com.google.firebase.database.DatabaseException:无法将java.lang.String类型的对象转换为com.example.prj.User类型

public class User {
    private String name;
    private int age;

    // 默认构造函数
    public User() {}

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

    // Getter 和 Setter 方法
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}

{
    "name": "John Doe",
    "age": 30
}

public class User {
    private String name;
    private int age;

    // 默认构造函数
    public User() {}

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

    // Getter 和 Setter 方法
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}

DatabaseReference ref = FirebaseDatabase.getInstance().getReference("users").child(userId);
ref.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        try {
            User user = dataSnapshot.getValue(User.class);
            if (user != null) {
                // 处理用户数据
            } else {
                Log.e("FirebaseData", "User data is null");
            }
        } catch (Exception e) {
            Log.e("FirebaseData", "Error converting data", e);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.e("FirebaseData", "Database error", databaseError.toException());
    }
});