我想填写web form并提交查询并下载结果数据。某些字段可以选择下拉菜单或输入搜索查询,也可以将部分保留为空白(如果所有部分都保留为空白,则将下载整个数据库),单击“搜索并下载”按钮应提示文件下载。
[这是我根据this问题尝试过的方法(为“ Salmo salar”物种选择所有记录)。我使用浏览器(Opera)的“开发人员工具”检查页面元素并确定所有可能字段的名称:
library(httr)
url <- "https://nzffdms.niwa.co.nz/search"
fd <- list(
search_catchment_no_name = "",
search_river_lake = "",
search_sampling_locality = "",
search_fishing_method = "",
search_start_year = "",
search_end_year = "",
search_species = "Salmo salar", # species of interest
search_download_format = 1, # select csv file format
submit = "Search and Download"
)
POST(url, body = fd, encode = "form")
我曾希望这将导致下载一个csv文件(物种“ Salmo salar”的所有记录),但没有文件下载(但输出此文件(清单10,仅显示第一位):
Response [https://nzffdms.niwa.co.nz/search]
Date: 2019-10-02 23:35
Status: 200
Content-Type: text/html; charset=utf-8
Size: 19.1 kB
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; c...
<meta name="title" content="NZ Freshwater Fish Database...
<meta name="description" content="NIWA NZ Freshwater Fish...
<meta name="keywords" content="NIWA, NZ, Freshwater Fish" />
<meta name="language" content="en" />
<meta name="robots" content="index, follow />
...
我认为问题在于我如何调用Search and download
按钮,当检查网页时,大多数字段看起来像这样:
# end year field
<input maxlength="4" class="form-control" type="text" name="search[end_year]" id="search_end_year">
但是search and download
按钮元素没有name
或id
选项:
<input type="submit" value="Search and Download" class="btn btn-primary btn-md">
而且我刚刚注意到有一个隐藏字段,也许我需要定义它?
<input type="hidden" name="search[_csrf_token]" value="d1530f09c1ce8110b5163bd100cb0d67" id="search__csrf_token">
有关如何下载文件的任何建议,将不胜感激。
首先,检查website上的robots.txt。截至2019年10月3日已被注释掉。
然后阅读https://nzffdms.niwa.co.nz/terms和https://www.niwa.co.nz/freshwater-and-estuaries/nzffd/user-guide/tips上的条款和条件,并确保您遵守这些条款和条件。
并且节制以下请求也很重要。
检查所有条款和条件后,您可以使用下面的代码查询数据:
library(httr) library(xml2) gr <- GET("https://nzffdms.niwa.co.nz/search") doc <- read_html(content(gr, "text")) #doc <- read_html(gr) #this works as well getTbl <- function(x) { do.call(rbind, lapply(xml_find_all(doc, paste0(".//select[@name='search",x,"']/option")), function(n) data.frame(NAME=xml_text(n), VALUE=xml_attr(n, "value")))) } fishing_method <- getTbl("[fishing_method]") species <- getTbl("[species][]") csrf_token <- xml_attr(xml_find_all(doc, ".//input[@name='search[_csrf_token]']"), "value") fd <- list( "search[catchment_no_name]"="", "search[river_lake]"="", "search[sampling_locality]"="", "search[fishing_method]"="", "search[species][]"="", "search[species][]"=68, "search[start_year]"="", "search[end_year]"="", "search[download_format]"="1", "search[_csrf_token]"=csrf_token ) r <- POST("https://nzffdms.niwa.co.nz/doSearch", body=fd, encode="form") read.csv(text=content(r, "text", encoding="UTF-8"))
输出:
card m y catchname catch locality time org map east north altitude penet fishmeth effort pass spcode abund number minl maxl nzreach
1 3964 1 1981 Waiau R 797.49 Lake Gunn NA niwa d41 2122400 5581200 477 225 ang NA NA salsal NA NA NA NA 15006671
2 3965 1 1981 Waiau R 797.49 Lake Fergus NA niwa d41 2123700 5584400 483 229 ang NA NA salsal NA NA NA NA 15006092
3 15975 1 2003 Waiau R 797.40 Excelsior Creek 1330 niwa d44 2095800 5495800 190 94 efp 80 1 salsal NA 2 102 105 15030686
4 50772 1 1940 Waiau R 797.49 Upukerora River NA unk d43 2098500 5519900 210 146 unk NA NA salsal NA NA NA NA 15020897