Deserialize a JSON in Different ways

October 8, 2023

JSON(JavaScript Object Notation):

A text-based standard for encoding structured data based on JavaScript object syntax.
It is frequently used in online applications to transport data (such as passing data from the server to the client so it may be displayed on a web page, or vice versa).
It contains data in form of Key-Value pair.

example of a JSON object:

{
  "firstName": "SFDC",
  "lastName": "Elements"
}

example of JSON array:

[
  {
    "firstName": "SFDC",
    "lastName": "Elements"
  },
  {
    "firstName": "Welcome",
    "lastName": "To"
  },
  {
    "firstName": "My",
    "lastName": "Blog"
  }
]

1- Deserialize a JSON with & without Wrapper Class:

{
  "firstName": "SFDC",
  "lastName": "Elements"
}

public class JSONExampleClass {
    //With wrapper class
    public static void deseriliazeJsonWithWrapper(){
        String jsonObj='{"firstName":"SFDC", "lastName":"Elements"}';
        JSONWrapper empData=(JSONWrapper)JSON.deserialize(jsonObj, JSONWrapper.class);
        /*If you wont type cast with your wrapper class then it will throw error of
        Illegal assignment from Object to JSONExampleClass.JSONWrapper*/
        System.debug('check firstName::'+empData.firstName);
        System.debug('check lastName::'+empData.lastName);
    }
    
    public class JSONWrapper{
        public String firstName;
        public String lastName;
    }
    
    //Without Wrapper class
    public static void deseriliazeJsonWithoutWrapper(){
        String jsonObj='{"firstName":"SFDC", "lastName":"Elements"}';
        //if there is a JSON object then untyped return as Map<String,Object>
        Map<String,Object> empMap=(Map<String,Object>)JSON.deserializeUntyped(jsonObj);
        /*If you wont type cast with your wrapper class then it will throw error of
        Illegal assignment from Object to Map<String,Object>*/
        for(String key:empMap.keySet()){
            String jsonKey=key;
            String JsonValue=String.valueOf(empMap.get(key));
            System.debug(jsonKey+'::'+JsonValue);
        }
        
        System.debug('value when you know the key::'+String.valueOf(empMap.get('firstName'))+' '+String.valueOf(empMap.get('lastName')));
    }
}

Output:

2- Deserialize a JSON Array with & without Wrapper Class:

[
  {
    "firstName": "SFDC",
    "lastName": "Elements"
  },
  {
    "firstName": "Welcome",
    "lastName": "To"
  },
  {
    "firstName": "My",
    "lastName": "Blog"
  }
]

public class JSONArrayExampleClass {
    public static void deseriliazeJsonArrayWithWrapper(){
        String jsonData='[{"firstName":"SFDC","lastName":"Elements"},{"firstName":"Welcome","lastName":"To"},{"firstName":"My","lastName":"Blog"}]';
        //With wrapper class
        List<JSONWrapper> empData=(List<JSONWrapper>)JSON.deserialize(jsonData, List<JSONWrapper>.class);
        /*If you wont type cast with your list<wrapper class> then it will throw error of
        Illegal assignment from Object to List<JSONArrayExampleClass.JSONWrapper>*/
        for(JSONWrapper jwrap:empData){
            System.debug('check firstName::'+jwrap.firstName);
        	System.debug('check lastName::'+jwrap.lastName);
        }
    }
    
    public class JSONWrapper{
        public String firstName;
        public String lastName;
    }
    
    //without wrapper class
    public static void deseriliazeJsonArrayWithoutWrapper(){
        String jsonData='[{"firstName":"SFDC","lastName":"Elements"},{"firstName":"Welcome","lastName":"To"},{"firstName":"My","lastName":"Blog"}]';
        //if there is a JSON Array then untyped return as List<Object>
        List<Object> empData=(List<Object>)JSON.deserializeUntyped(jsonData);
        /*If you wont type cast with your list<wrapper class> then it will throw error of
        Illegal assignment from Object to List<Object>*/
        for(Object empObj:empData){
            //now each empObj is a JSON object so we need to convert it in Map<String,Object>
            Map<String,Object> empMap=(Map<String,Object>)empObj;
            for(String key:empMap.keySet()){
                String jsonKey=key;
                String JsonValue=String.valueOf(empMap.get(key));
                System.debug(jsonKey+'::'+JsonValue);
            }
            System.debug('value when you know the key::'+String.valueOf(empMap.get('firstName'))+' '+String.valueOf(empMap.get('lastName')));
        }
    }
}

3- Deserialize a Nested JSON with & without Wrapper Class:

{
  "firstName": "John",
  "lastName": "Smith",
  "gender": "male",
  "age": 32,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "fax",
      "number": "646 555-4567"
    }
  ]
}

public class NestedJSONExample {
    public static void deserilizeNestedJSONwithWrapper(){
        String jsonString='{"firstName":"John","lastName":"Smith","gender":"male","age":32,"address":{"streetAddress":"21 2nd Street","city":"New York","state":"NY","postalCode":"10021"},"phoneNumbers":[{"phoneType":"home","phoneNumber":"212 555-1234"},{"phoneType":"fax","phoneNumber":"646 555-4567"}]}';
        
        MainWrapper mainWrap=(MainWrapper) JSON.deserialize(jsonString,MainWrapper.class);
        
        System.debug('check firstName::'+mainWrap.firstName);
        //similarily for lastName,gender and age
        
        System.debug('check street from address::'+mainWrap.address.streetAddress);
        //similarily for city,state and postalCode mainWrap.address.city,mainWrap.address.state,mainWrap.address.postalCode
        
        //loop to get all the phoneNumbers as this is an array
        for(PhoneWrapper phoneWrap: mainWrap.phoneNumbers){
            System.debug('check phoneType::'+phoneWrap.phoneType);
            System.debug('check phoneNumber::'+phoneWrap.phoneNumber);
        }
    }
    
    public class MainWrapper{
        public String firstName;
        public String lastName;
        public String gender;
        public Integer age;
        public AddressWrapper address; //as address is a JSON object here so taking as object of AddressWrapper
        public List<PhoneWrapper> phoneNumbers; //as phoneNumbers is JSON Array so taking as List<PhoneWrapper>
    }
    
    public class AddressWrapper{
        public String streetAddress;
        public String city;
        public String state;
        public String postalCode;
    }
    
    public class PhoneWrapper{
        public String phoneType;
        public String phoneNumber;
    }
    
    
    public static void deserilizeNestedJSONwithoutWrapper(){
        String jsonString='{"firstName":"John","lastName":"Smith","gender":"male","age":32,"address":{"streetAddress":"21 2nd Street","city":"New York","state":"NY","postalCode":"10021"},"phoneNumbers":[{"phoneType":"home","phoneNumber":"212 555-1234"},{"phoneType":"fax","phoneNumber":"646 555-4567"}]}';
        
        Map<String,Object> jsonMap=(Map<String,Object>) JSON.deserializeUntyped(jsonString);
        
        System.debug('check lastName::'+jsonMap.get('lastName'));
        //similarily for firstName,gender and age
        
        Map<String,Object> addressMap=(Map<String,Object>)jsonMap.get('address');
        String city=String.valueOf(addressMap.get('city'));
        System.debug('check city::'+city);
        //similarily for streetAddress,state and postalCode
        
        //loop to get all the phoneNumbers as this is an array
        List<Object> phoneList=(List<Object>)jsonMap.get('phoneNumbers');
        for(Object phoneObj: phoneList){
            Map<String,Object> phoneMap=(Map<String,Object>)phoneObj;
            String phoneType=String.valueOf(phoneMap.get('phoneType'));
            String phoneNumber=String.valueOf(phoneMap.get('phoneNumber'));
            System.debug('check phoneType::'+phoneType);
        	System.debug('check phoneNumber::'+phoneNumber);
        }
    }
}