is the toString() method required as well?

Thanks!

Answer 1

A POJO is a Plain Old Java Object, which is a class with fields and getters/setters. I don't think somebody that works with Java is new to POJOs unless it is learning Java. This is why I won't give the exact class structure, otherwise I would be doing your job.

You just need to define the type for the elements in your JSON string. Let's review the string and how can you map it:

"notificationSettings": { //name of class: NotificationSettings
    "notifications": [ //array of Notification objects. It means you will need a Notification class as well
                       //and an array or List field called notification in NotificationSettings class
     { //this defines the structure for Notification class
      "type": "eventCreation", //String field called type
      "method": "email" //String field called method
     },
     {
      "type": "eventChange",
      "method": "email"
     },
     {
      "type": "eventCancellation",
      "method": "email"
     },
     {
      "type": "eventResponse",
      "method": "email"
     }
    ]
}

From your implementation, looks like you should replace private Map<String, List<Notification>> notifications; field to private List<Notification> notifications; and make Notification class a top class in its own file.