Java解析xml文档之SAX解析

sax解析是一种边读边解析，仅向前读取，不能修改，用来读。

sax创建XMLReader三步：

SAXParserFactory factory = SAXParserFactory.newInstance();
        SAXParser parser = factory.newSAXParser();
        XMLReader reader = parser.getXMLReader();

sax是使用类似于监听机制和适配器思想来做解析的，里面去覆盖方法：

reader.setContentHandler(new DefaultHandler(){}

具体实例代码如下：

sxaDemo

package cn.hncu.sax_stax;

import java.awt.Button;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.junit.Test;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

public class SaxDemo {
@Test //了解Sax解析的生命周期(工作流程)
public void SaxDemo1() throws Exception{
       SAXParserFactory factory = SAXParserFactory.newInstance();
       SAXParser parser = factory.newSAXParser();
        XMLReader reader=parser.getXMLReader();
        reader.setContentHandler( new DefaultHandler(){
@Override
public void startDocument() throws SAXException {
                System.out.println("1 开始读取文档了....");
            }
@Override
public void endDocument() throws SAXException {
                System.out.println("10 文档读取结束了....");
            }
@Override
public void startElement(String uri, String localName,
                    String qName, Attributes attributes) throws SAXException {
                System.out.println("一个元素开始....");
            }
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
                System.out.println("一个元素结束....");
            }
        });

        reader.parse("./xml5/users.xml");
        System.out.println("Over.....");
   }

//用SAX解析xml的基本套路
@Test 
public void SaxDemo2() throws Exception{
        SAXParserFactory factory = SAXParserFactory.newInstance();//1
        SAXParser parser = factory.newSAXParser();//2
        XMLReader reader = parser.getXMLReader();//3
        reader.setContentHandler(new DefaultHandler(){
//覆盖相应的事件处理方法---最核心的步骤※※※※
        });//4
        reader.parse("./xml5/users.xml");//5
    }


/*
 * 需求：输出xml文档的数据信息，格式如下：
 * id:A001
 name:Jack
 age:25
 ------------
 id:A002
 name:张三
 age:80
 -----------
 。。。。。
 */
private String elementName="@#";
@Test 
public void SaxDemo3() throws Exception{
        SAXParserFactory factory = SAXParserFactory.newInstance();//1
        SAXParser parser = factory.newSAXParser();//2
        XMLReader reader = parser.getXMLReader();//3
        reader.setContentHandler(new DefaultHandler(){

@Override
public void startElement(String uri, String localName,
                    String qName, Attributes attributes) throws SAXException {
if(qName.equals("user")){
                    String id = attributes.getValue("id");
                    System.out.println("id:"+id);
                }else if(qName.equals("name") || qName.equals("age")){
                    elementName = qName;
                }
            }

@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
if(qName.equals("name") || qName.equals("age")){
                    elementName ="@#";
                }else if(qName.equals("user")){
                    System.out.println("--------------");
                }
            }

//读取：xml文档中的“文本内容”---不包含属性和标签，但是含有空格和换行等空白符
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if(!elementName.equals("@#"))
                System.out.println(elementName+":"+new String(ch,start,length));
            }

        });//4
        reader.parse("./xml5/users.xml");//5
    }

}

users.xml

<?xml version="1.0" encoding="utf-8"?>

<users> 
<user id="A001"> 
<name>jack</name>  
<age>23</age> 
</user>  
<user id="b001"> 
<name>Mike</name>  
<age>25</age> 
</user> 
</users>