Gson不映射Java中的值

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

class User {
    @Expose
    private String name;

    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

public class GsonExample {
    public static void main(String[] args) {
        User user = new User("Alice", 25);

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

        String json = gson.toJson(user);
        System.out.println(json);  // 输出: {"name":"Alice"}
    }
}