SAX解析XML文档——（二）

　　SAX从上向下解析，一行一行解析。节省内存，不适合CRUD。

XML文档:

<?xml version="1.0" encoding="UTF-8"?>
<书架>
    <书>
        <书名 name="xxxxx">Java高级</书名>
        <作者>武陟县</作者>
        <价格>200元</价格>
    </书>
    <书>
        <书名>Java中级</书名>
        <作者>打火机</作者>
        <价格>2000元</价格>
    </书>
</书架>

--------------------------------------------解析所有的内容:-----------------

 package XMLParse;

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

 import org.apache.commons.lang.Validate;
 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;

 public class Demo1 {

     public static void main(String[] args) throws Exception {
         // 1.创建解析工厂
         SAXParserFactory factory = SAXParserFactory.newInstance();
         // 2.得到解析器
         SAXParser sParser = factory.newSAXParser();
         // 3.得到读取器
         XMLReader reader = sParser.getXMLReader();
         // 4.设置内容处理器
         reader.setContentHandler(new ListHandler());
         // 5.读取xml文件
         reader.parse("src/Book.xml");
     }
 }

 // 得到xml文档的所有内容
 class ListHandler implements ContentHandler {

     // 处理开始标签
     @Override
     public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {
         System.out.println("<" + qName + ">");
 //        常用的循环方式      读取属性
         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);
         }
     }

     // 处理内容
     @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));
     }

     // 处理结束标签
     @Override
     public void endElement(String uri, String localName, String qName) throws SAXException {
         System.out.println("</" + qName + ">");

     }

     @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 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

     }

 }

结果:

<书架>

<书>

<书名>
name=xxxxx
Java高级
</书名>

<作者>
武陟县
</作者>

<价格>
200元
</价格>

</书>

<书>

<书名>
Java中级
</书名>

<作者>
打火机
</作者>

<价格>
2000元
</价格>

</书>

</书架>

 -----------------------------------------解析指定的标签------------------------------------------------------

 package XMLParse;

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

 import org.apache.commons.lang.Validate;
 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;

 public class Demo3 {

     public static void main(String[] args) throws Exception {
         // 1.创建解析工厂
         SAXParserFactory factory = SAXParserFactory.newInstance();
         // 2.得到解析器
         SAXParser sParser = factory.newSAXParser();
         // 3.得到读取器
         XMLReader reader = sParser.getXMLReader();
         // 4.设置内容处理器
         reader.setContentHandler(new TagValueHandler_1());
         // 5.读取xml文件
         reader.parse("src/Book.xml");
     }
 }

 //读取指定的标签（读取书名）
 class TagValueHandler_1 extends DefaultHandler{

     private String currentTag;  //记住当前的标签是那个
     private int needNum = 2;    //记住需要第几个
     private int currentNum;     //记住当前是第几个

     @Override
     public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
         if("书名".equals(qName)){
             currentTag="书名";
             currentNum++;
         }
     }

     @Override
     public void endElement(String uri, String localName, String qName) throws SAXException {
         currentTag=null;
     }

     @Override
     public void characters(char[] ch, int start, int length) throws SAXException {
         if("书名".equals(currentTag)&&needNum==currentNum){
             System.out.println(new String(ch,start,length));
         }
     }

 }

结果:

Java中级

-------------------------------------解析后封装到对象------------------------------

package XMLParse;

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.apache.commons.lang.Validate;
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;

public class Demo4 {

    public static void main(String[] args) throws Exception {
        // 1.创建解析工厂
        SAXParserFactory factory = SAXParserFactory.newInstance();
        // 2.得到解析器
        SAXParser sParser = factory.newSAXParser();
        // 3.得到读取器
        XMLReader reader = sParser.getXMLReader();
        // 4.设置内容处理器
        ListBeanHandler listBeanHandler = new ListBeanHandler();
        reader.setContentHandler(listBeanHandler);
        // 5.读取xml文件
        reader.parse("src/Book.xml");
        List<Book> list = listBeanHandler.getList();
        System.out.println(list);

    }
}

// 读取指定的标签（读取书名）
class ListBeanHandler extends DefaultHandler {

    private String currentTag; // 记住当前的标签是那个
    private List<Book> list = new ArrayList<Book>();
    private Book book;

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        currentTag = qName;
        if ("书".equals(qName)) {
            book = new Book();
        }
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        if("书名".equals(currentTag)){
            book.setName(new String(ch, start, length));
        }
        if("作者".equals(currentTag)){
            book.setAuthor(new String(ch, start, length));
        }
        if("价格".equals(currentTag)){
            book.setPrice(new String(ch, start, length));
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        currentTag = null;
        if("书".equals(qName)){
            list.add(book);
            book=null;
        }
    }

    public List<Book> getList() {
        return list;
    }

    public void setList(List<Book> list) {
        this.list = list;
    }

}

结果:

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