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EntitIEs
实体必须实现IDentifiable接口。例如：
@Entity
public class category implements IDentifiable<Integer> {
@ID
@GeneratedValue
private final Integer ID;
private final String name;
@OnetoMany
private final Set<Product> products = new HashSet<>();
// skipped
}
@Entity
public class Product implements IDentifiable<Integer> {
@ID
@GeneratedValue
private final Integer ID;
private final String name;
// skipped
}
创建一个投影接口，存储库查询方法将返回：
public interface categoryProjection {
category getcategory();
Long getQuantity();
}
这将是DTO的基础。在此示例中，DTO将代表a category，而Products 的数量属于它。
Repository methods
Create方法将返回投影：一个投影，一个DTO列表和一个DTO页面列表。
@RepositoryRestresource
public interface categoryRepo extends JpaRepository<category, Integer> {
@Restresource(exported = falsE)
@query("SELEct c as category, count(p) as quantity from category c join c.products p where c.ID = ?1 group by c")
categoryProjection getDto(Integer categoryID);
@Restresource(exported = falsE)
@query("SELEct c as category, count(p) as quantity from category c join c.products p group by c")
List<categoryProjection> getDtos();
@Restresource(exported = falsE)
@query("SELEct c as category, count(p) as quantity from category c join c.products p group by c")
Page<categoryProjection> getDtos(Pageable pageablE);
}
DTO
从其接口实施DTO：
@Relation(value = "category", collectionRelation = "categorIEs")
public class categoryDto implements categoryProjection {
private final category category;
private final Long quantity;
// skipped
}
Relation当Spring Data REST渲染对象时使用注释。
控制者
向RepositoryRestController其中添加自定义方法将满足DTO的请求：
@RepositoryRestController
@requestMapPing("/categorIEs")
public class categoryController {
@autowired private categoryRepo repo;
@autowired private RepositoryEntitylinks links;
@autowired private PagedresourcesAssembler<categoryProjection> assembler;
/**
* Single DTO
*/
@GetMapPing("/{ID}/dto")
public ResponseEntity<?> getDto(@PathVariable("ID") Integer categoryID) {
categoryProjection dto = repo.getDto(categoryID);
return ResponseEntity.ok(toresource(dto));
}
/**
* List of DTO
*/
@GetMapPing("/dto")
public ResponseEntity<?> getDtos() {
List<categoryProjection> dtos = repo.getDtos();
link ListSelflink = links.linkFor(category.class).slash("/dto").withSelfRel();
List<?> resources = dtos.stream().map(this::toresourcE).collect(toList());
return ResponseEntity.ok(new resources<>(resources, ListSelflink));
}
/**
* Paged List of DTO
*/
@GetMapPing("/dtopaged")
public ResponseEntity<?> getDtosPaged(Pageable pageablE) {
Page<categoryProjection> dtos = repo.getDtos(pageablE);
link pageSelflink = links.linkFor(category.class).slash("/dtopaged").withSelfRel();
Pagedresources<?> resources = assembler.toresource(dtos, this::toresource, pageSelflink);
return ResponseEntity.ok(resources);
}
private resourceSupport toresource(categoryProjection projection) {
categoryDto dto = new categoryDto(projection.getcategory(), projection.getQuantity());
link categorylink = links.linkForSingleresource(projection.getcategory()).withRel("category");
link selflink = links.linkForSingleresource(projection.getcategory()).slash("/dto").withSelfRel();
return new resource<>(dto, categorylink, selflink);
}
}
从存储库收到projections时，我们必须先完成从Projection到DTO的转换，然后将其“包装”到resourceSupport对象，然后再发送给客户端。为此，我们使用辅助方法toresource：创建一个新的DTO，为此对象创建必要的链接，然后resource使用该对象及其链接创建一个新的。
Result
请参阅Postman网站上的api文档
Singe DTO
GET http://localhost:8080/API/categorIEs/6/dto
{
"category": {
"name": "category1"
},
"quantity": 3,
"_links": {
"category": {
"href": "http://localhost:8080/API/categorIEs/6"
},
"self": {
"href": "http://localhost:8080/API/categorIEs/6/dto"
}
}
}
List of DTO
GET http://localhost:8080/API/categorIEs/dto
{
"_embedded": {
"categorIEs": [
{
"category": {
"name": "category1"
},
"quantity": 3,
"_links": {
"category": {
"href": "http://localhost:8080/API/categorIEs/6"
},
"self": {
"href": "http://localhost:8080/API/categorIEs/6/dto"
}
}
},
{
"category": {
"name": "category2"
},
"quantity": 2,
"_links": {
"category": {
"href": "http://localhost:8080/API/categorIEs/7"
},
"self": {
"href": "http://localhost:8080/API/categorIEs/7/dto"
}
}
}
]
},
"_links": {
"self": {
"href": "http://localhost:8080/API/categorIEs/dto"
}
}
}
Paged List of DTO
GET http://localhost:8080/API/categorIEs/dtopaged
{
"_embedded": {
"categorIEs": [
{
"category": {
"name": "category1"
},
"quantity": 3,
"_links": {
"category": {
"href": "http://localhost:8080/API/categorIEs/6"
},
"self": {
"href": "http://localhost:8080/API/categorIEs/6/dto"
}
}
},
{
"category": {
"name": "category2"
},
"quantity": 2,
"_links": {
"category": {
"href": "http://localhost:8080/API/categorIEs/7"
},
"self": {
"href": "http://localhost:8080/API/categorIEs/7/dto"
}
}
}
]
},
"_links": {
"self": {
"href": "http://localhost:8080/API/categorIEs/dtopaged"
}
},
"page": {
"size": 20,
"@R_657_10586@lElements": 2,
"@R_657_10586@lPages": 1,
"number": 0
}
}
Spring Data REST仅自动公开域对象。但是大多数情况下，我们必须处理数据传输对象。那么如何以SDR方式做到这一点呢？
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