使用SAX解析XML实例根据属性查找

XML:

目的：输入sn=01 把相应的student的肮name和age取回

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="student.xsl"?>
<students>
  <student sn="01">
    <name>gao</name>
    <age>27</age>
  </student>
  <student sn="02">
    <name>yu</name>
    <age>24</age>
  </student>
</students>

package sax;

import java.io.File;
import java.io.IOException;
import java.util.Stack;

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

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class StudentLookup extends DefaultHandler {
    private String name;
    private String age;
    
    private String attrName;
    private String attrValue;
    
    private Stack tagsStack=new Stack();
    
    public void setAttrName(String attrName)
    {
        this.attrName = attrName;
    }

    public void setAttrValue(String attrValue)
    {
        this.attrValue = attrValue;
    }

    public void startElement(String uri, String localName, String qName, Attributes attrs) throws SAXException
    {
        
        if(tagsStack.empty())
        {
            
            if("student".equals(qName))
            {
                
                int len=attrs.getLength();
                for(int i=0;i<len;i++)
                {
                    
                    if(attrName.equals(attrs.getQName(i)) && 
                            attrValue.equals(attrs.getValue(i)))
                    {
                        tagsStack.push(qName);
                        break;
                    }
                }
            }
        }
        else
        {
            tagsStack.push(qName);
        }
    }
    
    public void characters(char[] ch, int start, int length) throws SAXException
    {

        if(!tagsStack.empty())
        {
            String tag=(String) tagsStack.peek();
            if("name".equals(tag))
                name=new String(ch,start,length);
            if("age".equals(tag))
                age=new String(ch,start,length);
        }
    }

    public void endElement(String uri, String localName, String qName) throws SAXException
    {
        if(!tagsStack.empty())
        {
            String tag=(String)tagsStack.pop();
            if(tagsStack.empty() && "student".equals(tag))
            {
                System.out.println("name: "+name);
                System.out.println("age: "+age);
                throw new SAXException("找到了匹配的学生");
            }
        }
    }

    public void endDocument() throws SAXException
    {
        System.out.println("没有找到匹配的学生");
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public Stack getTagsStack() {
        return tagsStack;
    }

    public void setTagsStack(Stack tagsStack) {
        this.tagsStack = tagsStack;
    }

    public String getAttrName() {
        return attrName;
    }

    public String getAttrValue() {
        return attrValue;
    }

    public static void main(String[] args) {
         if(args.length!=1){
             System.out.println("usage:java StudentLookup key=value");
             System.exit(0);
         }
         int index=args[0].indexOf("=");
         if(index==-1){
             System.out.println("usage:java StudentLookup key=value");
             System.exit(0);
         }
         String str=args[0].substring(0,index);
         StudentLookup sl=new StudentLookup();
         sl.setAttrName(str);
         
         String str1=args[0].substring(index+1);
         sl.setAttrValue(str1);
         
        
         String realpath=System.getProperty("user.dir")+File.separator+"src"+File.separator+"sax"+File.separator+"student.xml";    
           SAXParserFactory spf=SAXParserFactory.newInstance();
           try {
            SAXParser parser=spf.newSAXParser();
            parser.parse(new File(realpath), sl);
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {

            e.printStackTrace();
        }

    }



}

用异常完成查找，结果如下：

name: gao
age: 27
org.xml.sax.SAXException: 找到了匹配的学生
 at sax.StudentLookup.endElement(StudentLookup.java:84)
 at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
 at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
 at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
 at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
 at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
 at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
 at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
 at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
 at javax.xml.parsers.SAXParser.parse(SAXParser.java:375)
 at javax.xml.parsers.SAXParser.parse(SAXParser.java:311)
 at sax.StudentLookup.main(StudentLookup.java:148)

如果不想打印出异常堆栈，则只要屏蔽掉
catch (SAXException e) {
   e.printStackTrace();
}