JPA：Select parent 和 child 具有一对多关系

Question

实现了一对多关系 select parent 和 child 我有 onetomany 关系，我想查询 (select *)

Folders.java

@Entity
@Table(name = "FOLDERS")
public class Folders implements Serializable {
    @Id
    @Column(name = "id")
    Long id;
    @ManyToOne
    @JoinColumn(name = "Folder_Author", insertable=false, updatable=false)
    private Authors author;
    // Getter + setter
}

Authors.java

@Entity
@Table(name = "AUTHORS")
public class Authors implements Serializable {

    @Id
    @Column(name = "id")
    Long id;
    @OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.PERSIST)
    @JoinColumn(name = "Folder_Author", referencedColumnName = "id", nullable=false)
    private List<Folders> folders = new ArrayList<Folders>();
}

我的要求：

Query query = em.createQuery("SELECT f FROM Folders f");
return query.getResultList();

我得到了这个结果：

[
    {   
        "id":29,
        "noFolder":"0017",
        "author":{
            "id":9,
            "name":"Alpha",
            "service":null,
            "folders":[
                {"id":29,
                "noFolder":"0017",
                "author":{
                    "id":9,
                    "name":"Alpha",
                    "service":null,
                    "folders":[
                    {
                        "id":29,
                        "noFolder":"0017",
                        "author":{
                        "id":9,
                        "name":"Alpha",
                        "service":null,
                        "folders":[
                            ..
                            ..
            }
]

我的代码有什么问题？当我执行查询时出现什么问题我得到了这个结果.. .. 我想得到这个结果

[
    {   
        "id":29,
        "noFolder":"0017",
        "author":{
            "id":9,
            "name":"Alpha",
            "service":null,
            }
    }
]

Answer 1

只需在 collection 字段中使用 @JsonIgnore，如下所示：

@OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.PERSIST)
    @JoinColumn(name = "Folder_Author", referencedColumnName = "id", nullable=false)
    @JsonIgnore
    private List<Folders> folders = new ArrayList<Folders>();

Answer 2

在作者的文件夹列表上使用@JsonBackReference class 以防止递归序列化。

另见

JPA：Select parent 和 child 具有一对多关系

JPA : Select parent and child with oneToMany relatinships

hibernate

jpa

hibernate-mapping

hibernate-onetomany