java - JPA2 : Nested Primary Key class cannot persist as binding null

Question

我将 JPA 2.x 与 EclipseLink 2.5.1 一起使用，并使用嵌套主键类，如下所示:-

注意:幕后环境

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
}

详细信息

@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
}

保存详细信息的编码

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>

项目启动时，所有表都已正确创建，尤其是主键和外键。但是，当坚持编码时，Detail会出现一些问题，因为Detail.masterId.id为空。 EclipseLink 将我显示为

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))
                                            )
                                )
                         )

我通过打印此对象图中的所有字段来仔细检查，并可以确认masterId也不为空。我不确定是否做错了什么/误解。您能帮忙建议一下如何解决这个问题吗？

编辑 1

1. 修复 Detail.java 处的 @ManyToOne。复制粘贴到此问题时出现拼写错误

2. 尝试将 @Embedded 添加到 DetailPk 类的 masterId。

   编辑 1 个结果仍然面临同样的问题。

编辑2

1. 添加用于创建详细信息和持久的代码

2. 我直接创建了MasterPk而没有找到Master。

   进一步的问题，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，因此应使用 @Embedded 进行注释:

@Embeddable
public class DetailPk {

    @Embedded
    private MasterPk masterId;
    ...
}

我猜Detail实体也缺少@ManyToOne(或者这只是故意的？)

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

<小时/>

广告编辑 2

以下声明

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

表示主从关系的拥有方(由@ManyToOne关联表示)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 实体引用带有 master 字段的 Master
• 由于 Detail 实体充当关系的所有者，因此最好在其上指定级联，即 @ManyToOne(cascade = CascadeType.PERSIST)

根据上述内容，为了使事情正常进行，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]