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社区首页 >问答首页 >API调用问题

问API调用问题
EN

Stack Overflow用户
提问于 2018-09-26 13:51:43
回答 2查看 72关注 0票数 1

我正在尝试使用以下内容将一些数据点发送到web api。(不确定要不要共享密钥，所以我留了一部分)。

代码语言：javascript
复制
library(jsonlite)
library(httr)

url = "https://api.marketcycles.online/api/CycleScanner"
t <- 1:101
val <- 2*sin(2*pi*t/25) + 5*cos(2*pi*t/50)
val[1:3]
body.list <- list(datapoints = val)
query.list <- list(api_Key = "wtt****")
res <- POST(url = url, query = query.list, body = body.list,
            encode = "json")
a <- content(res, as = "text")
b <- fromJSON(a)
b[[2]]

这会导致错误"Object reference not set to an object instance“

下面的curl命令可以工作(我已经编辑掉了大部分数据点)

代码语言：javascript
复制
curl -X POST --header 'Content-Type: application/json' \
    --header 'Accept: application/json' \
    -d '[5.458,5.8064,6.018,....5,5.458]' \
    'https://api.marketcycles.online/api/CycleScanner?api_Key=wtt****'

对POST命令的工作有什么建议吗？

谢谢你的回答hrbrmstr。非常感谢。我尝试了以下几种方法

代码语言：javascript
复制
httr::POST(
  url = "https://api.marketcycles.online/api/CycleScanner",
  httr::content_type_json(),
  httr::accept_json(),
  encode = "json", 
  body = jsonlite::toJSON(val),
  query = list(
    amplitudeMulti = "1.0",
    bartelsLimit = "49",
    minCycleLength = "5",
    maxCycleLength = "300",
    sortByStrength = "true",
    includeSpectrum = "false",
    humanReadableText = "false",
    api_Key = "wtt****")
)

使用和不使用带有content_type_jason()的行，并在这两种情况下都收到以下错误

代码语言：javascript
复制
b[[1]]
[1] "The request contains an entity body but no Content-Type header. The
inferred media type 'application/octet-stream' is not supported for this
resource."
b[[2]]
[1] "No MediaTypeFormatter is available to read an object of type
'Double[]' from content with media type 'application/octet-stream'."
b[[3]]
[1] "System.Net.Http.UnsupportedMediaTypeException"

据我所知，当主体是一个列表时，encode()提供列表元素的格式。当它不是的时候，我不清楚该怎么做。我查看了httr源代码，发现有一个未记录的函数body_config，但不确定是否在POST命令中使用此函数。有什么建议可以解决这个问题吗？

r
post
httr
EN

回答 2

Stack Overflow用户

发布于 2018-09-26 19:24:09

我没有API键(你没有分享你的是100%正确的)，但是他们的Swagger API Docs有点像他们期望的输入。

我在他们提供的在线Swagger测试器中使用了一个带有该端点的假API键(知道它会失败，但仍然显示curl行)，并填充了默认值，以全面了解端点所期望的内容，它返回了以下内容(格式由我设置，返回一行)：

代码语言：javascript
复制
curl 
  -X POST 
  --header 'Content-Type: application/json' 
  --header 'Accept: application/json' 
  -d '[5.458,5.8064,6.018,6.0702,5.9472,5.6409,5.1517,4.4888,3.6699,2.7207,1.6732,0.5646,-0.5646,-1.6732,-2.7207,-3.6699,-4.4888,-5.1517,-5.6409,-5.9472,-6.0702,-6.018,-5.8064,-5.458,-5,-4.4632,-3.8794,-3.2798,-2.6929,-2.143,-1.6488,-1.2225,-0.8695,-0.5879,-0.3695,-0.2007,-0.0633,0.0633,0.2007,0.3695,0.5879,0.8695,1.2225,1.6488,2.143,2.6929,3.2798,3.8794,4.4632,5,5.458,5.8064,6.018,6.0702,5.9472,5.6409,5.1517,4.4888,3.6699,2.7207,1.6732,0.5646,-0.5646,-1.6732,-2.7207,-3.6699,-4.4888,-5.1517,-5.6409,-5.9472,-6.0702,-6.018,-5.8064,-5.458,-5,-4.4632,-3.8794,-3.2798,-2.6929,-2.143,-1.6488,-1.2225,-0.8695,-0.5879,-0.3695,-0.2007,-0.0633,0.0633,0.2007,0.3695,0.5879,0.8695,1.2225,1.6488,2.143,2.6929,3.2798,3.8794,4.4632,5,5.458]' 
  'https://api.marketcycles.online/api/CycleScanner?amplitudeMulti=1.0&bartelsLimit=49&minCycleLength=5&maxCycleLength=300&sortByStrength=true&includeSpectrum=false&humanReadableText=false&api_Key=aaaa'

这表明文档在建议datapoints值被命名时是在撒谎。事实并非如此。这很可能是导致您的错误的原因。

我通过curlconverter运行原始的、生成的curl命令行，它以httr模板的形式提供了以下内容：

代码语言：javascript
复制
httr::VERB(
  verb = "POST", 
  url = "https://api.marketcycles.online/api/CycleScanner",
  httr::add_headers(Accept = "application/json"),
  body = "[5.458,5.8064,6.018,6.0702,5.9472,5.6409,5.1517,4.4888,3.6699,2.7207,1.6732,0.5646,-0.5646,-1.6732,-2.7207,-3.6699,-4.4888,-5.1517,-5.6409,-5.9472,-6.0702,-6.018,-5.8064,-5.458,-5,-4.4632,-3.8794,-3.2798,-2.6929,-2.143,-1.6488,-1.2225,-0.8695,-0.5879,-0.3695,-0.2007,-0.0633,0.0633,0.2007,0.3695,0.5879,0.8695,1.2225,1.6488,2.143,2.6929,3.2798,3.8794,4.4632,5,5.458,5.8064,6.018,6.0702,5.9472,5.6409,5.1517,4.4888,3.6699,2.7207,1.6732,0.5646,-0.5646,-1.6732,-2.7207,-3.6699,-4.4888,-5.1517,-5.6409,-5.9472,-6.0702,-6.018,-5.8064,-5.458,-5,-4.4632,-3.8794,-3.2798,-2.6929,-2.143,-1.6488,-1.2225,-0.8695,-0.5879,-0.3695,-0.2007,-0.0633,0.0633,0.2007,0.3695,0.5879,0.8695,1.2225,1.6488,2.143,2.6929,3.2798,3.8794,4.4632,5,5.458]",
  encode = "json", 
  query = list(
    amplitudeMulti = "1.0",
    bartelsLimit = "49",
    minCycleLength = "5",
    maxCycleLength = "300",
    sortByStrength = "true",
    includeSpectrum = "false",
    humanReadableText = "false",
    api_Key = "aaaa"
  )
)

它比要求的b/c更冗长，它是以编程方式生成的。要将其放入您的原始代码中：

代码语言：javascript
复制
httr::POST(
  url = "https://api.marketcycles.online/api/CycleScanner",
  httr::accept_json()
  encode = "json", 
  body = jsonlite::toJSON(val),
  query = list(
    amplitudeMulti = "1.0",
    bartelsLimit = "49",
    minCycleLength = "5",
    maxCycleLength = "300",
    sortByStrength = "true",
    includeSpectrum = "false",
    humanReadableText = "false",
    api_Key = "aaaa"
  )
)

也许行得通。再一次，我只是去了Swagger，不能测试它。您还可以删除query位中的所有默认值。我喜欢在构建与API接口的包时传递它们。

票数 0
EN

Stack Overflow用户

发布于 2018-09-28 10:30:03

找到了解决方案。这是hrbrmstr建议的代码的一些调整。以下代码可以正常工作

代码语言：javascript
复制
httr::POST(
  url = "https://api.marketcycles.online/api/CycleScanner",
  httr::content_type_json(), # needed to add this
  httr::accept_json(),
  body =jsonlite::toJSON(val),
  # encode = "json", # needed to delete this 
  query = list(
    amplitudeMulti = "1.0",
    bartelsLimit = "49",
    minCycleLength = "5",
    maxCycleLength = "300",
    sortByStrength = "true",
    includeSpectrum = "false",
    humanReadableText = "false",
    api_Key = "wtt****")
)

谢谢你的帮助。

票数 0
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/52510792

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