Jackson模块处理Spring Data REST中的抽象聚合根及其子类

Question

public interface CriterionRepository extends JpaRepository<Criterion, Long> {
}

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class Criterion extends AbstractEntity {}

@Entity
public class NameCriterion extends Criterion {
    private final String name;
}

Spring Data REST将存储库导出为REST资源，您可以在http://localhost:8080/api/criterial/上访问它

导出的资源如下所示：

{
    "_embedded": {
        "nameCriteria": [{
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/api/nameCriterion/1"
                    },
                    "nameCriterion": {
                        "href": "http://localhost:8080/api/nameCriterion/1"
                    }
                }
            }
        ]
    },
    "_links": {
        "self": {
            "href": "http://localhost:8080/api/criteria"
        },
        "profile": {
            "href": "http://localhost:8080/api/profile/criteria"
        }
    },
    "page": {
        "size": 20,
        "totalElements": 1,
        "totalPages": 1,
        "number": 0
    }
}

当我尝试跟踪self链接时，没有http：//localhost:8080/api/namecriterion/1的映射

{
    "_links": {
        "self": {
            "href": "http://localhost:8080/api/nameCriterion/1"
        },
        "nameCriterion": {
            "href": "http://localhost:8080/api/nameCriterion/1"
        }
    }
}

换句话说，我应该创建什么Jackson模块？

Answer 1

不需要创建Jackson模块。要为继承的实体使用单个表，我们可以使用@RestResource注释将它们标记为相同的资源：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@Table(name = "criteria")
public abstract class Criterion extends AbstractEntity {
}

@RestResource(rel = "criteria", path = "criteria")
@Entity
public class NameCriterion extends Criterion {

    private String name;
}

@RestResource(rel = "criteria", path = "criteria")
@Entity
public class TitleCriterion extends Criterion {

    private String title;
}

@RepositoryRestResource(path = "criteria", collectionResourceRel = "criteria", itemResourceRel = "criterion")
public interface CriterionRepository extends JpaRepository<Criterion, Long> {
}

因此可以在一个输出中获得所有资源（NameCriterion和TitleCriterion）：

json prettyprint-override">GET http://localhost:8080/api/criteria

{
  "_embedded": {
    "criteria": [
      {
        "name": "name1",
        "_links": {
          "self": {
            "href": "http://localhost:8080/api/criteria/1"
          },
          "nameCriterion": {
            "href": "http://localhost:8080/api/criteria/1"
          }
        }
      },
      {
        "title": "title1",
        "_links": {
          "self": {
            "href": "http://localhost:8080/api/criteria/2"
          },
          "titleCriterion": {
            "href": "http://localhost:8080/api/criteria/2"
          }
        }
      }
    ]
  }
}

GET http://localhost:8080/api/criteria/1
{
  "name": "name1",
  "_links": {
    "self": {
      "href": "http://localhost:8080/api/criteria/1"
    },
    "nameCriterion": {
      "href": "http://localhost:8080/api/criteria/1"
    }
  }
}

GET http://localhost:8080/api/criteria/2
{
  "title": "title1",
  "_links": {
    "self": {
      "href": "http://localhost:8080/api/criteria/2"
    },
    "titleCriterion": {
      "href": "http://localhost:8080/api/criteria/2"
    }
  }
}

工作实例。