Google app engine JPA，类的元数据错误：多个主键字段

我有一个家长和一个孩子班。运行应用程序时，我遇到以下错误：

Error in meta-data for com.twitterjaya.model.HistoryDeviceJPA: More than one primary key field.

我不知道为什么它说我定义了不止一个主键。如有任何建议，将不胜感激

@Entity(name = "HistoryJPA")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@DiscriminatorValue("HistoryJPA")
public class HistoryJPA {

    @Id
    String pageAddress;
    String domain;
    String pageTitle;
    long pageVisits;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        HistoryJPA that = (HistoryJPA) o;

        if (!pageAddress.equals(that.pageAddress)) return false;

        return true;
    }

    @Override
    public int hashCode() {
        return pageAddress.hashCode();
    }

    @Override
    public String toString() {
        return "HistoryJPA{" +
                "pageAddress='" + pageAddress + '\'' +
                ", domain='" + domain + '\'' +
                ", pageTitle='" + pageTitle + '\'' +
                ", pageVisits=" + pageVisits +
                '}';
    }

    public String getPageAddress() {
        return pageAddress;
    }

    public void setPageAddress(String pageAddress) {
        this.pageAddress = pageAddress;
    }

    public String getDomain() {
        return domain;
    }

    public void setDomain(String domain) {
        this.domain = domain;
    }

    public String getPageTitle() {
        return pageTitle;
    }

    public void setPageTitle(String pageTitle) {
        this.pageTitle = pageTitle;
    }

    public long getPageVisits() {
        return pageVisits;
    }

    public void setPageVisits(long pageVisits) {
        this.pageVisits = pageVisits;
    }
}

儿童班：

@Entity(name = "HistoryDeviceJPA")
@DiscriminatorValue("HistoryDeviceJPA")
public class HistoryDeviceJPA extends HistoryJPA {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String userUUID;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        if (!super.equals(o)) return false;

        HistoryDeviceJPA that = (HistoryDeviceJPA) o;

        if (!id.equals(that.id)) return false;
        if (!userUUID.equals(that.userUUID)) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = super.hashCode();
        result = 31 * result + id.hashCode();
        result = 31 * result + userUUID.hashCode();
        return result;
    }

    @Override
    public String toString() {
        return "HistoryDeviceJPA{" +
                "id=" + id +
                ", userUUID='" + userUUID + '\'' +
                '}';
    }

    public String getUserUUID() {
        return userUUID;
    }

    public void setUserUUID(String userUUID) {
        this.userUUID = userUUID;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }
}

---

如错误消息所述，您有两个主键（用

@Id

注释）：

• 在

  HistoryJPA

  字段

  pageAddress

• 字段

  id

---

您应该去掉其中一个，或者根据您的需要创建一个新文档。

谢谢，我发现此文档也很有用：