如何使用 JPA 存储库更新实体中的一个字段

Question

我的实体有 3 个字段：id、姓氏和电话号码。我想创建适用于更新所有字段或仅更新一两个字段的方法。

我使用 Hibernate 和 JPA 存储库。当我尝试更新所有字段时，一切正常，但例如，当我只想更新姓氏而不更改电话号码时，我在输出中插入了旧电话号码的 null 。

这是我在控制器中的方法：

@PutMapping("/students/update/{id}")
public String updateStudentById(@ModelAttribute Student student, @ModelAttribute StudentDetails studentDetails,
                                String lastname, String phoneNumber,
                                @PathVariable Long id) {

    Optional<Student> resultOptional = studentRepository.findById(id); 

    //Student result =resultOptional.get();
    resultOptional.ifPresent((Student result) -> {
           result.getStudentDetails().setPhoneNumber(studentDetails.getPhoneNumber());     result.getStudentDetails().setLastname(studentDetails.getLastname());
        studentRepository.save(result);
    });
    return "Student updated";
}

更新的类：

@DynamicUpdate
@Entity
public class StudentDetails {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name="lastname")
    private String lastname;
    @Column(name="phone_number")
    private String phoneNumber;

    public StudentDetails() {
    }

    public StudentDetails(Long id, String lastname, String phoneNumber) {
        this.id = id;
        this.lastname = lastname;
        this.phoneNumber = phoneNumber;
    }

    public Long getId() {
        return id;
    }

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

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }
}

与StudentDetails相关的类：

@Entity
@Table(name = "student")
@DynamicUpdate
public class Student {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name")
    private String name;
    @Column(name = "email")
    private String email;

    //@OneToMany(mappedBy = "student")
    @ManyToMany
    @JoinTable(name="course_student",joinColumns = @JoinColumn(name="student_id"),
    inverseJoinColumns = @JoinColumn(name="course_id"))

    private List<Courses> courses;

    @OneToOne(cascade = CascadeType.ALL)
   // @JoinColumn(name="studen/_details_id") // with this we have dobule student_details column
    private  StudentDetails studentDetails;


    public List<Courses> getCourses() {
        return courses;
    }

    public void setCourses(List<Courses> courses) {
        this.courses = courses;
    }

    public StudentDetails getStudentDetails() {
        return studentDetails;
    }

    public void setStudentDetails(StudentDetails studentDetails) {
        this.studentDetails = studentDetails;
    }

    // Methods for StudentViewController
    public String getLastname(){
        return studentDetails.getLastname();
    }
    public String getPhoneNumber(){
        return studentDetails.getPhoneNumber();
    }

    public Student() {
    }

    public Student(String name, String email, StudentDetails studentDetails) {
       // this.id = id;
        this.name = name;
        this.email = email;
        this.studentDetails = studentDetails;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long 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;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", email='" + email + '\'' +
                '}';
    }

}

我正在寻找解决方案并添加了@DynamicUpdate，但它仍然不起作用。

Answer 1

你的代码工作正常。lastName当您仅在请求中提供参数时，该phoneNumber参数将被映射到null，以便您使用该值覆盖phoneNumer实体中的属性null。

按以下方式更改代码：

resultOptional.ifPresent((Student result) -> {
   if(studentDetails.getPhoneNumber()!=null) {
     result.getStudentDetails().setPhoneNumber(studentDetails.getPhoneNumber());     
   }
   if(studentDetails.getLastname()!=null) {
     result.getStudentDetails().setLastname(studentDetails.getLastname());
   }
   studentRepository.save(result);
});

不幸的是，它引发了另一个问题：如何删除这些字段？（如何将它们明确设置为null？）

如果您检查""（空字符串）并将属性设置为“null如果参数为空字符串”，则可能是解决方案。

无论如何，这将是一个相当混乱的代码......

您应该考虑使用 Spring Data Rest 包。它会自动为您的实体创建所有标准 REST 端点，并立即处理所有这些 PUT/PATCH/POST/DELETE 问题。