没有数据休息的HATEOAS + Pagination in Spring的简单实现吗？

Question

几天来我一直在寻找如何实现包含 HATEOAS 链接的 Spring REST API + 使用 Spring boot 和 JPA 进行分页（无 spring 数据休息），就像这个随机示例：

{
    "_links": {
        "first": {
            "href": "http://localhost:8080/api/albums-list?page=0&size=2&sort=title,desc"
        },
        "prev": {
            "href": "http://localhost:8080/api/albums-list?page=0&size=2&sort=title,desc"
        },
        "self": {
            "href": "http://localhost:8080/api/albums-list?page=1&size=2&sort=title,desc"
        },
        "next": {
            "href": "http://localhost:8080/api/albums-list?page=2&size=2&sort=title,desc"
        },
        "last": {
            "href": "http://localhost:8080/api/albums-list?page=4&size=2&sort=title,desc"
        }
    },
    "page": {
        "size": 2,
        "totalElements": 10,
        "totalPages": 5,
        "number": 1
    },
    "_embedded": {
        "albums": [
            {
                "id": 7,
                "title": "Top Hits Vol 7",
                "description": "Top hits vol 7. description",
                "releaseDate": "10-03-1987",
                "actors": [
                    {
                        "id": 4,
                        "firstName": "Janice",
                        "lastName": "Preston",
                        "_links": {
                            "self": {
                                "href": "http://localhost:8080/api/actors/4"
                            }
                        }
                    }
                ],
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/api/actors/7"
                    }
                }
            },
            {
                "id": 6,
                "title": "Top Hits Vol 6",
                "description": "Top hits vol 6. description",
                "releaseDate": "10-03-1986",
                "actors": [
                    {
                        "id": 3,
                        "firstName": "Laverne",
                        "lastName": "Mann",
                        "_links": {
                            "self": {
                                "href": "http://localhost:8080/api/actors/3"
                            }
                        }
                    }
                ],
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/api/actors/6"
                    }
                }
            }
        ]
    }
}

然而，到目前为止我找到的解决方案非常复杂，或者样板文件的数量非常可笑 这个解决方案例如： https://howtodoinjava.com/spring5/hateoas/pagination-links/ 页面上的教程并没有完全展示它，但它需要您创建实体、实体模型和一个充满样板的长 RepresentationModelAssemblerSupport

我也试过这个： https://spring.io/guides/tutorials/rest/ 但是嵌套类（我有一对多/多对一的关系）没有获得 HATEOAS 的链接：

{
    "id": 3,
    "nome": "Amazonas",
    "uf": "AM",
    "cidades": [
        {
        //no HATEOAS in here
            "id": 10003,
            "nome": null,
            "instituicoes": [],
            "uf": "AM"
        },
        {
            "id": 219,
            "nome": "Alvarães",
            "instituicoes": [],
            "uf": "AM"
        }
    ],
    "_links": {
        "self": {
            "href": "http://localhost:8080/api/v1/estados/estadoes/3"
        },
        "estadoes": {
            "href": "http://localhost:8080/api/v1/estados/estadoes"
        }
    }
}

我的意思是，难道没有更简单的解决方案吗？幸运的是，分页 PagingAndSortingRepository 很有用，但同时具有分页 + HATEOAS，真是一场噩梦。

Answer 1

A

RepresentationModelAssembler

是必需的。如果您不需要其他字段，则不需要模型类

extends EntityModel<T>

。

我的示例实体类是

Inventory

.

RepresentationModelAssembler。您可以在此处添加更多链接。

@Component
public class InventoryModelAssembler implements RepresentationModelAssembler<Inventory, EntityModel<Inventory>> {

    @Override
    public EntityModel<Inventory> toModel(Inventory inventory) {

        return EntityModel.of(inventory,
                linkTo(methodOn(InventoryController.class).get(inventory.getId()))
                        .withSelfRel());
    }
}

控制器

@RestController
@RequestMapping("/inventories")
@RequiredArgsConstructor
public class InventoryController {

    private final InventoryRepository inventoryRepository;

    private final PagedResourcesAssembler pagedResourcesAssembler;

    private final InventoryModelAssembler inventoryModelAssembler;

    @GetMapping
    public ResponseEntity get(Pageable pageable) {

        Page<Inventory> inventories = inventoryRepository.findAll(pageable);

        return ResponseEntity
                .ok()
                .contentType(MediaTypes.HAL_JSON)
                .body(pagedResourcesAssembler.toModel(inventories, inventoryModelAssembler));
    }
}

HAL JSON 响应。可以在我的 HTML 文档 中找到完整的长回复。下载并使用浏览器打开。

{
  "_embedded" : {
    "inventories" : [ {
      "carrier" : "SG",
      "fltNum" : "001",
      "serviceType" : "PAX",
      "fltDate" : "2020-01-20",
      "fltDow" : 1,
      "createdDate" : "2020-06-11T13:21:44.992Z",
      "lastModifiedDate" : "2020-06-11T13:21:44.992Z",
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/inventories/5ee22fe8853b0f45ae5fca27"
        }
      }
    }]
  },
  "_links" : {
    "first" : {
      "href" : "http://localhost:8080/inventories?carrier=SG&fltNum=001&page=0&size=10&sort=fltNum,asc&sort=fltDate,desc"
    },
    "self" : {
      "href" : "http://localhost:8080/inventories?carrier=SG&fltNum=001&page=0&size=10&sort=fltNum,asc&sort=fltDate,desc"
    },
    "next" : {
      "href" : "http://localhost:8080/inventories?carrier=SG&fltNum=001&page=1&size=10&sort=fltNum,asc&sort=fltDate,desc"
    },
    "last" : {
      "href" : "http://localhost:8080/inventories?carrier=SG&fltNum=001&page=1&size=10&sort=fltNum,asc&sort=fltDate,desc"
    }
  },
  "page" : {
    "size" : 10,
    "totalElements" : 20,
    "totalPages" : 2,
    "number" : 0
  }
}

完整代码在Github中共享。如果我的项目对这个答案有帮助，请考虑在 Github 中给它一个星号。

Answer 2

在这个例子中用代码有一个很好的解释 分页（使用 Hateoas），使用 Spring Boot 和 JPA 进行过滤和排序 展示了多种方法。这完全涵盖了实现分页的方法，包括没有 spring data rest 的排序和过滤。