java - 比 javax.xml.xpath 更快的 api 来解析 xml 的值？

Question

我正在使用 javax.xml.xpath 来搜索 xml 文件中的特定字符串，但是由于需要搜索的 xml 文件数量巨大，这比预期的。

是否有任何 java 支持的 api 比 javax.xml.xpath 更快或可用的最快？

Answer 1

正如 skaffman 指出的那样您需要确保尽可能高效地使用 javax.xml.xpath 库。如果您多次执行 XPath 语句，您需要确保将其编译成 XPathExpression。

XPathExpression xPathExpression = xPath.compile("/root/device/modelname");
nl = (NodeList) xPathExpression.evaluate(dDoc, XPathConstants.NODESET);

演示

在示例中，选项 #2 将比选项 #1 更快。

import java.io.File;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

public class Demo {

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

            NodeList nl;

            // OPTION #1
            XPath xPath = XPathFactory.newInstance().newXPath();
            nl = (NodeList) xPath.evaluate("root/device/modelname", dDoc, XPathConstants.NODESET);
            printResults(nl);
            nl = (NodeList) xPath.evaluate("/root/device/modelname", dDoc, XPathConstants.NODESET);
            printResults(nl);

            // OPTION #2
            XPathExpression xPathExpression = xPath.compile("/root/device/modelname");
            nl = (NodeList) xPathExpression.evaluate(dDoc, XPathConstants.NODESET);
            printResults(nl);
            nl = (NodeList) xPathExpression.evaluate(dDoc, XPathConstants.NODESET);
            printResults(nl);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void printResults(NodeList nl) {
        for(int x=0; x<nl.getLength(); x++) {
            System.out.println("the value is: " + nl.item(x).getTextContent());
        }
    }

}

输入.xml

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <blah>foo</blah>
  <device>
    <modelname>xbox</modelname>
  </device>
  <blah>bar</blah>
  <device>
    <modelname>wii</modelname>
  </device>
  <blah/>
</root>