Question

在很多情况下，我必须维护/改进旧系统。例子

create table COMPANY(
    COMP_ID_COMPANY NUMBER(10),
    COMP_NAME VARCHAR(32),
    /*... MANY FIELDS*/
    PRIMARY KEY (COMP_ID_COMPANY)
);

create table BUSINESS_UNIT(
    BUZZ_ID_COMPANY NUMBER(10),
    BUZZ_ID_BUZZUNIT NUMBER(10),
    /*... MANY FIELDS*/
    PRIMARY KEY (BUZZ_ID_COMPANY, BUZZ_ID_BUZZUNIT),
    CONSTRAINT FK_BUZZ_COMP FOREIGN KEY (BUZZ_ID_COMPANY) REFERENCES COMPANY (COMP_ID_COMPANY)
)

create table BRANCH(
    BRAN_ID_COMPANY NUMBER(10),
    BRAN_ID_BRANCH NUMBER(10),
    BRAN_NAME VARCHAR(32),
    /*... MANY FIELDS*/
    BRAN_ID_BUZZUNIT NUMBER(10) nullable, /*HERE IS THE PROBLEM*/
    PRIMARY KEY (BRAN_ID_COMPANY, BRAN_ID_BRANCH),
    CONSTRAINT FK_BRAN_BUZZ FOREIGN KEY (BRAN_ID_COMPANY, BRAN_ID_BUZZUNIT) REFERENCES BUSINESS_UNIT (BUZZ_ID_COMPANY, BUZZ_ID_BUZZUNIT) /*HERE IS THE PROBLEM*/
);

前两个单元的映射很简单，我必须为COMPANY PK创建一个类，并使用@EmbeddedId和@Embeddable进行注释。但是，在Branch类上，我有这个问题

@Embeddable
class BranchPk{
    @Column(name="BRAN_ID_COMPANY")
    private Long branIdCompany;
    @Column(name="BRAN_ID_BRANCH")
    private Long branIdBranch;
}

@Entity
@Table(name="BRANCH"
class Branch {
    @EmbeddedId
    private BranchPk pk;

    @ManyToOne 
    @JoinColumns({
        @JoinColumn(name="BRAN_ID_COMPANY", insertable=false, updatable=false), //I cannot keep this field insertable or updatable because makes part of the primary key
        @JoinColumn(name="BRAN_ID_BUZZUNIT"), //JPA doesn't allow me to mix the insertable/updatable fields with noninsertable/nonupdatable ones
    })
    private BusinessUnit businessUnit;
}

问题是：如何映射允许businessUnit属性为null且不从PK删除branIdCompany的此类？我希望仅使用JPA来解决此问题，但是使用休眠特定性对我来说不是问题。

当我在主键中共享了列（但不仅是）时，如何映射jpa实体

0 个答案: