使用@IdClass转换实体中的请求元素失败

Question

我有以下设置:

@Entity
@IdClass(MemberAttributePk.class)
public class MemberAttribute {
    @Id
    @ManyToOne @JoinColumn(name="member_id")
    protected Member member;
    @Id
    protected String name;
    private String value;
    public MemberAttribute() {}
    // get & set
}

和id类:

public class MemberAttributePk implements Serializable {
    protected Member member;
    protected String name;
    public MemberAttributePk() {}
    // get & set
}

我已经为MemberAttribute定义了一个简单的Spring Data存储库:

@Repository
public interface MemberAttributeRepo extends JpaRepository<MemberAttribute, MemberAttributePk> {
}

现在，我要做的就是将一个成员属性持久化到数据库:

public void saveAttribute(Member member, String name, String value) {
    MemberAttribute attr = new MemberAttribute(member, name, value);
    attributeRepo.save(attr);
}

但是，我最终得到了这个服务器异常:

2016-08-28 00:24:20.673  WARN 5656 --- [nio-8080-exec-8] .w.s.m.s.DefaultHandlerExceptionResolver : 
Failed to convert request element: org.springframework.beans.ConversionNotSupportedException: 
Failed to convert property value of type [java.lang.Long] to required type [com.example.Member] for property 'member'; nested exception is java.lang.IllegalStateException: 
Cannot convert value of type [java.lang.Long] to required type [com.example.Member] for property 'member': 
no matching editors or conversion strategy found

你知道我做错了什么吗?谢谢!

Answer 1

您的代码不兼容JPA。问题的原因是您使用Member作为您PK的一部分。 PK只能由以下Java类型的字段组成

1. 原语: boolean, byte, char, int, long, short
2. java。lang: Boolean, Byte, Character, Integer, Long, Short, String, Enum, StringBuffer
3. java。math: BigInteger java。sql:日期，时间，时间戳
4. java。util:日期，货币，地区，时区，UUID
5. java.net: URI, URL
6. javax.jdo。spi: PersistenceCapable

---

这个应该可以工作:

@Embeddable
public class MemberAttributePk implements Serializable {
    @Column(name = "member_id")
    protected Long memberId;
    @Column(name = "name")
    protected String name;
    public MemberAttributePk() {}
    // get & set
}
@Entity
public class MemberAttribute {
    @EmbeddedId
    protected MemberAttributePk memberAttributePk;
    @ManyToOne 
    @JoinColumn(name="member_id")
    protected Member member;
    private String value;
    public MemberAttribute() {}
    // get & set
}

或与@ClassId

相同

public class MemberAttributePk implements Serializable {
    protected Long memberId;
    protected String name;
    public MemberAttributePk() {}
    // get & set
}
@Entity
@IdClass(MemberAttributePk.class)
public class MemberAttribute {
    @Id
    @Column(name = "member_id")
    protected Long memberId;
    @Id
    @Column(name = "name")
    protected String name;
    @ManyToOne 
    @JoinColumn(name="member_id")
    protected Member member;
    private String value;
    public MemberAttribute() {}
    // get & set
}

Answer 2

您可以尝试使用MemberRepository保存它，因为我相信您的Member类和MemberAttribute类有一对多的关系引用，下面是示例

成员类

@Entity
public class Member {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long id;
    @OneToMany(mappedBy = "Member", cascade = CascadeType.ALL)
     private Set<MemberAttribute> mMemberAttributes = new HashSet<>();
     public void setMemberAttributes(Set<MemberAttribute> mMemberAttributes){
        this.mMemberAttributes = mMemberAttributes;
     }
     public Set<MemberAttribute> getMemberAttributes(){
         return mMemberAttributes;
     }
     // other code
}

MemberRepository类

public interface MemberRepository extends JpaRepository<Member, Long> {
}

保存函数中的代码

public void saveAttribute(Member member, String name, String value) {
    MemberAttribute attr = new MemberAttribute(member, name, value);
    member.getMemberAttributes().add(attr);
    memberRepository.save(member);
}