XPATH中text()和string()的使用区别

<table style="WIDTH: 95.45%; BORDER-COLLAPSE: collapse; EMPTY-CELLS: show; MARGIN-LEFT: 4.55%; MARGIN-TOP: 2pt" cellspacing="0" cellpadding="4">
  <tbody>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> Diversified Income Series 
      (Service Class): Maximum long-term total return consistent with reasonable 
      risk. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> Emerging Markets Series (Service 
      Class): Long-term capital appreciation. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> Limited-Term Diversified Income 
      Series (Service Class): Maximum total return, consistent with reasonable 
      risk. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> REIT Series (Service Class): 
      Maximum long-term total return, with capital appreciation as a secondary 
      objective. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> Small Cap Value Series (Service 
      Class): Capital appreciation. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> Smid Cap Core Series (Service 
      Class): Long-term capital appreciation. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> U.S. Growth Series (Service 
      Class): Long-term capital appreciation. </td></tr>
  <tr style="PAGE-BREAK-INSIDE: avoid">
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 1.39%; VERTICAL-ALIGN: top; WHITE-SPACE: nowrap; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; PADDING-BOTTOM: 0pt; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 0pt; LINE-HEIGHT: 13pt; PADDING-RIGHT: 2pt">• 
    </td>
    <td style="FONT-SIZE: 10pt; TEXT-DECORATION: none; FONT-FAMILY: Arial Narrow; WIDTH: 98.61%; VERTICAL-ALIGN: top; TEXT-TRANSFORM: none; FONT-WEIGHT: normal; COLOR: #000000; PADDING-BOTTOM: 0pt; FONT-STYLE: normal; TEXT-ALIGN: left; PADDING-LEFT: 2pt; LINE-HEIGHT: 13pt">Delaware 
      VIP<sup style="FONT-SIZE: 85%; VERTICAL-ALIGN: text-top; TEXT-TRANSFORM: none; FONT-STYLE: normal"><font style="PADDING-LEFT: 1pt"></font>®</sup> Value Series (Service Class): 
      Long-term capital appreciation. </td></tr></tbody></table>

在上面的Html表格中，我们要抓出每个tr标签中第2个td的文本内容，一开始想到的XPATH语句是这么写的：

//td[contains(text(),':') and contains(text(),'(') and contains(text(),')') and (contains(text(),'Class') or contains(text(),'Shares'))]

结果发现提不出来，将text()函数改为string()函数，就可以提出来了：

//td[contains(string(),':') and contains(string(),'(') and contains(string(),')') and (contains(string(),'Class') or contains(string(),'Shares'))]

原文档中有些td标签文本有换行，而且可能还夹杂着其他子标签，这时候可能用text()提取不出来，可以改用string()，string()可以将所有子标签中的文本串成一起提出来，可以满足绝大部分时候的需求。