java - 错误 XPATH KML JDOM

Question

我正在尝试使用 JDOM(XPATH) 读取 KML。该错误不会被异常捕获，仅当鼠标悬停在 XPath.newInstance("//Kml/Document/Placemark/LookAt"); 行的代码上时，我看到的错误是:

XPath.newInstance("//Kml/Document/Placemark/LookAt"); = >Exception occurred in target VM: WEB9031: WebappClassLoader unable to load resource [java.lang.ExceptionInInitializerError], because it has not yet been started, or was already stopped<

我的代码:

public void lerKML() throws Exception {
    String path = req.getRealPath("/Usuarios/" + pe.getEmail() + "/"+ pe.getTitulo() + "/" + pe.getNomeArquivoKMLZ());

    SAXBuilder builder = new SAXBuilder();
    Document document = builder.build(new File(path));

    XPath xPath = XPath.newInstance("//Kml/Document/Placemark/LookAt");

    Element node = (Element) xPath.selectSingleNode(document.getRootElement());
    ...
}

示例 KML 文件:

<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom">
<Document>
<Placemark>
    <name>teste</name>
    <LookAt>
        <longitude>-47.82056628282606</longitude>
        <latitude>-15.78921645504241</latitude>
        <altitude>0</altitude>
        <heading>0</heading>
        <tilt>0</tilt>
        <range>668.1932383230591</range>
    </LookAt>
</Placemark>
</Document>
</Kml>

Answer 1

您看到的错误，看起来像是网络应用程序部署问题。如果您发布带有原因 的完整堆栈跟踪，我可能会进一步提供帮助。您是否已将所有必需的 jar 包含到项目中？

但是，还有一些其他问题需要解决，否则代码将无法按预期工作。

首先，KML 文件无效。结束标记 </Kml>与开始标签 <kml> 不匹配. XML 区分大小写。

其次，您使用的 XPath 不是 namespace意识到的。假定没有前缀的标记位于默认 namespace 中。您需要添加此默认命名空间。

我制作了一个加载和解析以下 KML(已更正)文件(另存为 test.kml)的小演示

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom">
<Document>
    <Placemark>
      <name>teste</name>
      <LookAt>
        <longitude>-47.82056628282606</longitude>
        <latitude>-15.78921645504241</latitude>
        <altitude>0</altitude>
        <heading>0</heading>
        <tilt>0</tilt>
        <range>668.1932383230591</range>
      </LookAt>
    </Placemark>
</Document>
</kml>

演示类(另存为ReadKml.java文件，与test.kml放在同一目录下)

import java.io.*;
import org.jdom.input.SAXBuilder;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.xpath.XPath;

public class ReadKml {
    public static void main(String args[]) throws Exception {
        File kmlFile = new File("test.kml");
        SAXBuilder builder = new SAXBuilder();
        Document document = builder.build(kmlFile);

        XPath xPath = XPath.newInstance("//k:kml/k:Document/k:Placemark/k:LookAt");
        xPath.addNamespace("k", document.getRootElement().getNamespaceURI());

        Element node = (Element) xPath.selectSingleNode(document.getRootElement());
        System.out.println(node.getName());
    }
}

demo要求JDOM在classpath下进行编译，例如在Windows上编译demo类型javac -cp jars\jdom.jar ReadKml.java .运行演示也需要 Jaxen，因此将其添加到类路径中，例如 java -cp .;jars\jdom.jar;jars\jaxen.jar ReadKml

这导致 System.output 为 LookAt ，这就是 Element.name() .

希望对您有所帮助。