Question

我刚刚开始学习graphql，我创建了一个查询，该查询返回了前10个已关闭问题的列表以及一些属性。令我惊讶的是，我在JSON中获得的响应对象有时为空，有时又为非空。回答是随机的。我也曾与邮递员进行过测试。由于我正在使用jackson将json响应映射到Java类并执行一些操作，因此在处理空对象时会引发异常。

1）基本上，我想要一个非空对象的已关闭问题。查询中有什么问题吗？如果是，有人可以告诉正确的查询吗？

2）另外，我想知道返回空节点对象背后的逻辑

使用查询


{
  search(first: 20, type: ISSUE, query: "created:<2019-09-21 state:closed") {
    issueCount
    edges {
      node {
        ... on Issue {
          createdAt
          closedAt
          title
          url
          repository {
            name
          }
        }
      }
    }
  }
}

响应1

{
    "data": {
        "search": {
            "issueCount": 92339271,
            "edges": [
                {
                    "node": {
                        "createdAt": "2019-09-20T23:59:57Z",
                        "closedAt": "2019-09-21T19:59:32Z",
                        "title": "MJPEG stream won't open",
                        "url": "https://github.com/mpv-player/mpv/issues/6964",
                        "repository": {
                            "name": "mpv"
                        }
                    }
                },
                {
                    "node": {
                        "createdAt": "2019-09-20T23:59:50Z",
                        "closedAt": "2019-09-21T01:19:39Z",
                        "title": "Upgrade from v0.5.0 to v0.6.0 with attached volume failed",
                        "url": "https://github.com/longhorn/longhorn/issues/745",
                        "repository": {
                            "name": "longhorn"
                        }
                    }
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {
                        "createdAt": "2019-09-20T23:58:52Z",
                        "closedAt": "2019-09-21T01:55:15Z",
                        "title": "bad linkage",
                        "url": "https://github.com/signalapp/Signal-Desktop/issues/3608",
                        "repository": {
                            "name": "Signal-Desktop"
                        }
                    }
                },
                {
                    "node": {}
                },
                {
                    "node": {
                        "createdAt": "2019-09-20T23:58:36Z",
                        "closedAt": "2019-09-21T00:57:54Z",
                        "title": "Breaks Some Links on Firefox for Mac",
                        "url": "https://github.com/duckduckgo/duckduckgo-privacy-extension/issues/416",
                        "repository": {
                            "name": "duckduckgo-privacy-extension"
                        }
                    }
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {
                        "createdAt": "2019-09-20T23:56:11Z",
                        "closedAt": "2019-09-23T18:43:30Z",
                        "title": "ci: upload coverage reports from GitHub Actions",
                        "url": "https://github.com/hyperledger/aries-framework-go/issues/314",
                        "repository": {
                            "name": "aries-framework-go"
                        }
                    }
                },
                {
                    "node": {}
                },
                {
                    "node": {
                        "createdAt": "2019-09-20T23:56:07Z",
                        "closedAt": "2019-09-21T02:53:35Z",
                        "title": "0xxx.ws",
                        "url": "https://github.com/NanoMeow/QuickReports/issues/1885",
                        "repository": {
                            "name": "QuickReports"
                        }
                    }
                }
            ]
        }
    }
}

响应2

{
    "data": {
        "search": {
            "issueCount": 92339271,
            "edges": [
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {
                        "createdAt": "2019-09-20T23:58:36Z",
                        "closedAt": "2019-09-21T00:57:54Z",
                        "title": "Breaks Some Links on Firefox for Mac",
                        "url": "https://github.com/duckduckgo/duckduckgo-privacy-extension/issues/416",
                        "repository": {
                            "name": "duckduckgo-privacy-extension"
                        }
                    }
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                },
                {
                    "node": {}
                }
            ]
        }
    }
}

Answer 1

node字段的类型为SearchResultItem，即interface。接口是一种抽象类型，代表一种或多种实现该接口的对象类型。换句话说，搜索结果中任何特定node字段的类型都可以是以下几种类型之一-Issue，PullRequest，Repository等。

查询抽象类型（接口或联合）时，必须使用inline fragments来指定要获取的每种可能类型的字段。因此，对于搜索，我们写：

... on Issue {
  # some fields here
}
... on PullRequest {
  # some other fields here
}
... on Repository {
  # yet some other fields here
}

，依此类推。内联片段仅告诉GraphQL对于给定类型返回哪些字段。 它们不会过滤搜索的实际结果。您不必为每种可能的类型都提供内联片段，但是如果您不提供其中的一种，并且结果会返回该类型，它将作为一个空对象返回（再次，因为您没有告诉GraphQL您想要该特定类型的字段）。

GraphQL不提供任何内置方法来过滤，排序或对返回的数据进行其他处理。必要时，由单个服务来实现该功能。在这种特定情况下，即使type字段上有一个search自变量，将自变量的值设置为ISSUE仍会实际上返回两种不同的类型-Issue和PullRequest。因此，如果要避免为某些搜索结果接收到空对象，则PullRequest仍需要另一个内联片段。

从graphql响应返回空的“节点”对象

1 个答案: