错误XPATH KML JDOM

Question

我正在尝试用JDOM(XPATH)读取KML。错误不会被异常捕获，只有鼠标在XPath.newInstance("//Kml/Document/Placemark/LookAt");行的代码上捕获错误，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

您所看到的错误，看起来就像一个webapp部署问题。如果您发布完整的堆栈跟踪与原因，我可能可以帮助进一步。你把所有需要的罐子都包括到项目里了吗？

但是，还有一些其他的问题需要解决，否则代码将不能像预期的那样工作。

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

其次，您使用的XPath并不是命名空间感知的。没有前缀的标记被假定在默认名称空间中。您需要添加此默认命名空间。

我做了一个小演示，它加载并解析了以下KML (更正的)文件(另存为test.kml)

<?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(保存为一个名为ReadKml.java的文件，并放在与test.kml相同的目录中)

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());
    }
}

演示要求JDOM在类路径上进行编译，例如在Windows上编译演示类型javac -cp jars\jdom.jar ReadKml.java。运行演示程序也需要Jaxen，因此将其添加到类路径中，例如java -cp .;jars\jdom.jar;jars\jaxen.jar ReadKml

这导致了System.output of LookAt，这就是Element.name()。

我希望这能帮到你。