无法解析“optional”中的方法“get name”

Question

我希望使用gettergetName()获取数据库的值。首先,我创建了user.java：

package ch.concertopro.webshopanalyser.entity;

import javax.persistence.*;

@Entity(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String name;
    @Column(unique = true, nullable = false)
    private String email;
    private String dob;


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getDob() {
        return dob;
    }

    public void setDob(String dob) {
        this.dob = dob;
    }
}

那么我已经创建了userRepository.java：

package ch.concertopro.webshopanalyser.repository;

import ch.concertopro.webshopanalyser.entity.User;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends CrudRepository<User, Integer> {

}

这是我尝试获取getName()值的服务：

package ch.concertopro.webshopanalyser.service;

import ch.concertopro.webshopanalyser.entity.User;
import ch.concertopro.webshopanalyser.repository.UserRepository;
import org.springframework.stereotype.Service;

@Service
public class UserService {
final UserRepository userRepository;

    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public Iterable<User> getUser() {
        return userRepository.findById(1).getName();
    }
}

但我得到的错误是无法解析“optional”中的方法“get name”。为什么？

Answer 1

为了达到您的目的，您应该更改您的方法实现，如下所示：

java prettyprint-override">public Optional<String> getUser() {
    return userRepository.findById(1)
                         .map(User::getName);
}