使用YQL多查询& XPath解析HTML，如何逃避嵌套引号？ [英] Using YQL multi-query & XPath to parse HTML, how to escape nested quotes?

问题描述

  SELECT * 
 FROM query.multi 
 WHERE queries =
 SELECT * 
 FROM html 
 WHERE url ='http：//www.stumbleupon.com/url/http：//www.guildwars2 .com'
 AND xpath ='// li [@ class = \listLi\] / div [@ class = \views\] / a / span'; 
 SELECT * 
 FROM xml 
 WHERE url ='http：//services.digg.com/1.0/endpoint？method = story.getAll& link = http：//www.guildwars2.com'; 
 SELECT * 
 FROM json 
 WHERE url ='http：//api.tweetmeme.com/url_info.json？url = http：//www.guildwars2.com'; 
 SELECT * 
 FROM xml 
 WHERE url ='http：//api.facebook.com/restserver.php？method = links.getStats& urls = http：//www.guildwars2.com'; 
 SELECT * 
 FROM json 
 WHERE url ='http：//www.reddit.com/button_info.json？url = http：//www.guildwar s2.com'
  

具体来说这行，

b $ b

由于引用问题，我必须将它们三层嵌套，我已经用完了报价字符使用。我没有成功尝试过以下变体：

  //没有属性引用
 xpath ='// li [ @ class = listLi] / div [@ class = views] / a / span'
 
 //尝试引用属性w /反斜杠&单引号
 xpath ='// li [@ class = \'listLi\'] / div [@ class = \'views\'] / a / span'
 
 //尝试引用属性w /反斜杠&双引号
 xpath ='// li [@ class = \listLi\] / div [@ class = \views\] / a / span'
 
 //尝试用双引号引用属性，如SQL 
 xpath ='// li [@class =''listLi''] / div [@class =''views''] / a / span '
 
 //尝试用双引号引用属性，如SQL 
 xpath ='// li [@class =listLi] / div [@ class = views] / a / span'
 
 //尝试用引号实体引用属性
 xpath ='// li [@ class =& quot; listLi& quot;] / div [@ class =&views&] / a / span'
 
 //尝试用反斜杠&双引号
 xpath = \// li [@ class ='listLi'] / div [@ class ='views'] / a / span \
 
 // try用双引号环绕XPath 
 xpath =// li [@ class ='listLi'] / div [@ class ='views'] / a / span
  

所有没有成功。

我没有看到有关转义XPath字符串，但是我发现的所有东西似乎都是使用concat的变体（这不会有帮助，因为或不可用）或html实体。不使用引号的属性不会抛出错误，但是失败，因为它不是我需要实际的XPath字符串。

我在YQL文档中没有看到有关如何处理转义的任何内容，我知道这是多么边缘希望他们会有一些逃避指南。

解决方案

你需要逃避任何用XPath查询划定的字符双反斜杠 ...换句话说：

  SELECT * FROM query.multi 
 WHERE queries =
 SELECT * 
 FROM html 
 WHERE url =' http://www.stumbleupon.com/url/http://www.guildwars2.com'
 AND xpath ='// li [@ class = \\'listLi\\'] /的div [@类= \\'views\\ '] /一个/跨度'; 
 SELECT * 
 FROM xml 
 WHERE url ='http：//services.digg.com/1.0/endpoint？method = story.getAll& link = http：//www.guildwars2。 com公司; 
 SELECT * 
 FROM json 
 WHERE url ='http：//api.tweetmeme.com/url_info.json？url = http：//www.guildwars2.com'; 
 SELECT * 
 FROM xml 
 WHERE url ='http：//api.facebook.com/restserver.php？method = links.getStats& urls = http：//www.guildwars2。 com公司; 
 SELECT * 
 FROM json 
 WHERE url ='http：//www.reddit.com/button_info.json？url = http：//www.guildwars2.com'
  

^{（在YQL控制台中尝试此操作）}

The title is more complicated than it has to be, here's the problem query.

SELECT * 
FROM query.multi 
WHERE queries="
    SELECT * 
        FROM html 
        WHERE url='http://www.stumbleupon.com/url/http://www.guildwars2.com' 
        AND xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span';
    SELECT * 
        FROM xml 
        WHERE url='http://services.digg.com/1.0/endpoint?method=story.getAll&link=http://www.guildwars2.com';
    SELECT * 
        FROM json 
        WHERE url='http://api.tweetmeme.com/url_info.json?url=http://www.guildwars2.com';
    SELECT * 
        FROM xml 
        WHERE url='http://api.facebook.com/restserver.php?method=links.getStats&urls=http://www.guildwars2.com';
    SELECT * 
        FROM json 
        WHERE url='http://www.reddit.com/button_info.json?url=http://www.guildwars2.com'"

Specifically this line,

xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span'

It's problematic because of the quoting, I have to nest them three levels deep and I've run out of quote characters to use. I've tried the following variations without success:

//no attribute quoting
xpath='//li[@class=listLi]/div[@class=views]/a/span' 

//try to quote attribute w/ backslash & single quote
xpath='//li[@class=\'listLi\']/div[@class=\'views\']/a/span'

//try to quote attribute w/ backslash & double quote
xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span'

//try to quote attribute with double single quotes, like SQL
xpath='//li[@class=''listLi'']/div[@class=''views'']/a/span'

//try to quote attribute with double double quotes, like SQL
xpath='//li[@class=""listLi""]/div[@class=""views""]/a/span'

//try to quote attribute with quote entities
xpath='//li[@class="listLi"]/div[@class="views"]/a/span'

//try to surround XPath with backslash & double quote
xpath=\"//li[@class='listLi']/div[@class='views']/a/span\"

//try to surround XPath with double double quote
xpath=""//li[@class='listLi']/div[@class='views']/a/span""

All without success.

I don't see much out there about escaping XPath strings but everything I've found seems to be variations on using concat (which won't help because neither ' nor " are available) or html entities. Not using quotes for the attributes doesn't throw an error but fails because it's not the actual XPath string I need.

I don't see anything in the YQL docs about how to handle escaping. I'm aware of how edge-casey this is but was hoping they'd have some sort of escaping guide.

解决方案

You need to escape whatever character is delimiting your XPath query with a double backslash... in other words:

SELECT * FROM query.multi 
WHERE queries="
    SELECT * 
        FROM html 
        WHERE url='http://www.stumbleupon.com/url/http://www.guildwars2.com' 
        AND xpath='//li[@class=\\'listLi\\']/div[@class=\\'views\\']/a/span';
    SELECT * 
        FROM xml 
        WHERE url='http://services.digg.com/1.0/endpoint?method=story.getAll&link=http://www.guildwars2.com';
    SELECT * 
        FROM json 
        WHERE url='http://api.tweetmeme.com/url_info.json?url=http://www.guildwars2.com';
    SELECT * 
        FROM xml 
        WHERE url='http://api.facebook.com/restserver.php?method=links.getStats&urls=http://www.guildwars2.com';
    SELECT * 
        FROM json 
        WHERE url='http://www.reddit.com/button_info.json?url=http://www.guildwars2.com'"

^{(try this in the YQL console)}

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