Question

我正在努力抓取依赖.atomsvc文件的公共数据源，以允许用户在Excel中设置数据Feed。我使用XML库提取URL，在R中构建了一个非常脆弱的解析器。我想知道如何在xml2中完成这项工作（最好以更简洁和优雅的方式）

以下是我使用XML库

的方式

'constants'

据我所知，xml2版本

# Crystal Reports Parser Sample
library(XML)
library(dplyr)

# Get the .atomsvc file from the Export to Data Feed Option on the PA DEP website
pa_string <- '<?xml version="1.0" encoding="utf-8" standalone="yes"?><service xmlns:atom="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xmlns="http://www.w3.org/2007/app"><workspace><atom:title>Oil_Gas_Well_Production</atom:title><collection href="http://www.depreportingservices.state.pa.us/ReportServer?%2FOil_Gas%2FOil_Gas_Well_Production&amp;P_PERIOD_ID=198&amp;P_COUNTY%3Aisnull=True&amp;P_CLIENT%3Aisnull=True&amp;P_PERMIT_NUM%3Aisnull=True&amp;P_OGO_NUM%3Aisnull=True&amp;P_PRODUCING%3Aisnull=True&amp;rs%3AParameterLanguage=&amp;rs%3ACommand=Render&amp;rs%3AFormat=ATOM&amp;rc%3ADataFeed=xAx0x2"><atom:title>Tablix1</atom:title></collection></workspace></service>'

pa_list <- pa_string %>% xmlParse() %>% xmlToList()
# Extract the URL
URL <- URLdecode(pa_list$workspace$collection$.attrs)

我不知道如何从这里提取URL，或者如果这是考虑如何思考这个问题的正确方法。任何帮助都将非常感激！

Answer 1

这是一种方法，通过从指定节点中提取属性：

library(xml2)
library(tidyverse)

pa_string <- '<?xml version="1.0" encoding="utf-8" standalone="yes"?><service xmlns:atom="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xmlns="http://www.w3.org/2007/app"><workspace><atom:title>Oil_Gas_Well_Production</atom:title><collection href="http://www.depreportingservices.state.pa.us/ReportServer?%2FOil_Gas%2FOil_Gas_Well_Production&amp;P_PERIOD_ID=198&amp;P_COUNTY%3Aisnull=True&amp;P_CLIENT%3Aisnull=True&amp;P_PERMIT_NUM%3Aisnull=True&amp;P_OGO_NUM%3Aisnull=True&amp;P_PRODUCING%3Aisnull=True&amp;rs%3AParameterLanguage=&amp;rs%3ACommand=Render&amp;rs%3AFormat=ATOM&amp;rc%3ADataFeed=xAx0x2"><atom:title>Tablix1</atom:title></collection></workspace></service>'

 pa_string %>% 
  read_xml() %>% 
  xml_find_all("//*[name()='collection']")%>%
  xml_attr("href") 
#output
[1] "http://www.depreportingservices.state.pa.us/ReportServer?%2FOil_Gas%2FOil_Gas_Well_Production&P_PERIOD_ID=198&P_COUNTY%3Aisnull=True&P_CLIENT%3Aisnull=True&P_PERMIT_NUM%3Aisnull=True&P_OGO_NUM%3Aisnull=True&P_PRODUCING%3Aisnull=True&rs%3AParameterLanguage=&rs%3ACommand=Render&rs%3AFormat=ATOM&rc%3ADataFeed=xAx0x2"

xpath:

#// - Recursive descent; searches for the specified element at any depth. 
#* -  Matches any element node
#[ ] - Applies a filter pattern.
#name()='collection' - self explanatory

更短：

pa_string %>% 
  read_xml() %>% 
  xml_find_all("//@href") #select all attributes with name `href`

因为只有一个带有属性的元素，所以也可以这样做：

pa_string %>% 
  read_xml() %>% 
  xml_find_all("//@*") #Matches any attribute node

xml2从.atomsvc文件中提取URL

1 个答案:

xml2从.atomsvc​​文件中提取URL

1 个答案:

xml2从.atomsvc文件中提取URL