Java DOM xml 无法获取子项
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/6444597/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Java DOM xml cant get child
提问by Raptrex
My XML looks like this:
我的 XML 看起来像这样：
<ConnProf ConnProfID="1111">
<ConnNum>1</ConnNum>
<IsMSPA>false</IsMSPA>
<IsArray>false</IsArray>
<IsDDOR>false</IsDDOR>
<Subsystem SSID="2222"ConnProfID="3333">
<SSName>AA</SSName>
<GenericSSName>AA</GenericSSName>
<ConnFuncAddr>aaa</ConnFuncAddr>
<DSSNum>22</DSSNum>
<isRemoved>false</isRemoved>
</Subsystem>
<Subsystem SSID="4444" ConnProfID="5555">
<SSName>BBBB</SSName>
<GenericSSName>BB</GenericSSName>
<ConnFuncAddr>bbbbbb</ConnFuncAddr>
<DSSNum>44</DSSNum>
<isRemoved>false</isRemoved>
</Subsystem>
I am having trouble getting ConnNum, IsMSPA, IsArray, and IsDDOR. I tried getting ConnNum with:
我在获取 ConnNum、IsMSPA、IsArray 和 IsDDOR 时遇到问题。我尝试使用以下方法获取 ConnNum：
//get ConnNum
Node n = doc.getFirstChild();
if (n.hasChildNodes())
System.out.println(n.getFirstChild().getNodeValue());
else
System.out.println(n.getNodeValue());
but it just returns null when im expecting 1.
但是当我期待 1 时它只返回 null。
import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class test
{
public static void main(String[] args)
{
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try
{
DocumentBuilder db = dbf.newDocumentBuilder();
for (int i = 1; i <= 8; i++)
{
Document doc = db.parse("file" + i + ".xml");
doc.getDocumentElement ().normalize ();
System.out.println ("Root element of the doc is " + doc.getDocumentElement().getNodeName());
//get ConnNum
Node n = doc.getFirstChild();
if (n.hasChildNodes())
System.out.println(n.getFirstChild().getNodeValue());
else
System.out.println(n.getNodeValue());
NodeList listOfSubsystems = doc.getElementsByTagName("Subsystem");
int totalSubsystems = listOfSubsystems.getLength();
if (totalSubsystems == 0)
continue;
else
{
System.out.println("Total number of subsystems : " + totalSubsystems + "\n");
Dish dish = new Dish();
for(int s=0; s < listOfSubsystems.getLength() ; s++)
{
Node firstPersonNode = listOfSubsystems.item(s);
if(firstPersonNode.getNodeType() == Node.ELEMENT_NODE)
{
Element firstPersonElement = (Element)firstPersonNode;
printElement(firstPersonElement, "SSName");
printElement(firstPersonElement, "GenericSSName");
printElement(firstPersonElement, "ConnFuncAddr");
printElement(firstPersonElement, "DSSNum");
printElement(firstPersonElement, "SCNum");
printElement(firstPersonElement, "SCAcronym");
printElement(firstPersonElement, "PassNum");
printElement(firstPersonElement, "FzCode");
printElement(firstPersonElement, "isRemoved");
System.out.println("------------------");
}
}
System.out.println("\n==============================");
}
}
}
catch(ParserConfigurationException pce)
{
pce.printStackTrace();
}
catch(SAXException se)
{
se.printStackTrace();
}
catch(IOException ioe)
{
ioe.printStackTrace();
}
}
public static void printElement(Element a, String name)
{
NodeList elementList = a.getElementsByTagName(name);
Element b = (Element)elementList.item(0);
if (b != null)
{
NodeList list = b.getChildNodes();
System.out.println( ((Node)list.item(0)).getNodeValue().trim() );
}
}
}
回答by andyb
Perhaps the first child is not what you think it is. Whitespaceis important in XML and it is possible that the firstChild is actually a textnode.
也许第一个孩子不是你想的那样。空格在 XML 中很重要，而且 firstChild 可能实际上是一个文本节点。
Nodeshave a type and you can iterate all the children checking for Elementnode type to get a handle to the actual elements.
节点有一个类型，您可以迭代所有子节点，检查元素节点类型以获取实际元素的句柄。
Edit:This prints the values you are after. It is filtering on Elementnodes and then the first child node (the one containing the text) of each.
编辑：这将打印您所追求的值。它过滤元素节点，然后过滤每个节点的第一个子节点（包含文本的节点）。
NodeList nodeList = n.getChildNodes();
for (int j = 0; j < nodeList.getLength(); j++) {
Node childNode = nodeList.item(j);
if (childNode.getNodeType() == Node.ELEMENT_NODE) {
System.out.println(childNode.getNodeName() + " " + childNode.getFirstChild().getNodeValue());
}
}
Also, as @Steve Townsend correctly writes, you could use getTextContent()instead of childNode.getFirstChild().getNodeValue()if you are using Java 1.5 or above.
此外，正如@Steve Townsend 所写的getTextContent()那样，childNode.getFirstChild().getNodeValue()如果您使用的是 Java 1.5 或更高版本，则可以使用代替。
回答by iKushal
NodeList nodeList = n.getChildNodes();
for (int j = 0; j < nodeList.getLength(); j++) {
Node childNode = nodeList.item(j);
if (childNode instanceof Element) {
Element childElement = (Element) childNode;
System.out.println(childElement.getNodeName() + " " + childElement.getFirstChild().getNodeValue());
}
}
回答by Steve Townsend
You need to use getTextContent()here. You can use getNodeName()first (in debug version only) to ensure you are in the correct place.
您需要在此处使用getTextContent()。您可以getNodeName()先使用（仅在调试版本中）以确保您处于正确的位置。
getNodeValue()returns nullif the node in hand is an element. There's a table herethat describes the results of getNode*in each possible context.
getNodeValue()null如果手中的节点是一个元素，则返回。有一个表在这里描述的结果，getNode*在每一个可能的方面。
回答by Triton Man
Try calling
试试打电话
doc.getDocumentElement()
instead of
代替
doc.getFirstChild()
回答by kingAm
If i am going to use DOM parser. I will always prefer following approach as we don't need to know every tag of xml and print them one by one.
如果我要使用 DOM 解析器。我将始终更喜欢以下方法，因为我们不需要知道 xml 的每个标签并一一打印它们。
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class RecDOMP {
public static void main(String[] args) throws Exception{
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setValidating(false);
DocumentBuilder db = dbf.newDocumentBuilder();
// replace following path with your input xml path
Document doc = db.parse(new FileInputStream(new File ("D:\ambuj\input.xml")));
// replace following path with your output xml path
File OutputDOM = new File("D:\ambuj\outapip1.txt");
FileOutputStream fostream = new FileOutputStream(OutputDOM);
OutputStreamWriter oswriter = new OutputStreamWriter (fostream);
BufferedWriter bwriter = new BufferedWriter(oswriter);
// if file doesnt exists, then create it
if (!OutputDOM.exists()) {
OutputDOM.createNewFile();}
visitRecursively(doc,bwriter);
bwriter.close(); oswriter.close(); fostream.close();
System.out.println("Done");
}
public static void visitRecursively(Node node, BufferedWriter bw) throws IOException{
// get all child nodes
NodeList list = node.getChildNodes();
for (int i=0; i<list.getLength(); i++) {
// get child node
Node childNode = list.item(i);
if (childNode.getNodeType() == Node.TEXT_NODE)
{
//System.out.println("Found Node: " + childNode.getNodeName()
// + " - with value: " + childNode.getNodeValue()+" Node type:"+childNode.getNodeType());
String nodeValue= childNode.getNodeValue();
nodeValue=nodeValue.replace("\n","").replaceAll("\s","");
if (!nodeValue.isEmpty())
{
System.out.println(nodeValue);
bw.write(nodeValue);
bw.newLine();
}
}
visitRecursively(childNode,bw);
}
}
}
