Question

我试图读取xml，我需要从每条道路获取相应的段，并将信息放在其他类中。

这是XML文件：

<section_list>  
 <road_section begin="n0" end="n1">
     <road>"E01"</road>
     <wind_speed>3 m/s</wind_speed>
      <segment_list>
         <segment id="01">
               <height>100</height>
              <number_vehicles>20</number_vehicles>
         </segment>
         <segment id="02">
              <height>148</height>
              <number_vehicles>20</number_vehicles>
         </segment>
      </segment_list>
 </road_section>
 <road_section begin="n0" end="n2">
     <road>"E01"</road>
     <wind_speed>3 m/s</wind_speed>
        <segment_list>
            <segment id="03">
                <height>100</height>
                <number_vehicles>100</number_vehicles>
            </segment>
         </segment_list>
 </road_section> 
</section_list>

当我运行程序时会发生的事情是，对于每条道路，他打印所有段，例如道路＆＃39; EO1＆＃39;当程序只打印段id = 01和id = 02时，程序会打印3段。

这是我的Java代码：

NodeList listSection = doc.getElementsByTagName("road_section");
for (int temp = 0; temp < listSection.getLength(); temp++) {
    Node nNode = listSection.item(temp);
    if (nNode.getNodeType() == Node.ELEMENT_NODE) {
        Element eElement = (Element) nNode;

        System.out.println("Begin : " + eElement.getAttribute("begin") + "\tEnd: " + eElement.getAttribute("end"));
        System.out.println("road : " + eElement.getElementsByTagName("road").item(0).getTextContent().replaceAll("\"", ""));
        System.out.println("wind_speed : " + eElement.getElementsByTagName("wind_speed").item(0).getTextContent().trim().replaceAll("m/s", ""));
    }
    for (int i = 0; i < 1; i++) {
        Element eElement = (Element) nNode;
        NodeList listaSegmentos = eElement.getElementsByTagName("segment_list").item(i).getChildNodes();
        for (int j = 0; j < listaSegmentos.getLength(); j++) {
            Node nodeseg = listaSegmentos.item(cont);
            if (nodeseg.getNodeType() == Node.ELEMENT_NODE) {
                Element el = (Element) nodeseg;
                System.out.println("\nSegment id : " + el.getAttribute("id"));
                System.out.println("height : " + el.getElementsByTagName("height").item(0).getTextContent().replaceAll("\"", ""));
                System.out.println("number_vehicles : " + el.getElementsByTagName("number_vehicles").item(0).getTextContent().trim());

            }
        }
    }
}

Answer 1

getElementsByTagName("segment_list")调用将获取所有segment_list元素（对于当前road_section），您必须将第二个内部循环限制为一次迭代而不是j < listaSegmentos.getLength()或者根本不使用循环并执行以下操作：

if(listaSegmentos.getLength()>=1) {
    Node nodeseg = listaSegmentos.item(0);
    if (nodeseg.getNodeType() == Node.ELEMENT_NODE) {
        Element el = (Element) nodeseg;
        System.out.println("\nSegment id : " + el.getAttribute("id"));
        System.out.println("height : " + el.getElementsByTagName("height").item(0).getTextContent().replaceAll("\"", ""));
        System.out.println("number_vehicles : " + el.getElementsByTagName("number_vehicles").item(0).getTextContent().trim());
    }
}

同样适用于第一个内部循环，其条件设置为i < 1

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1 个答案: