Question

我一直在寻找有关如何实现包含HATEOAS链接+使用Spring Boot和JPA分页的Spring REST API（无Spring数据静态）的几天，

{
    "_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"
                    }
                }
            }
        ]
    }
}

但是，到目前为止，我发现的解决方案非常复杂，或者样板数量可笑例如此解决方案： https://howtodoinjava.com/spring5/hateoas/pagination-links/ 该页面上的教程并未完整介绍它，但需要您创建实体，该实体的模型以及一个很长的样板样的长RepresentationModelAssemblerSupport

我也尝试过这样做： https://spring.io/guides/tutorials/rest/ 但是，嵌套类（我的关系是一对多/很多一对一的关系）无法获得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，没有更简单的解决方案吗？幸运的是，对于分页，PagingAndSortingRepository很有用，但是同时拥有分页和HATEOAS，真是一场噩梦。

Answer 1

需要RepresentationModelAssembler。如果您不需要其他字段，则不需要模型类extends EntityModel<T>。

我的示例实体类为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。在我的HTML doc中可以找到完整的答复。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。如果我的项目除此答案以外还有帮助，请考虑在Github中给它加星号。

春季是否可以在没有数据休息的情况下简单实现HATEOAS +分页？

1 个答案: