以编程方式在R中抓取响应头

Question

我正在尝试访问突出显示的响应标题:下面的屏幕截图中的位置文本仅使用R及其基于curl的webscraping库.通过访问http://www.worldvaluessurvey.org/WVSDocumentationWVL.jsp,点击任何数据文件的下载,并填写协议表单,可以轻松地在任何Web浏览器中找到这一点.下载在Web浏览器中自动开始.

我相信获取有效cookie的唯一方法是library(curlconverter)(参见如何使用R下载半破javascript asp函数后面的文件)但该答案似乎不足以以编程方式确定文件的http url,只有在已知的压缩文件下载才能下载.

我在下面用不同的httr和curlconverter代码粘贴了一些代码,但我在这里遗漏了一些东西.同样,唯一的目标是以编程方式完全确定R(跨平台)内的突出显示文本.

library(curlconverter)
library(httr)

browserPOST <-
    "curl 'http://www.worldvaluessurvey.org/AJDownload.jsp'
    -H 'Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8'
    -H 'Accept-Encoding:gzip, deflate'
    -H 'Accept-Language:en-US,en;q=0.8'
    -H 'Cache-Control:max-age=0'
    --compressed -H 'Connection:keep-alive'
    -H 'Content-Length:188'
    -H 'Content-Type:application/x-www-form-urlencoded'
    -H 'Cookie:ASPSESSIONIDCASQAACD=IBLGBFOAEHFILMMJJCFEOEMI; JSESSIONID=50DABDEDD0B2FC370C415B4BD1855260; __atuvc=13%7C45; __atuvs=58224f37d312c42400c'
    -H 'Host:www.worldvaluessurvey.org'
    -H 'Origin:http://www.worldvaluessurvey.org'
    -H 'Referer:http://www.worldvaluessurvey.org/AJDownloadLicense.jsp'
    -H 'Upgrade-Insecure-Requests:1'
    -H 'User-Agent:Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36'"

form_data <-
    list( 
        ulthost = "WVS" ,
        CMSID = "" ,
        LITITLE = "" ,
        LINOMBRE = "fas" ,
        LIEMPRESA = "asf" ,
        LIEMAIL = "asdf" ,
        LIPROJECT = "asfd" ,
        LIUSE = "1" ,
        LIPURPOSE = "asdf" ,
        LIAGREE = "1" ,
        DOID = "3996" ,
        CndWAVE = "-1" ,
        SAID = "-1" ,
        AJArchive = "WVS Data Archive" ,
        EdFunction = "" ,
        DOP = "" 
    )   



getDATA <- (straighten(browserPOST) %>% make_req)[[1]]()

a <- VERB(verb = "POST", url = "http://www.worldvaluessurvey.org/AJDownload.jsp", 
    httr::add_headers(Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8", 
        `Accept-Encoding` = "gzip, deflate", `Accept-Language` = "en-US,en;q=0.8", 
        `Cache-Control` = "max-age=0", Connection = "keep-alive", 
        `Content-Length` = "188", Host = "www.worldvaluessurvey.org", 
        Origin = "http://www.worldvaluessurvey.org", Referer = "http://www.worldvaluessurvey.org/AJDownloadLicense.jsp", 
        `Upgrade-Insecure-Requests` = "1", `User-Agent` = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36"), 
    httr::set_cookies(`Cookie:ASPSESSIONIDCASQAACD` = "IBLGBFOAEHFILMMJJCFEOEMI", 
        JSESSIONID = "50DABDEDD0B2FC370C415B4BD1855260", `__atuvc` = "13%7C45", 
        `__atuvs` = "58224f37d312c42400c"), encode = "form",body=form_data)

Answer 1

这是一个很好的挑战!

该问题与R语言无关.如果我们只是尝试将一些数据发布到下载脚本,我们将在任何语言中获得相同的结果.我们必须在这里处理某种安全"模式".该站点限制用户检索文件URL,并要求用户填写带有数据的表单以提供这些链接.如果浏览器可以检索这些链接,那么我们也可以编写正确的HTTP调用.事实上,我们需要确切地知道我们必须做出哪些电话.为了找到这个,我们需要看到每当有人点击下载时网站所做的各个调用.以下是我在成功通话前发现的几个电话302 AJDownload.jsp POST:

我们可以清楚地看到它,如果我们查看AJDocumentation.jsp源代码,它会使用jQuery进行这些调用$.get:

$.get("http://ipinfo.io?token=xxxxxxxxxxxxxx", function (response) {
    var geodatos=encodeURIComponent(response.ip+"\t"+response.country+"\t"+response.postal+"\t"+
    response.loc+"\t"+response.region+"\t"+response.city+"\t"+
    response.org);

    $.get("jdsStatJD.jsp?ID="+geodatos+
        "&url=http%3A%2F%2Fwww.worldvaluessurvey.org%2FAJDocumentation.jsp&referer=null&cms=Documentation",
        function (resp2) {
    });
}, "jsonp");

然后,下面的几个调用,我们可以看到成功POST /AJDownload.jsp的状态302 Moved Temporarily和Location响应标头中的想要:

HTTP/1.1 302 Moved Temporarily
Content-Length: 0
Content-Type: text/html
Location: http://www.worldvaluessurvey.org/wvsdc/CO00001/F00003724-WVS_Longitudinal_1981-2014_stata_dta_v_2015_04_18.zip
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Thu, 01 Dec 2016 16:24:37 GMT

所以,这是这个网站的安全机制.它使用ipinfo.io存储有关其IP,位置甚至ISP组织的访问者信息,就在用户即将通过单击链接启动下载之前.接收这些数据的脚本是/jdsStatJD.jsp.我没有使用ipinfo.io,也没有使用它们的API密钥(将它隐藏在我的屏幕截图中)而是创建了一个虚拟的有效数据序列,只是为了验证请求.根本不需要"受保护"文件的发布表单数据.可以在不发布这些数据的情况下下载文件.

此外,该curlconverter库不是必需的.我们所要做的就是简单,GET并POST使用httr库请求.我要指出的一个重要部分是,为了防止httr POST函数跟随我们上次调用时Location收到302状态的标题,我们需要使用配置设置config(followlocation = FALSE),这当然会阻止它跟随Location并让我们Location从中获取标题.

OUTPUT

我的R脚本可以从命令行运行,它可以接受DOID参数的数值来获取所需的文件.例如,如果我们想获取文件的链接WVS_Longitudinal_1981-2014_stata_dta_v_2015_04_18,那么我们必须在使用以下命令调用它时将其DOID(即3724)添加到脚本的末尾Rscript:

Rscript wvs_fetch_downloads.r 3724
[1] "http://www.worldvaluessurvey.org/wvsdc/CO00001/F00003724-WVS_Longitudinal_1981-2014_stata_dta_v_2015_04_18.zip"

我创建了一个R函数,通过传递以下内容来获取所需的每个文件位置DOID:

getFileById <- function(fileId)

您可以删除命令行参数解析并通过DOID直接传递来使用该函数:

#args <- commandArgs(TRUE)
#if(length(args) == 0) {
#   print("No file id specified. Use './script.r ####'.")
#   quit("no")
#}

#fileId <- args[1]
fileId <- "3724"

# DOID=3843 : WVS_EVS_Integrated_Dictionary_Codebook v_2014_09_22 (Excel)
# DOID=3844 : WVS_Values Surveys Integrated Dictionary_TimeSeries_v_2014-04-25 (Excel)
# DOID=3725 : WVS_Longitudinal_1981-2014_rdata_v_2015_04_18
# DOID=3996 : WVS_Longitudinal_1981-2014_sas_v_2015_04_18
# DOID=3723 : WVS_Longitudinal_1981-2014_spss_v_2015_04_18
# DOID=3724 : WVS_Longitudinal_1981-2014_stata_dta_v_2015_04_18

getFileById(fileId)

最终的R工作脚本

library(httr)

getFileById <- function(fileId) {
    response <- GET(
        url = "http://www.worldvaluessurvey.org/AJDocumentation.jsp?CndWAVE=-1", 
        add_headers(
            `Accept` = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8", 
            `Accept-Encoding` = "gzip, deflate",
            `Accept-Language` = "en-US,en;q=0.8", 
            `Cache-Control` = "max-age=0",
            `Connection` = "keep-alive", 
            `Host` = "www.worldvaluessurvey.org", 
            `User-Agent` = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0",
            `Content-type` = "application/x-www-form-urlencoded",
            `Referer` = "http://www.worldvaluessurvey.org/AJDownloadLicense.jsp", 
            `Upgrade-Insecure-Requests` = "1"))

    set_cookie <- headers(response)$`set-cookie`
    cookies <- strsplit(set_cookie, ';')
    cookie <- cookies[[1]][1]

    response <- GET(
        url = "http://www.worldvaluessurvey.org/jdsStatJD.jsp?ID=2.72.48.149%09IT%09undefined%0941.8902%2C12.4923%09Lazio%09Roma%09Orange%20SA%20Telecommunications%20Corporation&url=http%3A%2F%2Fwww.worldvaluessurvey.org%2FAJDocumentation.jsp&referer=null&cms=Documentation", 
        add_headers(
            `Accept` = "*/*", 
            `Accept-Encoding` = "gzip, deflate",
            `Accept-Language` = "en-US,en;q=0.8", 
            `Cache-Control` = "max-age=0",
            `Connection` = "keep-alive", 
            `X-Requested-With` = "XMLHttpRequest",
            `Host` = "www.worldvaluessurvey.org", 
            `User-Agent` = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0",
            `Content-type` = "application/x-www-form-urlencoded",
            `Referer` = "http://www.worldvaluessurvey.org/AJDocumentation.jsp?CndWAVE=-1",
            `Cookie` = cookie))

    post_data <- list( 
        ulthost = "WVS",
        CMSID = "",
        CndWAVE = "-1",
        SAID = "-1",
        DOID = fileId,
        AJArchive = "WVS Data Archive",
        EdFunction = "",
        DOP = "",
        PUB = "")  

    response <- POST(
        url = "http://www.worldvaluessurvey.org/AJDownload.jsp", 
        config(followlocation = FALSE),
        add_headers(
            `Accept` = "*/*", 
            `Accept-Encoding` = "gzip, deflate",
            `Accept-Language` = "en-US,en;q=0.8", 
            `Cache-Control` = "max-age=0",
            `Connection` = "keep-alive",
            `Host` = "www.worldvaluessurvey.org",
            `User-Agent` = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0",
            `Content-type` = "application/x-www-form-urlencoded",
            `Referer` = "http://www.worldvaluessurvey.org/AJDocumentation.jsp?CndWAVE=-1",
            `Cookie` = cookie),
        body = post_data,
        encode = "form")

    location <- headers(response)$location
    location
}

args <- commandArgs(TRUE)
if(length(args) == 0) {
    print("No file id specified. Use './script.r ####'.")
    quit("no")
}

fileId <- args[1]

# DOID=3843 : WVS_EVS_Integrated_Dictionary_Codebook v_2014_09_22 (Excel)
# DOID=3844 : WVS_Values Surveys Integrated Dictionary_TimeSeries_v_2014-04-25 (Excel)
# DOID=3725 : WVS_Longitudinal_1981-2014_rdata_v_2015_04_18
# DOID=3996 : WVS_Longitudinal_1981-2014_sas_v_2015_04_18
# DOID=3723 : WVS_Longitudinal_1981-2014_spss_v_2015_04_18
# DOID=3724 : WVS_Longitudinal_1981-2014_stata_dta_v_2015_04_18

getFileById(fileId)