XPath How to retrieve the value of a table cell from html document

问题

I have a html document and somewhere inside the doc is below a table, I can get the table rows and java DOM objects. What is not clear to me is how to extract the value of the table cell when the value is a string and also when it is a binary resource?

I am using code like:

  XPath xpath;
   XPathExpression expr;
   NodeList nodes=null;
   // Use XPath to obtain whatever you want from the (X)HTML
   try{

      xpath = XPathFactory.newInstance().newXPath();
      //<table class="data">

      NodeList list = doc.getElementsByTagName("table");
     // Node node = list.item(0); 
     //System.out.println(node.getTextContent());
    //String textContent=node.getTextContent();

    expr = xpath.compile("//table/tr/td");
    nodes = (NodeList)expr.evaluate(doc, XPathConstants.NODESET);

and loopiong like:

     for (int i = 0; i < nodes.getLength(); i++) {

       Node ln = list.item(i);
       String lnText=ln.toString();
       NodeList rowElements=ln.getChildNodes();
       Node one=rowElements.item(0);

       String oneText=one.toString();
       String nodeName=one.getNodeName();
       String valOne = one.getNodeValue();

But I am not seeing the values in the table.

 <table class="data">
 <tr><td>ImageName1</td><td width="50"></td><td><img src="/images/036000291452" alt="036000291452" /></td></tr>
 <tr><td>ImageName2</td><td width="50"></td><td><img src="/images/36000291452" alt="36000291452" /></td></tr>
 <tr><td>Description</td><td></td><td>Time Magazine</td></tr>
 <tr><td>Size/Weight</td><td></td><td>14 Issues</td></tr>
 <tr><td>Issuing Country</td><td></td><td>United States</td></tr>
  </table>

回答1:

This XPath expression:

/*/tr[1]/td[1]

selects the td element (in no namespace) that is the first child of the first tr child of the top element (table) of the provided XML document.

The XPath expression:

/*/tr[1]/td[2]

selects the td element (in no namespace) that is the second child of the first tr child of the top element (table) of the provided XML document.

In general:

/*/tr[$m]/td[$n]

selects the td element (in no namespace) that is the $n-th child of the $m-th tr child of the top element (table) of the provided XML document. Just replace $m and $n with the desired integer values.

You can use the standard XPath function string() to obtain their string value:

string(/*/tr[$m]/td[$n])

evaluates to the string value of the td element (in no namespace) that is the $n-th child of the $m-th tr child of the top element (table) of the provided XML document.

回答2:

Use a path like "string(//td)" to get the string contents of each cell. For linked resources, you will need to use something like "//td/img/@src" to get the URLs, then canonicalize them relative to the source url, and fetch te resulting URL from the network.

来源：https://stackoverflow.com/questions/5931352/xpath-how-to-retrieve-the-value-of-a-table-cell-from-html-document

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