如何使用oneToMany映射ModelMapper

Question

我正在使用springBoot，我想映射OneToMany从父母到孩子的关系。直接使用entity和eager获取，我得到递归记录，因此，尝试使用ModelMapper到Entity的DTO映射，但我无法弄清楚如何做到这一点。请假设getters和setters。

Parent.java

@Entity
public class Parent {

    @Id
    private int parentId;

    private String a;

    @OneToMany(mappedBy = "parent")
    private Set<Child> child;

Child.java

@Entity
public class Child {

    @Id
    private int childId;

    private String c;

    @ManyToOne
    @JoinColumn(name = "b")
    private Parent parent;

我有使用findAll方法的工作存储库和服务程序。

ParentDto.java

public class ParentDto {

    private String a;

    private Set<Child> child;

ParentController.java

@RestController
public class ParentController {

    @Autowired
    private ModelMapper modelMapper;

    @Autowired
    private ParentService parentService;


    @RequestMapping(method = RequestMethod.GET, value="/parents" )
    public List<ParentDto> getParents() {
        List<Parent> parents =  parentService.getAll();
        return parents.stream()
                .map(x-> modelMapper.map(x, ParentDto.class))
                .collect(Collectors.toList());
    }
}

错误:尝试获取http://localhost:8080/parents时的

.
.
ModelMapper mapping errors: 1) Converter org.modelmapper.internal.converter.CollectionConverter@51381583 failed to convert java.util.Set to java.util.Set. 1 error
org.modelmapper.MappingException: ModelMapper mapping errors:

1) Converter org.modelmapper.internal.converter.CollectionConverter@51381583 failed to convert java.util.Set to java.util.Set.

1 error
    at org.modelmapper.internal.Errors.throwMappingExceptionIfErrorsExist(Errors.java:380)
    at org.modelmapper.internal.MappingEngineImpl.map(MappingEngineImpl.java:80)
.
.

Answer 1

这与“N+1”和“无限递归”问题无关，可以将Conver方法添加到映射程序中；用ModelMapper https://amydegregorio.com/2018/10/03/mapping-children-with-modelmapper/映射儿童

Answer 2

我建议“首选嵌套属性”。

http://modelmapper.org/user-manual/configuration

Answer 3

您需要在您的子实体中定义的父映射上使用@JsonIgnore注释。

有关更多信息- https://fasterxml.github.io/jackson-annotations/javadoc/2.5/com/fasterxml/jackson/annotation/JsonIgnore.html，请参阅本文档。