从任意数据结构生成XML解析器产生SAX事件

来源：作者：出处：巧巧读书 2006-08-09 进入讨论组

在j2ee1.4标准教材里看到一个很有趣的例子,从任意数据结构生成XML解析器产生SAX事件.数据结构可以是文本文件,PDF格式文档等.关键是自己解析这些数据源.另外一个有意思的地方是观察者模式的应用.所以就粗糙的改了一下并完整到可以测试运行.观察者模式简略UML图:

具体实现被观察者对象ParseXMLSubject类:
package test;

import java.io.*;
import org.xml.sax.helpers.AttributesImpl;
import org.xml.sax.*;

public class ParseXMLSubject implements XMLReader {
ContentHandler handler;

    String nsu = "";
    Attributes atts = new AttributesImpl();
    String rootElement = "addressbook";
    String indent = "\n    ";

public ParseXMLSubject(){

}

    public ContentHandler getContentHandler() {
        return handler;
    }

    public void parse(InputSource input) throws IOException, SAXException {
        try {
            // Get an efficient reader for the file
            java.io.Reader r = input.getCharacterStream();
            BufferedReader br = new BufferedReader(r);

// Read the file and display it's contents.
String line = br.readLine();

            while (null != (line = br.readLine())) {
                if (line.startsWith("email:")) {
                    break;
                }
            }

            if (handler == null) {
                throw new SAXException("No content handler");
            }

            // Note:
            // We're ignoring setDocumentLocator(), as well
            handler.startDocument();
            handler.startElement(nsu, rootElement, rootElement, atts);

            output("email", line);
            line = br.readLine();
            output("html", line);
            line = br.readLine();
            output("firstname", line);
            line = br.readLine();
            output("lastname", line);
            line = br.readLine();
            output("work", line);
            line = br.readLine();
            output("home", line);
            line = br.readLine();
            output("fax", line);
            line = br.readLine();
            output("pager", line);
            line = br.readLine();
            output("cell", line);
            handler.ignorableWhitespace("\n".toCharArray(), 0, // start index
                                        1 // length
                    );
            handler.endElement(nsu, rootElement, rootElement);
            handler.endDocument();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }