What is the basic purpose of @SerializedName annotation in Android using Gson

Question

Java class example,

public class Person {

    @SerializedName("name")
    private String personName;

    @SerializedName("bd")
    private String birthDate;

}

This class has two fields that represent the person name and birth date of a person. These fields are annotated with the @SerializedName annotation. The parameter (value) of this annotation is the name to be used when serialising and deserialising objects. For example, the Java field personName is represented as name in JSON.

JSON Example,

{
    "name":"chintan",
    "bd":"01-01-1990"
}

There are already few answers here,but I would like to add that if you are using ProGuard to Obfuscate your code & don't use @SerializedName("name") in your model class, then your GSON won't work. Because due to obfuscation, your variable names might have changed from String name to String a resulting into broken GSON parsing as GSON will look for key a into json & it will fail.

By specifying @SerializedName, GSON will not look in json based on variable name & will just use specified @SerializedName.

Of Course you can tell proguard to not obfuscate your model, but if you would like to have model obfuscated, then you must specify @SerializedName

Using @SerializedName you are actually telling the Parser when receiving a callback from the server i.e. of a Json format:

{
    "name":"John Doe",
}

that when Serializing or Deserializing an object to instead of searching for a key named: "userName", in the Json response, to search for "name".

@SerializedName("name")
var userName: String,

This is good because you may have a model that you would like it to have its members being called with whatever you like.

You can instruct Proguard to not obfuscate your data classes by specifying @Keep on top of the class. This will neither remove nor obfuscate your class. No need to add @SerializedName to each and every field explicitly if the field name is similar to the Json key being used for it.