Spring-boot + REST + HATEOAS + HAL

Question

我按照 spring.io Pivotal 教程获得了带有 MySQL 数据库的 REST API，并且进展顺利。但是，我发现了一个我无法配置或变通的行为。

当我使用内置功能从 PagingAndSortingRepository 检索资源时，生成的 REST 自动分页并封装有有用的 HAL 链接（_links、self、search、链接资源等）。我想用那个。

当我实现我的控制器来自定义 PostMapping 行为并引入完整性检查、验证等时，GetMapping 停止工作。所以我重新实现了一个利用我的服务层的 GetMapping。

不幸的是，这样做破坏了之前提供的 HATEOAS。

我想要的是能够自定义 PostMapping，但保留与默认值完全相同的 GetMapping。如果可能的话，我很想避免自己编写它，因为我知道框架可以提供它。

有什么办法吗？

控制器：

@RestController
public class PartyMemberController {

    @Autowired
    PartyMemberService partyMemberService;

    @RequestMapping(method = RequestMethod.GET, value = "/partyMembers")
    public ResponseEntity<Iterable<PartyMember>> getAllPartyMembers() {
        Iterable<PartyMember> partyMemberList = partyMemberService.getAll();
        return new ResponseEntity<>(partyMemberList, HttpStatus.OK);
    }

    @RequestMapping(method = RequestMethod.POST, value = "/partyMembers")
    public ResponseEntity<PartyMember> addEmployee(@Valid @RequestBody PartyMember partyMember) {
        if (partyMemberService.exists(partyMember)) {
            return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
        }

        partyMember = partyMemberService.save(partyMember);
        return new ResponseEntity<PartyMember>(partyMember, HttpStatus.CREATED);
    }
}

结果 JSON

    [
      {
        "id": 2,
        "ward": {
          "id": 1,
          "name": "Mercier",
          "wardNumber": 42,
          "numberOfMembers": 3
        },
        "firstName": "Cindy",
        "lastName": "Tremblay",
        "partyMemberId": "12-1234-09876",
        "primaryPhone": "514-555-2323",
        "postalAddress": "1155 Robert-Bourassa, Montreal, Quebec, Canada, H3B3A7",
        "emailAddress": null,
        "secondaryPhone": null,
        "bestTimeToContact": null,
        "bestWayToContact": null,
        "membershipExpiry": null,
        "dateOfBirth": null,
        "donationEntries": [],
        "note": null
      },
      {
        "id": 3,
        "ward": {
          "id": 1,
          "name": "Mercier",
          "wardNumber": 42,
          "numberOfMembers": 3
        },
        "firstName": "Robert",
        "lastName": "Paulson",
        "partyMemberId": "12-1234-54321",
        "primaryPhone": "514-555-1212",
        "postalAddress": "440 Rue Saint-Pierre, App 5, Montreal, Quebec, Canada, H2Y2M5",
        "emailAddress": "rpaulson@papermillsoapcompany.com",
        "secondaryPhone": null,
        "bestTimeToContact": null,
        "bestWayToContact": null,
        "membershipExpiry": null,
        "dateOfBirth": null,
        "donationEntries": [],
        "note": null
      },
      {
        "id": 4,
        "ward": {
          "id": 1,
          "name": "Mercier",
          "wardNumber": 42,
          "numberOfMembers": 3
        },
        "firstName": "Richard",
        "lastName": "Schnobb",
        "partyMemberId": "12-4321-09876",
        "primaryPhone": "514-555-2323",
        "postalAddress": "440 Rue Saint-Pierre, App 5, Montreal, Quebec, Canada, H2Y2M5",
        "emailAddress": null,
        "secondaryPhone": null,
        "bestTimeToContact": null,
        "bestWayToContact": null,
        "membershipExpiry": null,
        "dateOfBirth": null,
        "donationEntries": [],
        "note": null
      }
    ]

默认 JSON（注意 _embedded、_links 等）。这就是我想要的结果。

{
  "_embedded" : {
    "partyMembers" : [ {
      "firstName" : "Cindy",
      "lastName" : "Tremblay",
      "partyMemberId" : "12-1234-09876",
      "primaryPhone" : "514-555-2323",
      "postalAddress" : "1155 Robert-Bourassa, Montreal, Quebec, Canada, H3B3A7",
      "emailAddress" : null,
      "secondaryPhone" : null,
      "bestTimeToContact" : null,
      "bestWayToContact" : null,
      "membershipExpiry" : null,
      "dateOfBirth" : null,
      "donationEntries" : [ ],
      "note" : null,
      "_links" : {
        "self" : {
          "href" : "http://127.0.0.1:8080/partyMembers/2"
        },
        "partyMember" : {
          "href" : "http://127.0.0.1:8080/partyMembers/2"
        },
        "ward" : {
          "href" : "http://127.0.0.1:8080/partyMembers/2/ward"
        }
      }
    }, {
      "firstName" : "Robert",
      "lastName" : "Paulson",
      "partyMemberId" : "12-1234-54321",
      "primaryPhone" : "514-555-1212",
      "postalAddress" : "440 Rue Saint-Pierre, App 5, Montreal, Quebec, Canada, H2Y2M5",
      "emailAddress" : "rpaulson@papermillsoapcompany.com",
      "secondaryPhone" : null,
      "bestTimeToContact" : null,
      "bestWayToContact" : null,
      "membershipExpiry" : null,
      "dateOfBirth" : null,
      "donationEntries" : [ ],
      "note" : null,
      "_links" : {
        "self" : {
          "href" : "http://127.0.0.1:8080/partyMembers/3"
        },
        "partyMember" : {
          "href" : "http://127.0.0.1:8080/partyMembers/3"
        },
        "ward" : {
          "href" : "http://127.0.0.1:8080/partyMembers/3/ward"
        }
      }
    }, {
      "firstName" : "Richard",
      "lastName" : "Schnobb",
      "partyMemberId" : "12-4321-09876",
      "primaryPhone" : "514-555-2323",
      "postalAddress" : "440 Rue Saint-Pierre, App 5, Montreal, Quebec, Canada, H2Y2M5",
      "emailAddress" : null,
      "secondaryPhone" : null,
      "bestTimeToContact" : null,
      "bestWayToContact" : null,
      "membershipExpiry" : null,
      "dateOfBirth" : null,
      "donationEntries" : [ ],
      "note" : null,
      "_links" : {
        "self" : {
          "href" : "http://127.0.0.1:8080/partyMembers/4"
        },
        "partyMember" : {
          "href" : "http://127.0.0.1:8080/partyMembers/4"
        },
        "ward" : {
          "href" : "http://127.0.0.1:8080/partyMembers/4/ward"
        }
      }
    } ]
  },
  "_links" : {
    "self" : {
      "href" : "http://127.0.0.1:8080/partyMembers{?page,size,sort}",
      "templated" : true
    },
    "profile" : {
      "href" : "http://127.0.0.1:8080/profile/partyMembers"
    },
    "search" : {
      "href" : "http://127.0.0.1:8080/partyMembers/search"
    }
  },
  "page" : {
    "size" : 20,
    "totalElements" : 3,
    "totalPages" : 1,
    "number" : 0
  }
}

Answer 1

您对 ResponseEntity 的控制很糟糕，所以它不再为您自动构建。这意味着您必须使用 LinkBuilder 或 ControllerLinkBuilder 来构建与您自己的 ResponseEntity 关联的链接。

此处的文档和示例：https://docs.spring.io/spring-hateoas/docs/current/reference/html/#fundamentals.obtaining-links.entity-links

快速示例：

@Getter 
public class PersonResource extends ResourceSupport {
    private final Person person;
    public PersonResource(final Person person) {
        this.person = person;
        final long id = person.getId();
        add(linkTo(PersonController.class).withRel("people"));
        add(linkTo(methodOn(GymMembershipController.class).all(id)).withRel("memberships"));
        add(linkTo(methodOn(PersonController.class).get(id)).withSelfRel());
    }
}

来自这个最优秀的图：https://dzone.com/articles/applying-hateoas-to-a-rest-api-with-spring-boot

Answer 2

要让 Spring 为您完成大部分工作，您应该使用注释 @RepositoryRestController。更多解释在 docs:

Sometimes, you may want to write a custom handler for a specific resource. To take advantage of Spring Data REST’s settings, message converters, exception handling, and more, use the @RepositoryRestController annotation instead of a standard Spring MVC @Controller or @RestController. Controllers annotated with @RepositoryRestController are served from the API base path defined in RepositoryRestConfiguration.setBasePath, which is used by all other RESTful endpoints (for example, /api).

为了简化 HATEOAS 资源的生成（使用您提到的 _links），您可以利用 ResourceAssemblerSupport。

As the mapping from an entity to a resource type will have to be used in multiple places it makes sense to create a dedicated class responsible for doing so. The conversion will of course contain very custom steps but also a few boilerplate ones. (...) Spring Hateoas now provides a ResourceAssemblerSupport base class that helps reducing the amount of code needed to be written

Answer 3

您控制器上的 return 类型不是 Spring HATEOAS ResourceSupport 类型，因此永远不会调用它的 HAL 序列化程序。

您应该 return Resource<PartyMember>（对于单个项目）或 Resources<Resource<PartyMember>>（对于列表）。将您的控制器构造为 return 这些。

进行这些更改，然后可重用的概念 ResourceAssembler<PartyMember, Resource<PartyMember>> 将非常有意义，因为它可以将服务层中找到的 PartyMember 个对象转换为 Resource<PartyMember> 个用于呈现超媒体。

要了解基于 REST 的服务的这种演变，请查看本教程（我在几个月前重写以正确显示 Spring HATEAOS 的用法）=> https://spring.io/guides/tutorials/rest/

Spring-boot + REST + HATEOAS + HAL

Spring-boot + REST + HATEOAS + HAL

java

spring-boot

spring-restcontroller

spring-hateoas