JPA2:嵌套主键类不能作为绑定null持久化

Question

我将JPA 2.x与EclipseLink 2.5.1与nested primary key class一起使用，具体如下：

注:场景背后的环境

1. OS: Windows 7 64 Bits
2. JDK: 1.7.0_65 64 Bits
3. Maven: 3.2.2
4. Arquillian: 1.1.5.Final
5. Container: Glassfish 4 embedded
6. Database: Derby 10.10.2.0 embedded

大师PK

@Embeddable
public class MasterPk {
    @Column(
        name   = "MASTER_ID",
        length = 5
    )
    private String masterId;

    //----> Setter/Getter is omitted
}

大师

@Entity
@Table(name = "MASTER_TAB")
public class Master {

    @EmbeddedId
    private MaskerPk id;

    @Column(
        name   = "MASTER_NAME",
        length = 40
    )
    private String masterName;

    @OneToMany(
        mappedBy = "master"
    )
    private List<Detail> details;

    //----> Setter/Getter is omitted
}

细节PK

@Embeddable
public class DetailPk {

    //----> THE NESTED IS HERE.
    @Embedded
    private MasterPk masterId;

    @Column(
        name   = "DETAIL_ID",
        length = 5
    )
    private String detailId;

    //----> Setter/Getter is omitted
}

细节

@Entity
@Table(name = "DETAIL_TAB")
public class Detail {

    @EmbeddedId
    private DetailPk id;

    @Column(
        name   = "DETAIL_NAME",
        length = 40
    )
    private String detailName;

    @MapsId("masterId")
    @ManyToOne
    @JoinColumns({
        @JoinColumn(
            name                 = "MASTER_ID",
            referencedColumnName = "MASTER_ID",
            nullable             = false
        )
    })
    private Master master;

    //----> Setter/Getter is omitted
}

持久化细节编码

MasterPk masterPk = new MasterPk();
masterPk.setId("001"); //there is a 001 existed in the db

DetailPk detailPk = new DetailPk();
detailPk.setMasterId(masterPk);
detailPk.setDetailId("001"); //new detail to persist

Detail detail = new Detail();
detail.id(detailPk);
detail.setDetailName("detail-name");

em.persist(detail);

持久性XML

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence 
                   http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"
             version="2.1">
    <persistence-unit name="unittest" transaction-type="JTA">

        <jta-data-source>jdbc/unittest</jta-data-source>

        <class>com.test.MasterPk</class>
        <class>com.test.Master</class>
        <class>com.test.DetiailPk</class>
        <class>com.test.Detail</class>

        <exclude-unlisted-classes>true</exclude-unlisted-classes>

        <properties>
            <property name="eclipselink.ddl-generation" 
                      value="create-tables" />                     
            <property name="eclipselink.ddl-generation.output-mode"
                      value="both"/>
            <property name="eclipselink.application-location" 
                      value="target"/>                     
            <property name="eclipselink.create-ddl-jdbc-file-name" 
                      value="createDDL_ddlGeneration.jdbc"/>
            <property name="eclipselink.drop-ddl-jdbc-file-name" 
                      value="dropDDL_ddlGeneration.jdbc"/>
        </properties>

    </persistence-unit>
</persistence>

当项目启动时，所有表都会正确创建，特别是primary key和foreign key。但是，当persist进行编码时，Detail会出现一些问题，因为Detail.masterId.id是空的。EclipseLink向我展示了

Column 'MASTER_ID' cannot accept a NULL value.

INSERT INTO DETAIL_TAB (DETAILE_NAME, DETAIL_ID, MASTER_ID)
VALUES (?, ?, ?)
bind => [detail-name, 001, null]

//
//----> We may be noticed that the masterId is not null. It is printed as 001.
//
Query: InsertObjectQuery(Detail(detailName=detail-name,
                                id=DetailPk(detailId=001,
                                            masterId=(MasterPk(masterId=001))
                                            )
                                )
                         )

我通过在此field中打印所有object-graph来进行双重检查，并且可以确认masterId也不是null。我不确定是否做错了什么/误解了什么。你能帮我建议如何解决这个问题吗？

编辑1

1. 修复@ManyToOne在Detail.java上。在复制和粘贴这个问题时，这是一个错误。
2. 尝试将@Embedded添加到类DetailPk的masterId中。 编辑1结果仍然面临相同的问题。

编辑2

1. 添加用于创建detail和persist的代码
2. 我直接创建MasterPk，而没有找到Master。 进一步的问题是，我是否需要找到Mater实体来获取其id并将其分配给DetailPk，而不是直接通过new MasterPk();创建它？

Answer 1

由于MasterPK是可嵌入的，所以应该用@Embedded对其进行注释

@Embeddable
public class DetailPk {

    @Embedded
    private MasterPk masterId;
    ...
}

我猜Detail实体也缺少@ManyToOne (还是故意的？)

@Entity
@Table(name = "DETAIL_TAB")
public class Detail {
    ...
    @MapsId("masterId")
    @ManyToOne
    @JoinColumns({
        @JoinColumn(
            name                 = "MASTER_ID",
            referencedColumnName = "MASTER_ID",
            nullable             = false
        )
    })
    private Master master;
}

Ad 编辑2

以下陈述

INSERT INTO DETAIL_TAB (DETAILE_NAME, DETAIL_ID, MASTER_ID)
VALUES (?, ?, ?)
bind => [detail-name, 001, null]

意味着主细节关系(由@ManyToOne关联表示)的拥有方为空。从JPA的角度来看，这看起来如下：

• MASTER_ID列与Detail实体中的master字段相关。
• Master实体使用MasterPK作为主键
• Detail实体使用master字段引用Master
• 因为Detail实体充当关系的所有者，所以最好在其上指定级联，即@ManyToOne(cascade = CascadeType.PERSIST)。

基于以上所述，为了使事物正常工作，我们需要设置拥有方，例如：

Master master = new Master();
master.id(masterPk);    

Detail detail = new Detail();
detail.id(detailPk);
detail.setMaster(master); // the owning side of the master-detail relationship

master.setDetail(detail); // mandatory if CascadeType.PERSIST is not defined
em.persist(detail);

这将导致：

INSERT INTO DETAIL_TAB (DETAIL_NAME, DETAIL_ID, MASTER_ID)
VALUES (?, ?, ?)
bind => [detail-name, 001, 001]