Gson custom field name with @SerializedName

When the JSON field name doesn’t exactly match the Java object field names, we can use @SerializedName to change the JSON’s matching field name in Gson.

Table of contents:

• 1. Setup Google Gson
• 2. JSON Unrecognized Field
• 3. Custom field name with @SerializedName
• 4. Download Source Code
• 5. References

P.S Tested with Gson 2.10.1

1. Setup Google Gson

Declare gson in the pom.xml.

    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.10.1</version>
    </dependency>

2. JSON Unrecognized Field

Review the JSON data below. The JSON field name nick_name doesn’t match the Person name. If we use Gson to do the data binding, the Person name will be null.

{
  "nick_name": "mkyong",
  "age": 42
}

public class Person {

    private String name;
    private int age;

    //getters, setters, constructors and etc...
}

package com.mkyong.json.gson;

import com.google.gson.Gson;
import com.mkyong.json.model.Person;

public class GsonCustomFieldNameExample {

    public static void main(String[] args) {

        String json = "{\"nick_name\":\"mkyong\",\"age\":42}";

        Gson gson = new Gson();

        // nick_name => name?
        Person person = gson.fromJson(json, Person.class);

        System.out.println(person);
    }

}

Output

    Person{name='null', age=42}

3. Custom field name with @SerializedName

In Gson, we can use @SerializedName to change the JSON’s matching field name.

package com.mkyong.json.model;

import com.google.gson.annotations.SerializedName;

public class Person {

    // custom field name
    // match `nick_name` to `name`
    @SerializedName("nick_name")
    private String name;
    
    private int age;

    //getters, setters, constructors and etc...
}

Below is the JSON serialization and deserialization example using Gson to match JSON field name nick_name to the Person field name name.

package com.mkyong.json.gson;

import com.google.gson.Gson;
import com.mkyong.json.model.Person;

public class GsonCustomFieldNameExample {

    public static void main(String[] args) {

        String json = "{\"nick_name\":\"mkyong\",\"age\":42}";

        Gson gson = new Gson();

        // Deserialize JSON to Java object
        Person person = gson.fromJson(json, Person.class);

        // Serialize Java object back to JSON
        System.out.println(person);

        String newJson = gson.toJson(person);

        System.out.println("Serialized JSON: " + newJson);

    }

}

Output

    Person{name='mkyong', age=42}
    Serialized JSON: {"nick_name":"mkyong","age":42}

4. Download Source Code

5. References

• Google Gson Github
• How to convert Java object to / from JSON using Gson
• How to parse JSON using Gson
• Jackson Custom field name with @JsonProperty

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