GSON - Versioning Support

Gson provides @Since annotation to control the Json serialization/deserialization of a class based on its various versions. Consider the following class with versioning support. In this class, we've initially defined two variables rollNo and name and later on, we added verified as a new variable. Using @Since, we've defined rollNo and name as of version 1.0 and verified to be of version 1.1.

class Student { 
   @Since(1.0) 
   private int rollNo; 
   
   @Since(1.0) 
   private String name; 
   
   @Since(1.1) 
   private boolean verified;  
}

GsonBuilder provides the setVersion() method to serialize such versioned class.

GsonBuilder builder = new GsonBuilder(); 
builder.setVersion(1.0);   
Gson gson = builder.create();

Example - Versioning Support

Let's see an example of versioning support in action.

GsonTester.java

package com.tutorialspoint;

import com.google.gson.Gson; 
import com.google.gson.GsonBuilder; 
import com.google.gson.annotations.Since;  

public class GsonTester { 
   public static void main(String args[]) { 
   
      GsonBuilder builder = new GsonBuilder(); 
      builder.setVersion(1.0);   
      Gson gson = builder.create();
      
      Student student = new Student(); 
      student.setRollNo(1); 
      student.setName("Mahesh Kumar"); 
      student.setVerified(true);  
      
      String jsonString = gson.toJson(student); 
      System.out.println(jsonString);  
      
      gson = new Gson();     
      jsonString = gson.toJson(student); 
      System.out.println(jsonString); 
   }      
} 

class Student { 
   @Since(1.0) 
   private int rollNo; 
   
   @Since(1.0) 
   private String name; 
   
   @Since(1.1) 
   private boolean verified;   
   
   public int getRollNo() { 
      return rollNo; 
   }  
   
   public void setRollNo(int rollNo) { 
      this.rollNo = rollNo; 
   } 
   
   public String getName() { 
      return name; 
   } 
   
   public void setName(String name) { 
      this.name = name; 
   }
   
   public void setVerified(boolean verified) { 
      this.verified = verified; 
   }  
   
   public boolean isVerified() { 
      return verified; 
   } 
} 

Output

Run the GsonTester and verify the output.

{"rollNo":1,"name":"Mahesh Kumar"} 
{"rollNo":1,"name":"Mahesh Kumar","verified":true}