Java 如何删除多对多关系（Spring jpa rest app）中的子实体而不删除父实体？

我在专家和标签之间有一种多对多的关系。我想允许用户删除专家包含的一个标记，而不删除整个专家实体。现在我总是删除一个tagIi get all expert也删除了

我的spring jpa应用程序控件按id删除标记的方法：

 @DeleteMapping("/tags/{id}")
    public ResponseEntity<Void> deleteTagById(@PathVariable Long id){
        log.debug("REST request to delete a tag by Id{} ", id);
        return tagService.deleteById(id);
    }

@Entity
@Table(name="tags")
public class Tag {

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

    @ManyToMany(mappedBy="tags", cascade = {CascadeType.ALL})
    private List<Expert> experts = new ArrayList<>();

    public Tag() {
    } //getters and setters

@Entity
@Table(name="experts")
public class Expert {

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

    private String name;
    private String surname;
    private String dni;
    private String address;
    private String mail;
    private String phone;
    private String linkedln;
    private String state;
    private String rating;
    private String availability;
    
    @ManyToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(
            name = "experts_tags",
            joinColumns = {@JoinColumn(name="tags_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name="experts_id", referencedColumnName = "id")}
    )
    private List<Tag> tags = new ArrayList<>();


    public Expert() {
    } //getters and setters

@DeleteMapping（“/tags/{id}”）
公共响应性deleteTagById（@PathVariable Long id）{
debug（“按Id{}，Id删除标记的REST请求）；
return tagService.deleteById（id）；
}

我的标签型号：

 @DeleteMapping("/tags/{id}")
    public ResponseEntity<Void> deleteTagById(@PathVariable Long id){
        log.debug("REST request to delete a tag by Id{} ", id);
        return tagService.deleteById(id);
    }

@Entity
@Table(name="tags")
public class Tag {

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

    @ManyToMany(mappedBy="tags", cascade = {CascadeType.ALL})
    private List<Expert> experts = new ArrayList<>();

    public Tag() {
    } //getters and setters

@Entity
@Table(name="experts")
public class Expert {

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

    private String name;
    private String surname;
    private String dni;
    private String address;
    private String mail;
    private String phone;
    private String linkedln;
    private String state;
    private String rating;
    private String availability;
    
    @ManyToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(
            name = "experts_tags",
            joinColumns = {@JoinColumn(name="tags_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name="experts_id", referencedColumnName = "id")}
    )
    private List<Tag> tags = new ArrayList<>();


    public Expert() {
    } //getters and setters

@实体
@表（name=“tags”）
公共类标签{
@身份证
@GeneratedValue（策略=GenerationType.IDENTITY）
私人长id；
私有字符串名称；
@ManyToMany（mappedBy=“tags”，cascade={CascadeType.ALL}）
私有列表专家=新的ArrayList（）；
公共标签（）{
}//getter和setter

我的专家模型：

 @DeleteMapping("/tags/{id}")
    public ResponseEntity<Void> deleteTagById(@PathVariable Long id){
        log.debug("REST request to delete a tag by Id{} ", id);
        return tagService.deleteById(id);
    }

@Entity
@Table(name="tags")
public class Tag {

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

    @ManyToMany(mappedBy="tags", cascade = {CascadeType.ALL})
    private List<Expert> experts = new ArrayList<>();

    public Tag() {
    } //getters and setters

@Entity
@Table(name="experts")
public class Expert {

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

    private String name;
    private String surname;
    private String dni;
    private String address;
    private String mail;
    private String phone;
    private String linkedln;
    private String state;
    private String rating;
    private String availability;
    
    @ManyToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(
            name = "experts_tags",
            joinColumns = {@JoinColumn(name="tags_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name="experts_id", referencedColumnName = "id")}
    )
    private List<Tag> tags = new ArrayList<>();


    public Expert() {
    } //getters and setters

@实体
@表（name=“专家”）
公开课专家{
@身份证
@GeneratedValue（策略=GenerationType.IDENTITY）
私人长id；
私有字符串名称；
私家姓；
私有字符串dni；
私有字符串地址；
私人字符串邮件；
私人电话；
私有字符串链接；
私有字符串状态；
私人字符串评级；
私有字符串可用性；
@ManyToMany（fetch=FetchType.EAGER，cascade={CascadeType.ALL}）
@可接合(
name=“专家标签”，
joinColumns={@JoinColumn（name=“tags\u id”，referencedColumnName=“id”）}，
inverseJoinColumns={@JoinColumn（name=“experts\u id”，referencedColumnName=“id”）}
)
private List tags=new ArrayList（）；
公共专家（）{
}//getter和setter

到目前为止我尝试了什么：

 @DeleteMapping("/tags/{id}")
    public ResponseEntity<Void> deleteTagById(@PathVariable Long id){
        log.debug("REST request to delete a tag by Id{} ", id);
        return tagService.deleteById(id);
    }

@Entity
@Table(name="tags")
public class Tag {

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

    @ManyToMany(mappedBy="tags", cascade = {CascadeType.ALL})
    private List<Expert> experts = new ArrayList<>();

    public Tag() {
    } //getters and setters

@Entity
@Table(name="experts")
public class Expert {

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

    private String name;
    private String surname;
    private String dni;
    private String address;
    private String mail;
    private String phone;
    private String linkedln;
    private String state;
    private String rating;
    private String availability;
    
    @ManyToMany(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinTable(
            name = "experts_tags",
            joinColumns = {@JoinColumn(name="tags_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name="experts_id", referencedColumnName = "id")}
    )
    private List<Tag> tags = new ArrayList<>();


    public Expert() {
    } //getters and setters

此方法有效地删除了标签，但也删除了专家：

public ResponseEntity<Void> deleteTag(Long id) {
        Tag tag=this.manager.find(Tag.class,id);
        this.manager.remove(tag);
        return ResponseEntity.noContent().build();

public ResponseEntity deleteTag（长id）{
Tag Tag=this.manager.find（Tag.class，id）；
此.manager.remove（标记）；
返回ResponseEntity.noContent（）.build（）；

我试图避免此方法返回500错误：

public ResponseEntity<Void> deleteTagById(Long id) {
        Expert expert = (Expert) manager.createQuery("SELECT  Expert from Tag u where u.id = :id");

        for(Tag tag : expert.getTags()){
            if (tag.getId() == id){
                expert.getTags().remove(tag);
                manager.persist(expert);
            }
        }
        return ResponseEntity.noContent().build();

    }
}

    }

public ResponseEntity deleteTagById（长id）{
Expert=（Expert）manager.createQuery（“从标记u中选择专家，其中u.id=：id”）；
for（标记：expert.getTags（））{
if（tag.getId（）==id）{
expert.getTags（）.remove（标记）；
经理。坚持（专家）；
}
}
返回ResponseEntity.noContent（）.build（）；
}
}
}

---

有人能帮我吗？我很感激任何建议：）谢谢！

这是因为你定义所有的行动都应该传达给专家：

@ManyToMany(mappedBy="tags", cascade = {CascadeType.ALL})
private List<Expert> experts = new ArrayList<>();

@ManyToMany（mappedBy=“tags”，cascade={CascadeType.ALL}）
私有列表专家=新的ArrayList（）；

---

不要使用

ALL

，而应该列出实际要级联的内容。

在

标记中没有名为
Expert
的属性