How To Read XML File In Java – (DOM Parser)

本教程，将展现使用 DOM XML 解析技术，读取 XML 文件

DOM 解析器，将解析整个 XML 文档并且将把所有的 XML文档信息 加载到内存当中，然后再进行操作

简言之，此技术，将 XML 文件转换成 DOM 或者说是 树形结构，然后你就可以遍历结点了。

什么是节点？

在DOM中， XML文档 中的所有信息，都是节点。

例如：<salary>200000</salary>   salary是节点，200000也是节点，200000是文本节点。200000不是salary的值。

看定义：http://www.w3schools.com/dom/dom_nodes.asp  Text is Always Stored
in Text Nodes

警告（提示）：

DOM解析技术，速度慢，消耗很多内存.

对于大文件，通常使用 SAX技术，SAX 快速，消耗内存少。

1. DOM XML Parser Example

本例子，通过“name”获得节点，以及对应的值

D:\javaCode\staff.xml

<?xml version="1.0" encoding="UTF-8"?>
<company>
<staff id="1001">
<firstname>xiaohan</firstname>
<lastname>yi</lastname>
<nickname>xiaokai</nickname>
<salary>100000</salary>
</staff>
<staff id="2001">
<firstname>xiaowei</firstname>
<lastname>lan</lastname>
<nickname>xiaowei</nickname>
<salary>200000</salary>
</staff>
</company>

package com.domdemo;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;

public class ReadXMLFile {

public static void main(String argv[]) {

try {

File fXmlFile = new File("D:/javaCode/staff.xml");
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = documentBuilderFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);

// optional, but recommended
// read this -
// http://stackoverflow.com/questions/13786607/normalization-in-dom-parsing-with-java-how-does-it-work doc.getDocumentElement().normalize();
System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("staff");

System.out.println("-------------我是分隔线-------------------------------------------");

for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :" + nNode.getNodeName());

if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Staff id : "+ eElement.getAttribute("id"));
System.out.println("First Name : "+ eElement.getElementsByTagName("firstname").item(0).getTextContent());
System.out.println("Last Name : "+ eElement.getElementsByTagName("lastname").item(0).getTextContent());
System.out.println("Nick Name : "+ eElement.getElementsByTagName("nickname").item(0).getTextContent());
System.out.println("Salary : "+ eElement.getElementsByTagName("salary").item(0).getTextContent());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}

}

运行结果：

Root element :company
-------------我是分隔线-------------------------------------------

Current Element :staff
Staff id : 1001
First Name : xiaohan
Last Name : yi
Nick Name : xiaokai
Salary : 100000

Current Element :staff
Staff id : 2001
First Name : xiaowei
Last Name : lan
Nick Name : xiaowei
Salary : 200000
2. Looping the Node

本例子读取同样的“staff.xml“, 将展现如何一个接一个的循环节点，并且打印出节点名和值，如果有属性的话，也将属性打印出。

package com.domdemo;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class ReadXMLFileLoopNode {

public static void main(String[] args) {

try {

File file = new File("D:/javaCode/staff.xml");
DocumentBuilder dBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc = dBuilder.parse(file);
System.out.println("Root element :" + doc.getDocumentElement().getNodeName());

if (doc.hasChildNodes()) {
printNote(doc.getChildNodes());
}
} catch (Exception e) {
System.out.println(e.getMessage());
}

}

private static void printNote(NodeList nodeList) {
for (int count = 0; count < nodeList.getLength(); count++) {
Node tempNode = nodeList.item(count);
// make sure it's element node.
if (tempNode.getNodeType() == Node.ELEMENT_NODE) {
// 获取节点名，和节点值
System.out.println("\nNode Name =" + tempNode.getNodeName() + " [OPEN]");
System.out.println("Node Value =" + tempNode.getTextContent());

if (tempNode.hasAttributes()) {
// 获取属性名，和属性值
NamedNodeMap nodeMap = tempNode.getAttributes();

for (int i = 0; i < nodeMap.getLength(); i++) {
Node node = nodeMap.item(i);
System.out.println("attr name : " + node.getNodeName());
System.out.println("attr value : " + node.getNodeValue());
}

}

if (tempNode.hasChildNodes()) {
// loop again if has child nodes
printNote(tempNode.getChildNodes());
}
System.out.println("Node Name =" + tempNode.getNodeName() + " [CLOSE]");

}

}

}

}

Root element :company

Node Name =company [OPEN]
Node Value =

xiaohan
yi
xiaokai
100000

xiaowei
lan
xiaowei
200000

Node Name =staff [OPEN]
Node Value =
xiaohan
yi
xiaokai
100000

attr name : id
attr value : 1001

Node Name =firstname [OPEN]
Node Value =xiaohan
Node Name =firstname [CLOSE]

Node Name =lastname [OPEN]
Node Value =yi
Node Name =lastname [CLOSE]

Node Name =nickname [OPEN]
Node Value =xiaokai
Node Name =nickname [CLOSE]

Node Name =salary [OPEN]
Node Value =100000
Node Name =salary [CLOSE]
Node Name =staff [CLOSE]

Node Name =staff [OPEN]
Node Value =
xiaowei
lan
xiaowei
200000

attr name : id
attr value : 2001

Node Name =firstname [OPEN]
Node Value =xiaowei
Node Name =firstname [CLOSE]

Node Name =lastname [OPEN]
Node Value =lan
Node Name =lastname [CLOSE]

Node Name =nickname [OPEN]
Node Value =xiaowei
Node Name =nickname [CLOSE]

Node Name =salary [OPEN]
Node Value =200000
Node Name =salary [CLOSE]
Node Name =staff [CLOSE]
Node Name =company [CLOSE]

参考文献：

http://www.mkyong.com/java/how-to-read-xml-file-in-java-dom-parser/