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[英]How to get the first child node of the root element in xml using DOM parser?
[英]Cannot get first child of Xml Node
我的问题是使用getFirstChild()
获取XML
节点的第一个子节点。 我的xml很基础,如下:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<network name="beep">
<layers number="3">
<layer index="0" lenght="3">
...
</layer>
<layer index="1" lenght="3">
...
</layer>
....
</layers>
</network>
Java代码
import org.w3c.dom.*;
import javax.xml.parsers.*;
import java.io.StringReader;
import org.xml.sax.InputSource;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
try {
DocumentBuilderFactory DBF = DocumentBuilderFactory.newInstance();
DocumentBuilder DB = DBF.newDocumentBuilder();
Document doc = DB.parse(new InputSource( new StringReader(Xml)));
doc.getDocumentElement().normalize();
Element root = doc.getDocumentElement();
NodeList Nodes =root.getElementsByTagName("network");
Node Layers = Nodes.item(0).getFirstChild();
}
catch (Exception ex)
{
}
如您所见,有一个元素是“网络”的子元素,它是“层”。 我可以成功访问网络,获取节点列表,这基本上是一个节点,但是一旦我尝试获取第一个(也是唯一一个)节点的第一个子节点:
Node Layers = Nodes.item(0).getFirstChild();
我得到一个例外,更有趣的是,例外是null
。
问题出在哪里?
Please try below code(both Files):
1) XML File:
_________
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<network name="beep">
<layers number="3">
<layer index="0" lenght="3">Hare</layer>
<layer index="1" lenght="3">Rama</layer>
<layer index="0" lenght="3">Hare</layer>
<layer index="1" lenght="3">Krishna</layer>
</layers>
</network>
**************************************************************
2) Java File:
__________
import java.io.InputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
public class XMLDemo {
public static void main(String...lsdfs) {
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
try {
InputStream inputStream = XMLDemo.class.getClassLoader().getResourceAsStream("dataFilePackage/XmlData.xml");
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
Document document = documentBuilder.parse(inputStream);
NodeList nodeList = document.getElementsByTagName("network");
System.out.println(nodeList.item(0).getTextContent());
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}
我将您的 xml 修改为:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<network name="beep">
<layers number="3">
<layer index="0" lenght="3">Vishwa</layer>
<layer index="1" lenght="3">Ratna</layer>
</layers>
</network>
Java代码:
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class Main {
public static void main(String[] args) {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream inputStream = Main.class
.getClassLoader().getResourceAsStream("resources/nodes.xml");
Document doc = builder.parse(inputStream);
NodeList nodes = doc.getElementsByTagName("network");
System.out.println(nodes.item(0).getTextContent());
} catch (FileNotFoundException | ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
输出/输出
Vishwa
Ratna
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