Google%20Gson%20Interview%20Questions%20and%20Answers

Question: What is Versioning Support in Gson?

Answer:

This is excellent feature you can use, if the class file you are working has been modified in different versions and fields has been annotated with @Since. All you need to do is to use setVersion() method of GsonBuilder.

GsonBuilder gsonBuilder = new GsonBuilder();

gsonBuilder.registerTypeAdapter(Date.class, new DateSerializer());

gsonBuilder.registerTypeAdapter(Date.class, new DateDeserializer());

//Specify the version like this

gsonBuilder.setVersion(1.0);

Gson gson = gsonBuilder.create();

Fields added in various versions in Employee.java

public class Employee

{

@Since(1.0)

private Integer id;

private String firstName;

private String lastName;

@Since(1.1)

private List<String> roles;

@Since(1.2)

private Date birthDate;

//Setters and Getters

}

Now test the version feature:

//Using version 1.0 fields

gsonBuilder.setVersion(1.0);

Output:

{

"id":1,

"firstName":"Bob",

"lastName":"Richardson"

}

//Using version 1.1 fields

gsonBuilder.setVersion(1.1);

Output:

{

"id":1,

"firstName":"Bob",

"lastName":"Richardson",

"roles":["FINANCE","MANAGER"]

}

//Using version 1.2 fields

gsonBuilder.setVersion(1.2);

Output:

{

"id":1,

"firstName":"Bob",

"lastName":"Richardson",

"roles":["FINANCE","MANAGER"],

"birthDate":"17/06/2014"

}

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