使用 spring-boot-2.2.1 删除 HATEOAS link 中的 _embedded

Question

我正在使用 spring-boot-2.2.1 和 spring-HATEOAS。超媒体链接工作正常，但我在 returning 链接时看到 _embedded 属性，请在 github here,

中找到以下代码以供参考和项目

端点：

a) 将 return CollectionModel => localhost:8099/api/v1/capability/list/noembedded

和

b) 将return列出>localhost:8099/api/v1/capability/list/

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>spring-boot-unittest</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-unittest</name>
    <description>Demo project for Spring Boot unit test</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-hateoas</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-mongodb</artifactId>
            <version>4.1.4</version>
        </dependency>

        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-apt</artifactId>
            <version>4.1.4</version>
        </dependency>
        <!-- Embedded  MongoDB for Testing -->
        <dependency>
            <groupId>de.flapdoodle.embed</groupId>
            <artifactId>de.flapdoodle.embed.mongo</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springdoc</groupId>
            <artifactId>springdoc-openapi-ui</artifactId>
            <version>1.2.21</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>com.mysema.maven</groupId>
                <artifactId>apt-maven-plugin</artifactId>
                <version>1.1.3</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>process</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>target/generated-sources/java</outputDirectory>
                            <!--<processor>com.querydsl.mongodb.morphia.MorphiaAnnotationProcessor</processor>-->
                            <processor>org.springframework.data.mongodb.repository.support.MongoAnnotationProcessor</processor>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Controller.Java

@RestController
@RequestMapping(value = "/api/v1/capability")
@RequiredArgsConstructor
@CrossOrigin
public class CapabilityController {

    private final CapabilityService capabilityService;
    private final CapabilityResourceAssembler capabilityResourceAssembler;

    @GetMapping(value = "/list")
    public CollectionModel<EntityModel<Capability>> getAllCapabilities() {
       List<EntityModel<Capability>> capabilities = capabilityService.listCapabilities().stream()
               .map(capability -> new EntityModel<>(capability,
                       linkTo(methodOn(CapabilityController.class).getCapabilityById(capability.getId())).withRel("getThisCapability"),
                       linkTo(methodOn(CapabilityController.class).getAllCapabilities()).withRel("getAllCapabilities")
               )).collect(Collectors.toList());
        return new CollectionModel<>(capabilities);
    }
}

实际回复

{
  "_embedded": {
    "capabilityList": [
      {
        "id": "sample",
        "techStack": "Java",
        "numOfDevelopers": 25,
        "numOfAvailableDevelopers": 10,
        "_links": {
          "getThisCapability": {
            "href": "http://localhost:8099/api/v1/capability/sample"
          },
          "getAllCapabilities": {
            "href": "http://localhost:8099/api/v1/capability/list"
          },
          "deleteThisCapability": {
            "href": "http://localhost:8099/api/v1/capability/sample"
          },
          "createCapability": {
            "href": "localhost:8099/api/v1/capability"
          }
        }
      }
    ]
  }
}

预期响应：

[
  {
    "id": "sample",
    "techStack": "Java",
    "numOfDevelopers": 25,
    "numOfAvailableDevelopers": 10,
    "_links": {
      "getThisCapability": {
        "href": "http://localhost:8099/api/v1/capability/sample"
      },
      "getAllCapabilities": {
        "href": "http://localhost:8099/api/v1/capability/list"
      }
    }
  }
]

我试过了

spring.data.rest.defaultMediaType = application/json

spring.hateoas.use-hal-as-default-json-media-type=false

但运气不好，我仍然能够在响应中看到 _embedded 属性。谁能帮我找出问题所在。

我在使用 spring-boot-1.5.10 之前我可以在没有 _embedded 的情况下正确呈现链接，请参考 here。

我在主 class 中添加以下注释后工作正常，如果我 return List

@EnableHypermediaSupport(type = EnableHypermediaSupport.HypermediaType.HAL)

localhost:9771/api/v1/capability/list

这会产生以下结果：

[
  {
    "capabilityId": "sample",
    "techStack": "Java",
    "numOfDevelopers": 25,
    "numOfAvailableDevelopers": 10,
    "_links": {
      "getThisCapability": {
        "href": "http://localhost:9771/api/v1/capability/sample"
      },
      "getAllCapabilities": {
        "href": "http://localhost:9771/api/v1/capability/list"
      }
    }
  }
]

不幸的是，它在最新版本中不起作用。任何帮助将不胜感激。

Answer 1

如果我理解HAL specification correctly that would be invalid HAL, which is why Spring HATEOAS will not produce this result as long as you return a CollectionModel in your request. Mind that it is possible for the collection to have links as well, which would be next to the _embedded property in a _links property as depicted in this example document.

