saxtagcount.java

java编程入门配套光盘第八章代码

import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
import java.util.*;
import java.io.*;

public class SAXTagCount extends DefaultHandler 
{
    private Hashtable tagsList;
    // XML文件的开始
    public void startDocument() throws SAXException 
    {
        // 建立标记的Hashtable对象
        tagsList = new Hashtable();
    }
    // 元素的开始
    public void startElement(String namespaceURI, String localName,
                String qName, Attributes atts) throws SAXException 
    {
        String tagName = qName;
        int count;
        // 检查是否有此标记
        Object value = tagsList.get(tagName);
        if (value == null) 
        {
            // 不存在
            count = 1;
        } else {
            // 存在, 加一
            count = ((Integer)value).intValue();
            count++;
        }
        tagsList.put(tagName, new Integer(count));
    }
    // 元素的内容
    public void characters(String chars) throws SAXException 
    {
    }
    // 元素的结束
    public void endElement(String namespaceURI, String localName,
                String qName) throws SAXException 
    {
    }
    // 文件结束
    public void endDocument() throws SAXException 
    {
        Enumeration enum = tagsList.keys();
        while (enum.hasMoreElements()) 
        {
            String tagName = (String)enum.nextElement();
            // 获取计数
            int count = ((Integer)tagsList.get(tagName)).intValue();
            System.out.println(tagName + " (" + count + ")");
        }
    }
    // 将文件名转换成URL
    private static String convertToURL(String name) 
    {
        String path = new File(name).getAbsolutePath();
        if (File.separatorChar != '/') 
        {
            path = path.replace(File.separatorChar, '/');
        }
        if (!path.startsWith("/")) {
            path = "/" + path;
        }
        return "file:" + path;
    }
    
    static public void main(String[] args) 
    {
        String filename = null;
        boolean validation = false;  
        filename = "08_01.xml";
        
        SAXParserFactory spf = SAXParserFactory.newInstance();
        spf.setValidating(validation);
        
        XMLReader xmlReader = null;
        try {
            // 创建一个JAXP SAXParser
            SAXParser saxParser = spf.newSAXParser();
            
            // 得到封装的SAX XMLReader
            xmlReader = saxParser.getXMLReader();
        } catch (Exception ex) {
            System.err.println(ex);
            System.exit(1);
        }     
        // 设置XMLReader的ContentHandler
        xmlReader.setContentHandler(new SAXTagCount());
        // 在分析之前设置ErrorHandler
        xmlReader.setErrorHandler(new MyErrorHandler());
        try {
            // 告诉XMLReader分析XML文档
            xmlReader.parse(convertToURL(filename));
        } catch (SAXException se) {
            System.err.println(se.getMessage());
            System.exit(1);
        } catch (IOException ioe) {
            System.err.println(ioe);
            System.exit(1);
        }
    }  
    // 报告错误和警告
    private static class MyErrorHandler implements ErrorHandler 
    {
       //得到分析异常的细节
        private String getParseExceptionInfo(SAXParseException spe) 
        {
            String systemId = spe.getSystemId();
            if (systemId == null) {
                systemId = "null";
            }
            String info = "URI=" + systemId +
            " Line=" + spe.getLineNumber() +
            ": " + spe.getMessage();
            return info;
        }
        public void warning(SAXParseException spe) throws SAXException {
            System.out.println("Warning: " + getParseExceptionInfo(spe));
        }
        public void error(SAXParseException spe) throws SAXException {
            String message = "Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        }
        public void fatalError(SAXParseException spe) throws SAXException {
            String message = "Fatal Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        }
    }
}