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Question

我有一个简单的实体，它映射了一个集合。

@Entity
public class Appointment Identifiable<Integer>   {  

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @JsonIgnore
    private Integer id;

    @Column(name="TRAK_NBR")
    private String trackNumber;

    @OneToMany(fetch =FetchType.EAGER, cascade= CascadeType.ALL)
    @JoinColumn(name="CNSM_APT_VER_WRK_I", nullable = false)
    private Set<Product> products = new HashSet<Product>();
}

@Entity
public class Product implements Identifiable<Integer> {

    @Id
    @Column(name = "CNSM_PRD_VER_WRK_I")
    @GeneratedValue(strategy = GenerationType.AUTO)
    @JsonIgnore
    private Integer id;

    @Column(name = "PRD_MDL_NBR")
    private String model;

    @Column(name = "PRD_SPEC_DSC")
    private String description;
}

在我的应用程序中，当我只包含一个用于约会的 PagingAndSortingRepository 时。我可以使用以下有效负载调用 POST 命令。

{
  "trackNumber" : "XYZ123",
  "products": [
    {"model" : "MODEL",
     "description" : "NAME"
    }]
}

当我为 Product 添加 PagingAndSortingRepository 并尝试相同的 POST 时，我收到以下错误消息。

{
  "cause" : {
    "cause" : {
      "cause" : null,
      "message" : null
    },
    "message" : "(was java.lang.NullPointerException) (through reference chain: com..model.Appointment[\"products\"])"
  },
  "message" : "Could not read JSON: (was java.lang.NullPointerException) (through reference chain: com.model.Appointment[\"products\"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.model.AppointmentVerification[\"products\"])"
}

My GET payload with both Repositories returns this.  This is my desired format.  The link to products should be included

{
  "trackNumber" : "XYZ123", 
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/consumerappointment/appointments/70"
    },
    "products" : {
      "href" : "http://localhost:8080/consumerappointment/appointments/70/products"
  }
}

仅使用 Appointment 存储库，我可以获得以下有效负载并可以发布产品列表。

{
  "trackNumber" : "XYZ123",
  "products" : [ {
    "model" : "MODEL",
    "description" : "NAME",
  } ],
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/consumerappointment/appointments/1"
    }
  }
}

Answer 1

让我们退后一步，确保您了解这里发生的情况：如果检测到存储库，Spring Data REST 会公开一个dedicated set of resources 以便它管理存储库通过 HTTP 处理的聚合。因此，如果您有多个相互关联的实体的存储库，则关系将表示为链接。这就是为什么您在创建 ProductRepository 后看到内联的产品仅包含 AppointmentRepository 和 products 链接的原因。

如果要将两个存储库都公开为资源，则需要将 Product 实例的 URI 传递给 POST 的负载，以创建 Appointment。这意味着，而不是发布这个：

{ "trackNumber" : "XYZ123",
  "products": [
    { "model" : "MODEL",
      "description" : "NAME"
    }
  ]
}

你首先要创建一个Product：

POST /products
{ "model" : "MODEL",
  "description" : "NAME" }

201 Created
Location: …/products/4711

然后将产品的ID交给Appointmentpayload：

{ "trackNumber" : "XYZ123",
  "products": [ "…/products/4711" ]}

如果您不想要任何这些（首先没有为Product 公开资源，请在PersonRepository 上使用@RepositoryRestResource(exported = false)。这仍然会给您留下为repo 创建的bean 实例，但是没有资源被导出，并且为Appointments 暴露的资源返回到内联相关的Products。