使用 MapStruct 转换时的循环引用。溢出错误。上下文不起作用

Question

我有 2 个实体，具有一对一关联（ProfileEntity 和 VCardEntity）

实体电子名片：

@Entity
@Table(name = "vcard")
@AllArgsConstructor
@NoArgsConstructor
@Data
@SequenceGenerator(name="vcard_id_seq_generator", sequenceName="vcard_id_seq", allocationSize = 1)
public class VCardEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "vcard_id_seq_generator")
    @Column(name="vcard_id")
    Long id;
    String account;
    @Column(name = "first_name")
    String firstName;
    @Column(name = "last_name")
    String lastName;
    @Column(name = "pbxinfo_json")
    String pbxInfoJson;
    @Column(name = "avatar_id")
    String avatarId;
    @OneToOne(mappedBy = "vcard")
    ProfileEntity profile;
}

实体简介：

@Entity
@AllArgsConstructor
@NoArgsConstructor
@Data
@Table(name = "profile")
public class ProfileEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "profile_id")
    private Long profileId;

    private String account;
    @Column(name = "product_id")
    private String productId;
    
    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "vcard_id", referencedColumnName = "vcard_id")
    private VCardEntity vcard;
}

我使用 map 结构如下：

public class CycleAvoidingMappingContext {
    private Map<Object, Object> knownInstances = new IdentityHashMap<Object, Object>();

    @BeforeMapping
    public <T> T getMappedInstance(Object source, @TargetType Class<T> targetType) {
        return targetType.cast(knownInstances.get(source));
    }
    
    @BeforeMapping
    public void storeMappedInstance(Object source, @MappingTarget Object target) {
        knownInstances.put( source, target );
    }
}

@Mapper(componentModel = "spring")
public interface EntityToProfile {
    ProfileEntity profileToEntity(Profile profile, @Context CycleAvoidingMappingContext context);
    Profile entityToProfile(ProfileEntity entity, @Context CycleAvoidingMappingContext context);
}

@Mapper(componentModel = "spring")
public interface EntityToVCard {
    VCard entityToVcard(VCardEntity entity, @Context CycleAvoidingMappingContext context);
    VCardEntity vcardToEntity(VCard vcard, @Context CycleAvoidingMappingContext context);
}

最后我在我的服务中调用映射：

@Service
@RequiredArgsConstructor
@Slf4j
public class DefaultChatService implements ChatService {
    private final ProfileRepository profileRepository;
    private final EntityToProfile entityToProfileMapper;
    private final EntityToVCard entityToVCardMapper;

    @Override
    public List<Profile> findAllProfile(Optional<Long> id) {
        if (id.isPresent()) {
            Optional<ProfileEntity> result = profileRepository.findById(id.get());
            if (result.isPresent()) {
                Profile profile = entityToProfileMapper.entityToProfile(result.get(), new CycleAvoidingMappingContext());
                return Stream.of(profile).collect(Collectors.toList());
            }
        }
        return new ArrayList<Profile>();
    }
}

我得到了错误 ERROR 15976 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]：Servlet.service() 用于路径 [] 上下文中的 servlet [dispatcherServlet] 引发异常 [Handler发送失败；嵌套异常是 java.lang.StackOverflowError] 的根本原因 java.lang.StackOverflowError: null

有什么想法可以解决吗？ 在我看来，我所做的一切都是在这里写的 Prevent Cyclic references when converting with MapStruct 但它对我不起作用

Answer 1

找到了解决方案，我所要做的就是将我的模型从 @Value 更改为 @Data

给出的例子：

@Data
public class Profile {
    Long profileId;
    String account;
    String productId;
    VCard vcard;
}

和

@Data
public class VCard {
    Long id;
    String account;
    String firstName;
    String lastName;
    String pbxInfoJson;
    String avatarId;
    Profile profile;
}

否则 mapstruct 无法生成正确的映射代码。它试图在创建对象后将实例存储在 knownInstances 中，例如 Profile。但是因为 @value 在创建对象（不可变对象）后没有提供设置属性的方法，所以它必须先创建所有设置，然后使用所有 args 构造函数，这首先导致映射配置文件，而后者又试图做同样的事情并在将 VCard 对象存储在 knownInstances 中之前先映射 vcard。 这就是循环引用问题无法解决的原因

正确生成的代码：

public Profile entityToProfile(ProfileEntity entity, CycleAvoidingMappingContext context) {
        Profile target = context.getMappedInstance( entity, Profile.class );
        if ( target != null ) {
            return target;
        }

        if ( entity == null ) {
            return null;
        }

        Profile profile = new Profile();

        context.storeMappedInstance( entity, profile );

        profile.setAccount( entity.getAccount() );
        profile.setProductId( entity.getProductId() );
        profile.setDeviceListJson( entity.getDeviceListJson() );
        profile.setLastSid( entity.getLastSid() );
        profile.setBalanceValue( entity.getBalanceValue() );
        profile.setBalanceCurrency( entity.getBalanceCurrency() );
        profile.setStatusJson( entity.getStatusJson() );
        profile.setData( entity.getData() );
        profile.setMissedCallsCount( entity.getMissedCallsCount() );
        profile.setFirstCallSid( entity.getFirstCallSid() );
        profile.setLastMissedCallSid( entity.getLastMissedCallSid() );
        profile.setRemoveToCallSid( entity.getRemoveToCallSid() );
        profile.setOutgoingLines( entity.getOutgoingLines() );
        profile.setFeatures( entity.getFeatures() );
        profile.setPermissions( entity.getPermissions() );
        profile.setVcard( vCardEntityToVCard( entity.getVcard(), context ) );

        return profile;
    }
}

如您所见，首先，它将对象保存在 context.storeMappedInstance( entity, profile );然后填充属性。