How to implement custom JSON de-serialization with Gson in Java?n

A Gson library provides a way to specify custom de-serializers by registering a custom de-serializer with the GsonBuilder if we need a way to convert a java object to JSON. We can create a custom de-serializer by overriding the deserialize() method of com.google.gson.JsonDeserializer class.

In the below example, the implementation of custom de-serialization of JSON.

Example

import java.lang.reflect.Type;
import com.google.gson.*;
public class CustomJSONDeSerializerTest {
   public static void main(String[] args) {
      Gson gson = new GsonBuilder().registerTypeAdapter(Password.class, new          PasswordDeserializer()).setPrettyPrinting().create();
      String jsonStr = "{" +
                          "\"firstName\": \"Adithya\"," +
                          "\"lastName\": \"Sai\"," +
                          "\"age\": 25," +
                          "\"address\": \"Pune\"," +
                          "\"password\": \"admin@123\"" +
                       "}";
      Student student = gson.fromJson(jsonStr, Student.class);
      System.out.println(student.getPassword().getPassword());
   }
}
class PasswordDeserializer implements JsonDeserializer {
   @Override
   public Password deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)      throws JsonParseException {
      String ecryptedPwd = json.getAsString();
      return new Password(new StringBuffer(ecryptedPwd).toString());
   }
}
// Student class
class Student {
   private String firstName;
   private String lastName;
   private int age;
   private String address;
   private Password password;
   public Student(String firstName, String lastName, int age, String address) {
      super();
      this.firstName = firstName;
      this.lastName = lastName;
      this.age = age;
      this.address = address;
   }
   public String getFirstName() {
      return firstName;
   }
   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }
   public String getLastName() {
      return lastName;
   }
   public void setLastName(String lastName) {
     this.lastName = lastName;
   }
   public int getAge() {
      return age;
   }
   public void setAge(int age) {
      this.age = age;
   }
   public String getAddress() {
      return address;
   }
   public void setAddress(String address) {
      this.address = address;
   }
   public Password getPassword() {
      return password;
   }
   public void setPassword(Password password) {
      this.password = password;
   }
   public String toString() {
      return "Student[ " +
                "firstName = " + firstName +
                ", lastName = " + lastName +
                ", age = " + age +
                ", address = " + address +
            " ]";
   }
}
// Password class
class Password {
   private String password;
   public Password(String password) {
      super();
      this.password = password;
   }
   public String getPassword() {
      return password;
   }
   public void setPassword(String password) {
      this.password = password;
   }
}

Output

admin@123