如何在 Java Spring 上获取字段变量

Question

我的学习项目有问题，例如“如果条件值为空，然后如果条件值字段为空”，例如我的代码遵循这些代码：

对于实体 Users.java :

@Entity
public class Users {
    private Long id;
    private String employeeId;
    private String fullName;
    private String username;
    private String password;
    ...

    public Users() {
    }

    Some Code Setter and Getter....
}

对于实体 Employee.java :

@Entity
public Class Employee {
    private Long id;
    private String employeeId;
    private String fullName;
    ...
    
    public Employee() {
    }
    
    Some Code Setter and Getter....
}

然后对于我的 Class 服务，我有插入数据 Employee with Repository 的案例。如果我们在向 table Employee 插入数据之前有验证数据，我们需要检查 table users not null 然后在字段 employeeId 应该为空。我的代码如下：

对于存储库 UserRepo.java 和 EmployeeRepo.java :

@Repository
public interface EmployeeRepo extends CrudRepository<Employee, Long> {

}

@Repository
public interdace UsersRepo extends CrudRepository<Users, Long> {

@Transactional
@Modifying(clearAutomatically = true, flushAutomatically = true)
@Query("UPDATE Users u SET u.employeeId = :employeeId WHERE u.id = :id")
public void updateEmployeeIdUsers(@Param("id") Long id, @Param("employeeId") String employeeId);

}

服务 UsersService.java :

@Service("usersService")
public class UsersService {
    
    @Autowired
    private UsersRepo repo;
    
    public Optional<Users> findById(Long id) {
        return repo.findById(id);
    }
    
    public void updateEmployeeIdUsers(Long id, String employeeId) {
        repo.updateEmployeeIdUsers(id, employeeId);
    }

}

服务 EmployeeService.java :

@Service("employeeService")
public class EmployeeService {
    
    @Autowired
    private EmployeeRepo employeeRepo;
    
    @Autowired
    private UsersService userService;
    
    public Employee insertEmployee(Employee employee) throws Exception {
        Optional<Users> users = userService.findById(employee.getId());
        Users userOptional = new Users(); **//on this my problem**
        userOptional.getEmployeeId(); **//on this my problem**
        if (!users.isPresent()) {
            throw new Exception("User ID : "+ employee.getId() +" Not Founded");
        }else if (!(userOptional == null)) { **//on this my problem**
            throw new Exception("User employeID : "+ employee.getEmployeeId() +" Already Exist on Users");
        }
        
        String str1 = "TEST";
        Long idUser = employee.getId();
        userService.updateEmployeeIdUsers(idUser, str1);
        return employeeRepo.save(employee);
    }

}

在这段代码中，如果 userOptional 始终为 NULL，我们在 else 上遇到问题，我尝试调试以查看 employeeId 上的值，只是我总是看到 Null。所以对我的问题有任何想法，因为我尝试了一些案例总是因我的问题而失败。如果对我的问题有任何想法，请回答我的这些问题。非常感谢你回答我的问题。

Answer 1

看完评论我已经明白你的问题了。

Users users = userService.findById(employee.getId()).orElseThrow(() -> new Exception("User ID : "+ employee.getId() +" Not Founded"));

现在您可以从返回的 userService.findById(employee.getId());

中获取 users 中的 employeeId

示例：

String employeeId = users.getEmployeeId(); // reference to your code

但在这种情况下，我认为你应该在 users 和 employee 之间建立关系 @OneToOne 或在 employee [=34= 中扩展 users ].

One-To-One relation in JPA, hibernate-inheritance

Answer 2

对于建议的解决方案，我将假设如下：

Employee和Users有关系。
一个Employee只能关联一个Users
username是Users
employeeId是Employee

所以实体:

@Entity
public class Users {

  @Id
  // This one is an example, you can use the configuration you need
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator= "users_seq")
  @SequenceGenerator(name="users_seq", initialValue=1, allocationSize=1, sequenceName = "users_id_seq")
  private Long id;

  @Column(name = "fullname")
  private String fullName;

  // Probably this column should be unique and you need to configure in that way here and in your database
  @Column
  private String username;

  @Column
  private String password;

  // Getter & setter & constructors
}



@Entity
public class Employee {

  @Id
  // This one is an example, you can use the configuration you need
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator= "employee_seq")
  @SequenceGenerator(name="employee_seq", initialValue=1, allocationSize=1, sequenceName = "employee_id_seq")
  private Long id;

  /**
   * Assuming this is your specific identifier for an employee (not related with database PK)
   *    If the assumption is correct, this column should be unique and you need to configure in
   * that way here and in your database
   */
  @Column(name = "employeeid")
  private String employeeId;

  /**
   * Not sure if this relation could be nullable or not
   */
  @OneToOne
  @JoinColumn(name = "users_id")
  private Users users;

  // Getter & setter & constructors
}

如您所见，两个实体中都没有“重复列”，并且 Employee 和 [=] 之间存在 单向 OneToOne 关系14=]。如果你需要一个双向的，link 会帮助你：Bidirectional OneToOne

存储库:

@Repository
public interface UsersRepository extends CrudRepository<Users, Long> {
  Optional<Users> findByUsername(String username);
}



@Repository
public interface EmployeeRepository extends CrudRepository<Employee, Long> {
  Optional<Employee> findByEmployeeId(String employeeId);
}

服务：

@Service
public class UsersService {

  @Autowired
  private UsersRepository repository;

  public Optional<Users> findByUsername(String username) {
    return Optional.ofNullable(username)
            .flatMap(repository::findByUsername);
  }

  public Optional<Users> save(Users user) {
    return Optional.ofNullable(user)
            .map(repository::save);
  }
}



@Service
public class EmployeeService {

  @Autowired
  private EmployeeRepository repository;

  @Autowired
  private UsersService usersService;

  public Optional<Employee> insert(Employee newEmployee) {
    /**
     * The next line don't make sense:
     *
     *   Optional<Users> users = userService.findById(employee.getId());
     *
     * I mean:
     *
     *  1. Usually, id column is configured with @GeneratedValue and manage by database. So you don't need to ask
     *     if that value exists or not in Users.
     *
     *  2. Even if you are including id's values manually in both entities what should be "asked" is:
     *
     *    2.1 Is there any Users in database with the same username than newEmployee.users.username
     *    2.2 Is there any Employee in database with the same employeeId
     *
     *    Both ones, are the natural keys of your entities (and tables in database).
     */
    return Optional.ofNullable(newEmployee)
            .filter(newEmp -> null != newEmp.getUsers())
            .map(newEmp -> {
                isNewEmployeeValid(newEmp);

                // Required because newEmp.getUsers() is a new entity (taking into account the OneToOne relation)
                usersService.save(newEmp.getUsers());

                repository.save(newEmp);
                return newEmp;
            });
  }

  private void isNewEmployeeValid(Employee newEmployee) {
    if (usersService.findByUsername(newEmployee.getUsers().getUsername()).isPresent()) {
        throw new RuntimeException("Username: "+ newEmployee.getUsers().getUsername() +" exists in database");
    }
    if (repository.findByEmployeeId(newEmployee.getEmployeeId()).isPresent()) {
        throw new RuntimeException("EmployeeId: "+ newEmployee.getEmployeeId() +" exists in database");
    }
  }
}

如何在 Java Spring 上获取字段变量

How to get Field Variable on Java Spring

java

spring

entity

field

spring-boot