Java 尝试从实体获取自动生成的id时获取null，该实体是通过使用JPARepository的findByVariable方法获取的

我有这个模型：

User.java

@Entity
@Table(name = "`user`")
public class User {
    private Long id;
    private String username;
    private String phone;

    @Override
    public int hashCode() {
        return new Long(id).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (!(obj instanceof User)) {
            return false;
        }
        return this.id == ((User) obj).getId();
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Long getId() {
        return id;
    }

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

    (...other getters and setters...)

}

(...)

@RequestMapping(value = "/user/updatePhone", method = RequestMethod.GET)
public String updatePhone(Model model) {
    model.addAttribute("userForm", userService.findByUsername("testUsername"));
    return "user/updatePhone";
}

@RequestMapping(value = "/user/updatePhone", method = RequestMethod.POST)
public String updatePhone(@ModelAttribute("userForm") User userForm, BindingResult bindingResult, Model model) {
    userService.updatePhone(userForm);
    return "redirect:/user/view";
}

(...)

@Service
@Transactional
public class UserServiceImpl implements UserService {

    (...)

    @Override
    public void updatePhone(User user) {
        User entity = userRepository.findById(user.getId());
        if (entity != null) {
            entity.setPhone(user.getPhone());
        }
    }

    (...)

}

我的控制器中的这段代码：

UserController.java

@Entity
@Table(name = "`user`")
public class User {
    private Long id;
    private String username;
    private String phone;

    @Override
    public int hashCode() {
        return new Long(id).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (!(obj instanceof User)) {
            return false;
        }
        return this.id == ((User) obj).getId();
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Long getId() {
        return id;
    }

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

    (...other getters and setters...)

}

(...)

@RequestMapping(value = "/user/updatePhone", method = RequestMethod.GET)
public String updatePhone(Model model) {
    model.addAttribute("userForm", userService.findByUsername("testUsername"));
    return "user/updatePhone";
}

@RequestMapping(value = "/user/updatePhone", method = RequestMethod.POST)
public String updatePhone(@ModelAttribute("userForm") User userForm, BindingResult bindingResult, Model model) {
    userService.updatePhone(userForm);
    return "redirect:/user/view";
}

(...)

@Service
@Transactional
public class UserServiceImpl implements UserService {

    (...)

    @Override
    public void updatePhone(User user) {
        User entity = userRepository.findById(user.getId());
        if (entity != null) {
            entity.setPhone(user.getPhone());
        }
    }

    (...)

}

在我的服务中：

UserServiceImpl.java

@Entity
@Table(name = "`user`")
public class User {
    private Long id;
    private String username;
    private String phone;

    @Override
    public int hashCode() {
        return new Long(id).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (!(obj instanceof User)) {
            return false;
        }
        return this.id == ((User) obj).getId();
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Long getId() {
        return id;
    }

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

    (...other getters and setters...)

}

(...)

@RequestMapping(value = "/user/updatePhone", method = RequestMethod.GET)
public String updatePhone(Model model) {
    model.addAttribute("userForm", userService.findByUsername("testUsername"));
    return "user/updatePhone";
}

@RequestMapping(value = "/user/updatePhone", method = RequestMethod.POST)
public String updatePhone(@ModelAttribute("userForm") User userForm, BindingResult bindingResult, Model model) {
    userService.updatePhone(userForm);
    return "redirect:/user/view";
}

(...)

@Service
@Transactional
public class UserServiceImpl implements UserService {

    (...)

    @Override
    public void updatePhone(User user) {
        User entity = userRepository.findById(user.getId());
        if (entity != null) {
            entity.setPhone(user.getPhone());
        }
    }

    (...)

}

---

我的问题是，当我试图从UserServiceImpl类中的用户对象获取id时，得到的是null。你知道我必须做什么才能在我的用户对象中正确设置id吗？可能是userRepository类的findByUsername（…）方法有问题，该方法返回的对象没有id（这是我的模型中@id和@GeneratedValue（…）注释的前奏）。

表单中有id吗？@JalalSordo:我不完全理解你的问题。你是说它使用的语言吗？通常，在我的应用程序中，我以类似的方式使用JPA存储库来创建/更新/删除数据库中的记录，一切正常。我对这个具体的例子有问题。@ChiefTwoPencils:我在表单中没有使用id-我在表单中只有一个用于更改phone变量的输入。我确信包括id在内的完整用户会在返回时与用户一起返回，对吗？这篇文章的内容是什么？我对sqlserver2008也有类似的问题，请尝试GenerationType.IDENTITY。