xmlparser.java

《Java与模式》一书的源代码

package com.javapatterns.xmlproperties;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import org.xml.sax.*;

class XMLParser implements DocumentHandler
{
    private static final int IN_NOTHING = 0;
    private static final int IN_DOCUMENT = 1;
    private static final int IN_KEY = 2;
    private int state = IN_NOTHING;

    private String key;
    private StringBuffer value;

    private Parser parser;
    private Class parserClass = null;
    private Properties xmlprop = null;

    public static final String PARSER_P = "org.apache.xerces.parsers.SAXParser";

    private Class getParserClass() throws ClassNotFoundException
    {
        if (parserClass == null)
        {
            parserClass = Class.forName(PARSER_P);
        }
        return parserClass;
    }

    private Parser getParser()
    {
        try
        {
            return (Parser)getParserClass().newInstance();
        }
        catch (Exception ex)
        {
            throw new RuntimeException("Unable to intantiate : " + PARSER_P);
        }
    }

    XMLParser(InputStream in, XMLProperties xmlprop) throws IOException, SAXException
    {
        this.xmlprop = xmlprop;

        state = IN_NOTHING;
        value = new StringBuffer();
        try
        {
            parser = getParser();
            parser.setDocumentHandler(this);
            parser.parse(new InputSource(in));
        }
        catch (Exception e)
        {
            e.printStackTrace();
            throw new SAXException("can't create parser ");
        }
    }

    public void startElement(String name, AttributeList atts) throws SAXException
    {
        if (state == IN_NOTHING)
        {
            if (name.equals("properties"))
            {
                state = IN_DOCUMENT;
            }
            else
            {
                throw new SAXException("attempt to find root properties");
            }
        }
        else if (state == IN_DOCUMENT)
        {
            if (name.equals("key"))
            {
                state = IN_KEY;
                key = atts.getValue("name");

                if (key == null)
                {
                    throw new SAXException("no name for key " + atts);
                }
            }
            else
            {
                throw new SAXException("attempt to find keys");
            }
        }
        else
        {
            throw new SAXException("invalid element " + name);
        }
    }

    public void endElement(String name) throws SAXException
    {
        if (state == IN_KEY)
        {
            xmlprop.setProperty(key, value.toString());

            System.out.print("<key name=\"" + key + "\">");
            System.out.println(value.toString() + "</key>\n");

            state = IN_DOCUMENT;

            value = new StringBuffer();
        }
        else if (state == IN_DOCUMENT)
        {
            state = IN_NOTHING;
        }
    }

    public void characters(char[] ch, int start, int length)
    throws SAXException
    {
        if (state == IN_KEY)
        {
            compute(ch, start, length);
        }
    }

    public void ignorableWhitespace(char[] ch, int start, int length)
    throws SAXException
    {
        // nothing to do
    }

    public void startDocument() throws SAXException
    {
        // nothing to do
    }

    public void endDocument() throws SAXException
    {
        // nothing to do
    }

    public void processingInstruction(String target, String data)
    throws SAXException
    {
        // nothing to do
    }

    public void setDocumentLocator(Locator locator)
    {
        // nothing to do
    }

    private void compute(char[] ch, int start, int length)
    {
        int st = start;
        int len = length - 1;
        while (st < length
        && ((ch[st] == '\n') || (ch[st] == '\t') || (ch[st] == ' ')
        || (ch[st] == '\r')))
        {
            st++;
        }
        while (len > 0
        && ((ch[len] == '\n')
        || (ch[len] == '\t')
        || (ch[len] == ' ')
        || (ch[len] == '\r')))
        {
            len--;
        }

        while (st <= len)
        {
            value.append(ch[st]);
            st++;
        }
    }
}