json - 在 Go 中解析 JSON

Question

我是 Go 的新手，我正在构建一个 Web API，它在我的 Android 应用程序中使用来自 RDW 的数据。然而，我在 Go 中解析 JSON 时遇到了问题，而在 Java 中我可以轻松地使用类似 jsonObject.getString("AreaId") 的东西。我似乎无法在 Go 中执行此操作。

我正在尝试解析以下 JSON 以将其保存在 MySQL 数据库中:

{
  'd': {
    'results': [
      {
        '__metadata': {
          'id': 'https://api.datamarket.azure.com/Data.ashx/opendata.rdw/StatischParkeren.Open.Data/v1/AREAGEOMETRY(1)',
          'uri': 'https://api.datamarket.azure.com/Data.ashx/opendata.rdw/StatischParkeren.Open.Data/v1/AREAGEOMETRY(1)',
          'type': 'opendata.rdw.StatischParkeren.Open.Data.AREAGEOMETRY'
        },
        'AREAGEOMETRY_ID': 1,
        'AreaManagerId': '34',
        'AreaId': 'ALMBUITEN',
        'EndDateArea': null,
        'StartDateArea': '/Date(1330560000000)/',
        'AreaGeometryTxt': 'POLYGON ((5.2736760005354881 52.391216600313783, 5.2752534225583076 52.392331821843982, 5.2771425843238831 52.391448376700282, 5.2795117920336709 52.392518069183787, 5.2794937640428543 52.392529543489218, 5.2795250192284584 52.392524041235447, 5.2795117920336709 52.392518069183787, 5.27959094196558 52.392467692494392, 5.28429589420557 52.394528595730662, 5.2830820381641388 52.3958012573421, 5.2826158106327057 52.396464187651873, 5.28216527402401 52.396755328401923, 5.2811877280473709 52.396325327456, 5.27938649058342 52.395481485873461, 5.2793451324105263 52.395514352247119, 5.2788525596261024 52.395813956856728, 5.278492659330368 52.39611235447228, 5.2776647135615349 52.396820867434144, 5.2777034044265747 52.396853528916836, 5.2768759876489639 52.397581102326512, 5.274177111685276 52.396415254101157, 5.2741994857788086 52.396424867212772, 5.2686141580343246 52.394008679315448, 5.26860549300909 52.394005045294762, 5.2691666409373283 52.39350445382297, 5.2705547362565994 52.392721636220813, 5.2723518460904533 52.392156438032842, 5.2723518460989 52.39215643890202, 5.272359311580658 52.392154090106487, 5.2723518460904533 52.392156438032842, 5.2723498195409775 52.391947904601693, 5.273051455616951 52.391403153538704, 5.2736760005354881 52.391216600313783))',
        'AreaGeometryGml': '<Polygon xmlns="http://www.opengis.net/gml"><exterior><LinearRing><posList>5.2736760005354881 52.391216600313783 5.2752534225583076 52.392331821843982 5.2771425843238831 52.391448376700282 5.2795117920336709 52.392518069183787 5.2794937640428543 52.392529543489218 5.2795250192284584 52.392524041235447 5.2795117920336709 52.392518069183787 5.27959094196558 52.392467692494392 5.28429589420557 52.394528595730662 5.2830820381641388 52.3958012573421 5.2826158106327057 52.396464187651873 5.28216527402401 52.396755328401923 5.2811877280473709 52.396325327456 5.27938649058342 52.395481485873461 5.2793451324105263 52.395514352247119 5.2788525596261024 52.395813956856728 5.278492659330368 52.39611235447228 5.2776647135615349 52.396820867434144 5.2777034044265747 52.396853528916836 5.2768759876489639 52.397581102326512 5.274177111685276 52.396415254101157 5.2741994857788086 52.396424867212772 5.2686141580343246 52.394008679315448 5.26860549300909 52.394005045294762 5.2691666409373283 52.39350445382297 5.2705547362565994 52.392721636220813 5.2723518460904533 52.392156438032842 5.2723518460989 52.39215643890202 5.272359311580658 52.392154090106487 5.2723518460904533 52.392156438032842 5.2723498195409775 52.391947904601693 5.273051455616951 52.391403153538704 5.2736760005354881 52.391216600313783</posList></LinearRing></exterior></Polygon>'
      },
      {
        '__metadata': {
          'id': 'https://api.datamarket.azure.com/Data.ashx/opendata.rdw/StatischParkeren.Open.Data/v1/AREAGEOMETRY(2)',
          'uri': 'https://api.datamarket.azure.com/Data.ashx/opendata.rdw/StatischParkeren.Open.Data/v1/AREAGEOMETRY(2)',
          'type': 'opendata.rdw.StatischParkeren.Open.Data.AREAGEOMETRY'
        },
        'AREAGEOMETRY_ID': 2,
        'AreaManagerId': '34',
        'AreaId': 'ALMTEGELZ',
        'EndDateArea': null,
        'StartDateArea': '/Date(1330560000000)/',
        'AreaGeometryTxt': 'POLYGON ((5.216308925 52.370733155, 5.216800447 52.370804276, 5.216837124 52.370755791, 5.217178542 52.370807152, 5.217373999 52.370322534, 5.217353484 52.370319431, 5.217371539 52.370274734, 5.216664547 52.370167441, 5.216571837 52.370396589, 5.216451509 52.370380301, 5.216308925 52.370733155))',
        'AreaGeometryGml': '<Polygon xmlns="http://www.opengis.net/gml"><exterior><LinearRing><posList>5.216308925 52.370733155 5.216800447 52.370804276 5.216837124 52.370755791 5.217178542 52.370807152 5.217373999 52.370322534 5.217353484 52.370319431 5.217371539 52.370274734 5.216664547 52.370167441 5.216571837 52.370396589 5.216451509 52.370380301 5.216308925 52.370733155</posList></LinearRing></exterior></Polygon>'
      },
 ],
    '__next': 'https://api.datamarket.azure.com/Data.ashx/opendata.rdw/StatischParkeren.Open.Data/v1/AREAGEOMETRY?$skiptoken=100'
  }
}

这是我在 Go 中的代码:

type Data struct {
    Next string
    Results Result
}

type Result struct {
    Results []AreaGeometry
}

type AreaGeometry struct {
    AREAGEOMETRY_ID int32
    AreaManagerId int64
    AreaId string
    EndDateArea string
    StartDateArea string
    AreaGeometryTxt string
}

// Synchronizes the AreaGeometry in our MySQL database with the AreaGeometry in the database from the RDW
func retrieveData() {
    resp, err := http.Get("https://api.datamarket.azure.com/opendata.rdw/StatischParkeren.Open.Data/v1/AREAGEOMETRY?$format=json")
    if err != nil {
        panic(err.Error()) // TODO: proper error handling
    }
    body, err := ioutil.ReadAll(resp.Body)
    var d Data
    json.Unmarshal(body, &d)
    fmt.Println("Next: " + d.Next)
}

但是，d.Next 在解码后返回一个空字符串。我究竟做错了什么？ Go 的处理方式是什么？

Answer 1

您需要使用 JSON 注释(在文档中称为结构“标签”)让它知道字段在 JSON 中的名称:

type Data struct {
    Next string `json:"__next"` //Field appears in JSON as key "__next".
    Results Result `json:"results"`
}

我相信 Go 会自动处理 results 与 Results，但如果你要发回数据并希望它是小写的，你仍然需要注释。

您的 Results Result 不正确 - Results 不是 Result 类型的对象，它是 AreaGeometry 数组，因此它应该如下所示:

type Data struct {
    Next string  `json:"__next"` //Field appears in JSON as key "__next".
    Results []AreaGeometry
}

此外，您还需要对 JSON 中的 D 对象进行包装:

type D struct {
    D Data `json:"d"`
}


func main() {
    body := jsonString //too long to put here, but in the playground. 
    var d D
    err := json.Unmarshal([]byte(body), &d)
    if (err != nil) {
       fmt.Println(err)
    }
    fmt.Println("Next: " + d.D.Next)

}

http://play.golang.org/p/yK-zNxEMvy