java - 如何使用 XPath 提取 XML 表数据

Question

<table index="1" title=" Final year marks of BIT students" ref="BIT results">
        <headings>
          <heading>Semester1</heading>
          <heading>Semester2</heading>
          <heading>Semester3</heading>
          <heading>Semester4</heading>
          <heading>Grade</heading>
          <heading>FYP</heading>
        </headings>
        <tablebody>
          <tablerow>
            <tablecell><item>10</item></tablecell>
            <tablecell><item>12</item></tablecell>
            <tablecell><item>13</item></tablecell>
            <tablecell><item>15</item></tablecell>
            <tablecell><item>B</item></tablecell>
            <tablecell><item>B</item></tablecell>
          </tablerow>
        </tablebody>
      </table>
      <table index="2" title="Final year marks of COM students" ref="COM results">
        <headings>
          <heading>Semester1</heading>
          <heading>Semester2</heading>
          <heading>Semester3</heading>
          <heading>Semester4</heading>
          <heading>Grade</heading>
          <heading>FYP</heading>
        </headings>
        <tablebody>
          <tablerow>
            <tablecell><item>15</item></tablecell>
            <tablecell><item>15</item></tablecell>
            <tablecell><item>15</item></tablecell>
            <tablecell><item>14</item></tablecell>
            <tablecell><item>A</item></tablecell>
            <tablecell><item>A</item></tablecell>
          </tablerow>
          <tablerow>
            <tablecell><item>10</item></tablecell>
            <tablecell><item>5</item></tablecell>
            <tablecell><item>9</item></tablecell>
            <tablecell><item>11</item></tablecell>
            <tablecell><item>C</item></tablecell>
            <tablecell><item>C</item></tablecell>
          </tablerow>
        </tablebody>
      </table>``

嗨，我是 Xpath 的新手。我需要使用 Xpath 提取 XML 表数据。这是我的 XML 代码。我已经尝试过，但无法获得成功的输出。

The output table would be like this 

semester1  semester2  semester3 semester4  grade  fyp
 10            11          13       12         A   B

有人知道解决这个问题的最佳方法吗？谢谢:)

Answer 1

首先，您的示例 XML 无效。您要么提供了两个单独的示例，要么缺少周围的父标记。

我假设了第二个并将示例包装在 <tables></tables> 中标签。

所以现在基于此...

<tables>
    <table index="1" title=" Final year marks of BIT students" ref="BIT results">
        <headings>
            <heading>Semester1</heading>
            <heading>Semester2</heading>
            <heading>Semester3</heading>
            <heading>Semester4</heading>
            <heading>Grade</heading>
            <heading>FYP</heading>
        </headings>
        <tablebody>
            <tablerow>
                <tablecell>
                    <item>10</item>
                </tablecell>
                <tablecell>
                    <item>12</item>
                </tablecell>
                <tablecell>
                    <item>13</item>
                </tablecell>
                <tablecell>
                    <item>15</item>
                </tablecell>
                <tablecell>
                    <item>B</item>
                </tablecell>
                <tablecell>
                    <item>B</item>
                </tablecell>
            </tablerow>
        </tablebody>
    </table>
    <table index="2" title="Final year marks of COM students" ref="COM results">
        <headings>
            <heading>Semester1</heading>
            <heading>Semester2</heading>
            <heading>Semester3</heading>
            <heading>Semester4</heading>
            <heading>Grade</heading>
            <heading>FYP</heading>
        </headings>
        <tablebody>
            <tablerow>
                <tablecell>
                    <item>15</item>
                </tablecell>
                <tablecell>
                    <item>15</item>
                </tablecell>
                <tablecell>
                    <item>15</item>
                </tablecell>
                <tablecell>
                    <item>14</item>
                </tablecell>
                <tablecell>
                    <item>A</item>
                </tablecell>
                <tablecell>
                    <item>A</item>
                </tablecell>
            </tablerow>
            <tablerow>
                <tablecell>
                    <item>10</item>
                </tablecell>
                <tablecell>
                    <item>5</item>
                </tablecell>
                <tablecell>
                    <item>9</item>
                </tablecell>
                <tablecell>
                    <item>11</item>
                </tablecell>
                <tablecell>
                    <item>C</item>
                </tablecell>
                <tablecell>
                    <item>C</item>
                </tablecell>
            </tablerow>
        </tablebody>
    </table>
</tables>

我能够使用...

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class TestXPath {

    public static void main(String[] args) {
        try {
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document doc = builder.parse(new File("Table.xml"));

            XPathFactory xFactory = XPathFactory.newInstance();
            XPath path = xFactory.newXPath();
            XPathExpression exp = path.compile("/tables/table");
            NodeList nlTables = (NodeList) exp.evaluate(doc, XPathConstants.NODESET);
            for (int tblIndex = 0; tblIndex < nlTables.getLength(); tblIndex++) {

                Node table = nlTables.item(tblIndex);
                Node nAtt = table.getAttributes().getNamedItem("title");
                System.out.println("Showing results for " + (nAtt == null ? "[Unknown]" : nAtt.getTextContent()));

                exp = path.compile("headings/heading");
                NodeList nlHeaders = (NodeList) exp.evaluate(table, XPathConstants.NODESET);
                Set<String> headers = new HashSet<String>(25);
                for (int index = 0; index < nlHeaders.getLength(); index++) {
                    headers.add(nlHeaders.item(index).getTextContent().trim());
                }

                for (String header : headers) {
                    System.out.printf("%-20s", header);
                }
                System.out.println("");

                exp = path.compile("tablebody/tablerow");
                NodeList nlRows = (NodeList) exp.evaluate(table, XPathConstants.NODESET);
                for (int index = 0; index < nlRows.getLength(); index++) {
                    Node rowNode = nlRows.item(index);
                    exp = path.compile("tablecell/item");
                    NodeList nlValues = (NodeList) exp.evaluate(rowNode, XPathConstants.NODESET);
                    List<String> values = new ArrayList<String>(25);
                    for (int valueIndex = 0; valueIndex < nlValues.getLength(); valueIndex++) {
                        values.add(nlValues.item(valueIndex).getTextContent().trim());
                    }
                    for (String value : values) {
                        System.out.printf("%-20s", value);
                    }
                    System.out.println("");
                }
                System.out.println("");
            }

        } catch (ParserConfigurationException exp) {
            exp.printStackTrace();
        } catch (SAXException | IOException | XPathExpressionException ex) {
            ex.printStackTrace();
        }
    }

}

生产...

Showing results for  Final year marks of BIT students
Semester1           Semester2           Semester3           Semester4           FYP                 Grade               
10                  12                  13                  15                  B                   B                   

Showing results for Final year marks of COM students
Semester1           Semester2           Semester3           Semester4           FYP                 Grade               
15                  15                  15                  14                  A                   A                   
10                  5                   9                   11                  C                   C   

基本上，您需要能够将每个部分分解为可管理的部分......

看看XPath Tutorial并阅读 SO 上关于 XPath 的几乎所有帖子；)