Json Gson：@Expose 与 @SerializedName

Even if it's late I wanted to answer this question. To explain it we must know what is serialization and deserialization. serialization is converting object into json string and deserialization is converting json string into object.

Let's say we've User class with no annotations.

public class User{
    private String userName;
    private Integer userAge;

    public User(String name, Integer age){
        userName = name;
        userAge = age;
    }
}

And we serialize this object as below

User user = new User("Ahmed", 30);
Gson gson = new Gson();
String jsonString = gson.toJson(user);

Json字符串如下

{
    "userName":"Ahmed",
    "userAge":30
}

If we add annotation @SerializedName

public class User{

    @SerializedName("name")
    private String userName;
    @SerializedName("age")
    private Integer userAge;

    public User(String name, Integer age){
        userName = name;
        userAge = age;
    }
}

Json字符串如下

{
    "name":"Ahmed",
    "age":30
}

@Expose is used to allow or disallow serialization and deserialization. @Expose is optional and it has two configuration parameters: serialize and deserialize. By default they're set to true. To serialize and deserialize with @Expose we create gson object like this

Gson gsonBuilder = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();

低于userName的不会被反序列化.用户名的值将为null.

@SerializedName("name")
@Expose(deserialize = false)
private String userName;

低于userName将不会被序列化.

@SerializedName("name")
@Expose(serialize = false)
private String userName;

Json字符串如下. Only userAge will be deserialized.

{
    "age":30
}