使用SAX和dom4j解析XML文档
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2022-05-29 11:50:19
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声明:类容为学习传智播客方立勋教学视频,总结。
一:SAX采用事件处理方式解析XML文档: 解析器 和 事件处理器(有多个处理器)
a:解析器可以使用JAXP的API创建,创建出SAX解析器后,就可以指定解析器去解析某个文档了。
b:解析器只要解析到xml文档的一个组成部分,就会调用时间处理器的一个方法,同时把当前解析到的内容作为方法的参数传递给事件处理器。
得到解析器是模版代码:
// 获取sax解析工厂
SAXParserFactory factory = SAXParserFactory.newInstance();
// 获取sax解析器
SAXParser sp = factory.newSAXParser();
// 获取sax读取器
XMLReader reader = sp.getXMLReader();
// 设置内容处理器
reader.setContentHandler(new TagValue());
// 读取xml内容
reader.parse("src/dom.xml");
我们的主要工作就是写事件处理器。
有两种方式:
a:实现ContentHandler接口
b:继承DefaultHandler类,覆盖我们需要的方法。
二:dom4j解析xml文档
二:dom4j解析xml文档
模版开始代码:
@Test
public void read() throws DocumentException{
SAXReader reader = new SAXReader();
Document doc = reader.read(new File("src/Book.xml"));
Element root = doc.getRootElement();
Element book = (Element) root.elements().get(1);
String value = book.element("书名").getText();
System.out.println(value);
}
写回文档的代码:
XMLWriter writer = new XMLWriter(new FileWriter("src/Book.xml"));
writer.write(doc);
writer.close();
dom4j有一个提取根标签的方法,很不错。
官方的说明文档很详细,基本一看就会了。就不在赘述了。
下面叙述一点XPath。w3cschool上面有这方面的讲解。但是讲解最好的个人认为是:http://zvon.org/xxl/XPathTutorial/General_chi/examples.html
实例:
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.junit.BeforeClass;
import org.junit.Test;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
/**
* sax解析xml文档
*
* @author forlab
* @version 2012-12-19
*/
public class Sax {
public static void main(String[] args) {
try {
ReadXml();
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@BeforeClass
public static void setUpBeforeClass() throws Exception {
}
public static void ReadXml() throws ParserConfigurationException, SAXException,
IOException {
// 获取sax解析工厂
SAXParserFactory factory = SAXParserFactory.newInstance();
// 获取sax解析器
SAXParser sp = factory.newSAXParser();
// 获取sax读取器
XMLReader reader = sp.getXMLReader();
// 设置内容处理器
BeanListHandler handler = new BeanListHandler();
reader.setContentHandler(handler);
// 读取xml内容
reader.parse("src/dom.xml");
List list = handler.getBooks();
}
}
class ListHander implements ContentHandler {
@Override
public void setDocumentLocator(Locator locator) {
// TODO Auto-generated method stub
}
@Override
public void startDocument() throws SAXException {
// TODO Auto-generated method stub
}
@Override
public void endDocument() throws SAXException {
// TODO Auto-generated method stub
}
@Override
public void startPrefixMapping(String prefix, String uri)
throws SAXException {
// TODO Auto-generated method stub
}
@Override
public void endPrefixMapping(String prefix) throws SAXException {
// TODO Auto-generated method stub
}
@Override
public void startElement(String uri, String localName, String qName,
Attributes atts) throws SAXException {
System.out.println("<"+qName+">");
//获取元素节点的属性值
for(int i=0;atts!=null && i<atts.getLength();i++){
String attName = atts.getQName(i);
String attValue = atts.getValue(i);
System.out.println(attName+"="+attValue);
}
}
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
System.out.println("<"+qName+">");
}
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
// TODO Auto-generated method stub
System.out.println(new String(ch, start, length));
}
@Override
public void ignorableWhitespace(char[] ch, int start, int length)
throws SAXException {
// TODO Auto-generated method stub
}
@Override
public void processingInstruction(String target, String data)
throws SAXException {
// TODO Auto-generated method stub
}
@Override
public void skippedEntity(String name) throws SAXException {
// TODO Auto-generated method stub
}
}
//继承类代码实现更容易
class TagValue extends DefaultHandler {
private String currentName;
private int needNum = 1;
private int currentNum;
@Override
public void startElement(String uri, String localName, String qName,
Attributes atts) throws SAXException {
// TODO Auto-generated method stub
currentName = qName;
if(currentName.equals("作者")){
currentNum++;
}
}
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
// TODO Auto-generated method stub
currentName = null;
}
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
// TODO Auto-generated method stub
if ("作者".equals(currentName) && currentNum == needNum ) {
System.out.println(new String(ch, start, length));
}
}
}
class BeanListHandler extends DefaultHandler{
private List list = new ArrayList();
private String currentTag;
private Book book;
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
currentTag = qName;
if("书".equals(currentTag)){
book = new Book();
}
}
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
if("书".equals(qName)){list.add(book);
book = null;
}
currentTag = null;
}
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
System.out.println("内容="+new String(ch,start,length));
if("书名".equals(currentTag)){
String value = new String(ch,start,length);
book.setName(value);
}
if("作者".equals(currentTag)){
String value = new String(ch,start,length);
book.setAuthor(value);
}
if("售价".equals(currentTag)){
String value = new String(ch,start,length);
book.setPrice(value);
}
}
public List getBooks(){
return list;
}
}
import java.io.File;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.BeforeClass;
import org.junit.Test;
/**
* @author forlab
* @version 2012-12-19
*/
public class Dom4j {
@BeforeClass
public static void setUpBeforeClass() throws Exception {
}
/**
* 利用xpath技术,查找dom.xml中name属性值为forlab的元素
* @throws DocumentException
*/
@Test
public void valid() throws DocumentException{
String username = "forlab";
SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/dom.xml"));
Node node = document.selectSingleNode("//作者[@name='"+username+"']");
if(node==null){
System.out.println("用户名或者密码错误!");
}else{
System.out.println("恭喜登陆成功!");
}
}
}
相关资料:http://www.blogjava.net/junglesong/archive/2008/02/21/181196.html