如果你真的想摆脱 _embedded 属性并生成一个 EntityModel<T> 的列表，那么如果你将代码修改为 [=32 它应该可以工作=]一个List<EntityModel<Capability>>。然后，您将丢失 Spring HATEOAS 生成的 _embedded 和 _links 属性。这是您修改后的代码片段：

@RestController
@RequestMapping(value = "/api/v1/capability")
@RequiredArgsConstructor
@CrossOrigin
public class CapabilityController {

    private final CapabilityService capabilityService;
    private final CapabilityResourceAssembler capabilityResourceAssembler;

    @GetMapping(value = "/list")
    public List<EntityModel<Capability>> getAllCapabilities() {
       List<EntityModel<Capability>> capabilities = capabilityService.listCapabilities().stream()
               .map(capability -> new EntityModel<>(capability,
                       linkTo(methodOn(CapabilityController.class).getCapabilityById(capability.getId())).withRel("getThisCapability"),
                       linkTo(methodOn(CapabilityController.class).getAllCapabilities()).withRel("getAllCapabilities")
               )).collect(Collectors.toList());
        return capabilities;
    }
}

我强烈建议您不要这样做，因为您会失去 Spring HATEOAS 的优势。

此外，我建议使用您的 CapabilityResourceAssembler 并通过使用 capabilityResourceAssembler.toModel(...) 创建 EntityModel<Capability> 个实例，这样您就不必重复您在.map(...) 函数。

Answer 2

使用 Spring Boot 1.5 时，您依赖于 Spring HATEOAS 的限制，这导致 Jackson ObjectMapper 被用作特定于 HAL 的应用范围 ObjectMapper。这种污染意味着 HAL 格式在不应该的情况下应用于响应。

该限制已在 Spring HATEOAS 1.0 中解决，其 HAL 特定 ObjectMapper 不再污染整个应用程序。如果您希望主应用程序 ObjectMapper 应用 HAL 样式的序列化，您可以通过自定义它来选择重新加入：

@Bean
public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder,
                                 HypermediaMappingInformation mappingInformation) {
    ObjectMapper objectMapper = builder.build();
    mappingInformation.configureObjectMapper(objectMapper);
    return objectMapper;
}

虽然我认为上述方法可行，但我会回应 Daniel 在他们的回答中提出的关于响应格式和 HAL 规范合规性的问题。

Answer 3

我建议使用注释为@JsonValue 的类型集合字段扩展 CollectionModel，然后在您的汇编器中将 toCollectionModel 覆盖为 return 自定义 CollectionModel

public class CustomCollectionModel<T> extends CollectionModel<CollectionModel<T>>  {
@JsonValue
private Collection<T> content;

protected CustomCollectionModel() {
    this(new ArrayList<>());
}

public CustomCollectionModel(Iterable<T> content, Link... links) {
    this(content, Arrays.asList(links));
}


public CustomCollectionModel(Iterable<T> content, Iterable<Link> links) {

    Assert.notNull(content, "Content must not be null!");

    this.content = new ArrayList<>();

    for (T element : content) {
        this.content.add(element);
    }

    this.add(links);
}}

然后在你的汇编程序中

  @Override
public CustomCollectionModel toCollectionModel(Iterable<? extends T> entities) {
    List<EntityModel<T>> resourceList = new ArrayList<>();

    for (T entity : entities) {
        resourceList.add(toModel(entity));
    }
    return new CustomCollectionModel(resourceList);
}

Answer 4

这对您来说仍然是个问题吗？通过将 false 作为参数传递给 RepositoryRestConfiguration class.

中的 useHalAsDefaultJsonMediaType 方法，我能够删除 _embedded 属性

使用 spring-boot-2.2.1 删除 HATEOAS link 中的 _embedded

Remove _embedded in HATEOAS link using spring-boot-2.2.1

java

spring

spring-boot

spring-data-mongodb

spring-hateoas