XPath使用Nokogiri返回空数组
Ric*_*sta 1 ruby xpath mechanize nokogiri
我正在尝试使用Nokogiri,Mechanize和XPath解析页面,但是,无论我尝试什么,我都会收到一个空数组.
我在Chrome中检查了它并获得了XPath,然后尝试了多种方法来解析它,但总是收到一个空数组.
我试过了:
puts page.search('/html/body/div/table/tbody/tr[2]/td/table/tbody/tr[2]/td[2]').inspect
puts post_page.parser.xpath('/html/body/div/table/tbody/tr[2]/td/table/tbody/tr[2]/td[2]').inspect
puts post_page.parser.at_xpath('/html/body/div/table/tbody/tr[2]/td/table/tbody/tr[2]/td[2]').inspect
所有有和没有尾随"/文本"
这是我试图抓取的页面的来源:
<SCRIPT language="JavaScript">
<!--
document.cookie = "IV_JCT=%2FMPIS; path=/";
//-->
</SCRIPT>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My Schedule</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="-1">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my schedule">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<div align="center">
<strong>My Schedule</strong><br>as of Sun Feb 24 2013 06:43:09 PM CST<br><br>
<div align="left"><pre><br>Employee Name: Johnson Appleseed
Unit = 12345</pre>
<br>
</div>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td colspan="8" align="center"><b><font size="+1">Schedules may be subject to change based on business needs or demand</font></b></td>
</tr>
<tr><td>
<table border="4" bordercolor="#2D73B9" cellpadding="2" cellspacing="2" width="100%">
<tr bgcolor="#7C9BCF">
<td width="12%" align="center"><b>Sunday</b></td>
<td width="12%" align="center"><b>Monday</b></td>
<td width="12%" align="center"><b>Tuesday</b></td>
<td width="12%" align="center"><b>Wednesday</b></td>
<td width="12%" align="center"><b>Thursday</b></td>
<td width="12%" align="center"><b>Friday</b></td>
<td width="12%" align="center"><b>Saturday</b></td>
<td rowspan="2" width="12%" align="center"><b>Total weekly Hours</b></td>
</tr>
<tr bgcolor="#7C9BCF">
<td width="14%" align="center">2013-02-24</td>
<td width="14%" align="center">2013-02-25</td>
<td width="14%" align="center">2013-02-26</td>
<td width="14%" align="center">2013-02-27</td>
<td width="14%" align="center">2013-02-28</td>
<td width="14%" align="center">2013-03-01</td>
<td width="14%" align="center">2013-03-02</td>
</tr>
<tr bgcolor="#FFFFFF">
<td width="14%" align="left"><pre> </pre></td>
<td width="14%" align="left"><pre><b>Shift: </b>
5:30 PM - 9:00 PM
<b>Meal:</b>
- </pre></td>
<td width="14%" align="left"><pre> </pre></td>
<td width="14%" align="left"><pre> </pre></td>
<td width="14%" align="left"><pre> </pre></td>
<td width="14%" align="left"><pre><b>Shift: </b>
2:00 PM - 9:15 PM
<b>Meal:</b>
5:45 PM - 6:30 PM</pre></td>
<td width="14%" align="left"><pre><b>Shift: </b>
4:45 PM - 9:15 PM
<b>Meal:</b>
- </pre></td>
<td width="12%" align="center">14.5</td>
</tr>
<tr bgcolor="#FFFFFF">
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">3.5</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">6.5</td>
<td width="14%" align="center">4.5</td>
<td width="14%" align="center">Daily Hours</td>
</tr>
</table>
</td></tr>
<tr><td>
<table border="4" bordercolor="#2D73B9" cellpadding="2" cellspacing="2" width="100%">
<tr bgcolor="#7C9BCF">
<td width="12%" align="center"><b>Sunday</b></td>
<td width="12%" align="center"><b>Monday</b></td>
<td width="12%" align="center"><b>Tuesday</b></td>
<td width="12%" align="center"><b>Wednesday</b></td>
<td width="12%" align="center"><b>Thursday</b></td>
<td width="12%" align="center"><b>Friday</b></td>
<td width="12%" align="center"><b>Saturday</b></td>
<td rowspan="2" width="12%" align="center"><b>Total weekly Hours</b></td>
</tr>
<tr bgcolor="#7C9BCF">
<td width="14%" align="center">2013-03-03</td>
<td width="14%" align="center">2013-03-04</td>
<td width="14%" align="center">2013-03-05</td>
<td width="14%" align="center">2013-03-06</td>
<td width="14%" align="center">2013-03-07</td>
<td width="14%" align="center">2013-03-08</td>
<td width="14%" align="center">2013-03-09</td>
</tr>
<tr bgcolor="#FFFFFF">
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="12%" align="center">0.0</td>
</tr>
<tr bgcolor="#FFFFFF">
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">Daily Hours</td>
</tr>
</table>
</td></tr>
<tr><td>
<table border="4" bordercolor="#2D73B9" cellpadding="2" cellspacing="2" width="100%">
<tr bgcolor="#7C9BCF">
<td width="12%" align="center"><b>Sunday</b></td>
<td width="12%" align="center"><b>Monday</b></td>
<td width="12%" align="center"><b>Tuesday</b></td>
<td width="12%" align="center"><b>Wednesday</b></td>
<td width="12%" align="center"><b>Thursday</b></td>
<td width="12%" align="center"><b>Friday</b></td>
<td width="12%" align="center"><b>Saturday</b></td>
<td rowspan="2" width="12%" align="center"><b>Total weekly Hours</b></td>
</tr>
<tr bgcolor="#7C9BCF">
<td width="14%" align="center">2013-03-10</td>
<td width="14%" align="center">2013-03-11</td>
<td width="14%" align="center">2013-03-12</td>
<td width="14%" align="center">2013-03-13</td>
<td width="14%" align="center">2013-03-14</td>
<td width="14%" align="center">2013-03-15</td>
<td width="14%" align="center">2013-03-16</td>
</tr>
<tr bgcolor="#FFFFFF">
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="14%" align="left"><pre>Sched Not Posted</pre></td>
<td width="12%" align="center">0.0</td>
</tr>
<tr bgcolor="#FFFFFF">
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">0.0</td>
<td width="14%" align="center">Daily Hours</td>
</tr>
</table>
</td></tr>
<tr>
<td colspan="8" align="center"><b><font size="+1">Schedules may be subject to change based on business needs or demand</font></b></td>
</tr>
</table >
<p><br>
</p>
<p class="align_center" >
<input type=button value="Print this page" onClick="javascript:window.print();">
<input type=button value="Close This Window" onClick="javascript:window.close();">
</p>
</div>
</body>
</html>
请注意,在XPath访问器中,您需要tbody成为路径的一部分:
puts page.search('/html/body/div/table/tbody/tr[2]/td/table/tbody/tr[2]/td[2]').inspect
puts post_page.parser.xpath('/html/body/div/table/tbody/tr[2]/td/table/tbody/tr[2]/td[2]').inspect
puts post_page.parser.at_xpath('/html/body/div/table/tbody/tr[2]/td/table/tbody/tr[2]/td[2]').inspect
HTML没有tbody标记,导致查找失败.
尝试简化您的访问者.我通常从Nokogiri支持的CSS开始,然后,如果我无法到达那里,我切换到XPath.您的里程可能因此而异.
例如:
(rdb:1) puts doc.at('table table tr').to_html
输出:
<tr bgcolor="#7C9BCF">
<td width="12%" align="center"><b>Sunday</b></td>
<td width="12%" align="center"><b>Monday</b></td>
<td width="12%" align="center"><b>Tuesday</b></td>
<td width="12%" align="center"><b>Wednesday</b></td>
<td width="12%" align="center"><b>Thursday</b></td>
<td width="12%" align="center"><b>Friday</b></td>
<td width="12%" align="center"><b>Saturday</b></td>
<td rowspan="2" width="12%" align="center"><b>Total weekly Hours</b></td>
</tr>
这是获取列标题的更简单方法.
要获得第二行,您可以使用:
(rdb:1) puts doc.at('table table tr[2]').to_html
哪个让你:
<tr bgcolor="#7C9BCF">
<td width="14%" align="center">2013-02-24</td>
<td width="14%" align="center">2013-02-25</td>
<td width="14%" align="center">2013-02-26</td>
<td width="14%" align="center">2013-02-27</td>
<td width="14%" align="center">2013-02-28</td>
<td width="14%" align="center">2013-03-01</td>
<td width="14%" align="center">2013-03-02</td>
</tr>
要获取单元格内容,您可以使用:
(rdb:1) puts doc.search('table table tr[2] td').map(&:text)
哪个回报:
2013-02-24
2013-02-25
2013-02-26
2013-02-27
2013-02-28
2013-03-01
2013-03-02
2013-03-03
2013-03-04
2013-03-05
2013-03-06
2013-03-07
2013-03-08
2013-03-09
2013-03-10
2013-03-11
2013-03-12
2013-03-13
2013-03-14
2013-03-15
2013-03-16
注意这是如何返回两个表的标题.要将它限制在第一个表中,我们可以使用at而不是search.at返回第一个匹配节点,search返回一个NodeSet,就像一个数组.此外,search查看所有匹配的整个文档,与at行为不同.
此代码查找第一个表的第二行,然后遍历嵌入的单元格:
(rdb:1) puts doc.at('table table tr[2]').search('td').map(&:text)
2013-02-24
2013-02-25
2013-02-26
2013-02-27
2013-02-28
2013-03-01
2013-03-02
它更简单,更易于理解和维护.