Question

我目前面临以下问题：我在countries和cities之间存在关联。正如您可能想象的那样，这种关系非常简单，country可以有多个cities，而city只属于一个country。删除country后，我希望将所有权cities保留在我的数据库中。

我的域名模型如下所示：

班级国家/地区：

@Entity
@Table( name = "COUNTRIES" )
public class Country extends BaseEntity {
    private String name;
    private Set< City > cities = new HashSet<>();

    @Column( name = "NAME", length = 80, nullable = false, unique = true )
    public String getName() {
        return name;
    }

    public void setName( String name ) {
        this.name = name;
    }

    @OneToMany( fetch = FetchType.LAZY, mappedBy = "country", cascade = CascadeType.ALL )
    public Set< City > getCities() {
        return cities;
    }

    public void setCities( Set< City > cities ) {
        this.cities = cities;
    }
}

班级城市：

@Entity
@Table( name = "CITIES" )
public class City extends BaseEntity {

    private String  name;
    private Country country;

    @Column( name = "NAME", length = 120, nullable = false )
    public String getName() {
        return name;
    }

    public void setName( String name ) {
        this.name = name;
    }

    @ManyToOne( fetch = FetchType.LAZY )
    @JoinColumn( name = "COUNTRY_ID", nullable = true )
    public Country getCountry() {
        return country;
    }

    public void setCountry( Country country ) {
        this.country = country;
    }
}

仅为了您的信息，BaseEntity只保留主键以及创建或修改实体时的信息。

如果从数据库中删除某个国家/地区，我如何才能删除我的城市？

Answer 1

替换cascade = CascadeType.ALL

与

cascade = { CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH }

在

 @OneToMany( fetch = FetchType.LAZY, mappedBy = "country", cascade = CascadeType.ALL )
    public Set< City > getCities() {
        return cities;
    }

删除父项时保留子项

1 个答案: