从任意数据结构生成XML解析器产生SAX事件

  • Z时代
  • 2024-01-10
  • 分类：IT

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();        }    }

    public void parse(String systemId) throws IOException, SAXException {    }

    public DTDHandler getDTDHandler() {        return null;    }

    public EntityResolver getEntityResolver() {        return null;    }

public ErrorHandler getErrorHandler() {        return null;    }

    public boolean getFeature(String name) throws SAXNotRecognizedException,            SAXNotSupportedException {        return false;    }

    public Object getProperty(String name) throws SAXNotRecognizedException,            SAXNotSupportedException {        return null;    }

    public void setContentHandler(ContentHandler handler) {        this.handler = handler;    }

    public void setDTDHandler(DTDHandler handler) {    }

    public void setEntityResolver(EntityResolver resolver) {    }

    public void setErrorHandler(ErrorHandler handler) {    }

    public void setFeature(String name, boolean value) throws            SAXNotRecognizedException, SAXNotSupportedException {    }

    public void setProperty(String name, Object value) throws            SAXNotRecognizedException, SAXNotSupportedException {    }

    void output(String name, String line) throws SAXException {        int tmp = name.length();        int startIndex=tmp+1;        int textLength = line.length() - startIndex;        String characters = line.substring(startIndex,line.length()-1);        handler.ignorableWhitespace(indent.toCharArray(), 0, // start index                                    indent.length());        handler.startElement(nsu, name, name /*"qName"*/, atts);

        handler.characters(characters.toCharArray(), startIndex, textLength);        handler.endElement(nsu, name, name);    }

}具体观察者对象: ConcreateObserver类package test;

import org.xml.sax.helpers.DefaultHandler;import org.xml.sax.*;public class ConcreateObserver extends DefaultHandler {    public ConcreateObserver() {    }

    public void startElement(String uri,                         String localName,                         String qName,                         Attributes attributes)                  throws SAXException{              System.out.println("startElement: "+localName);          }          public void characters(char[] ch,                                 int start,                                 int length)                throws SAXException{            System.out.println("characters: ");            System.out.print(ch);            System.out.println();        }}测试类:TestMain package test;import java.io.*;import org.xml.sax.InputSource;public class TestMain {    public TestMain() {    }

    public static void main(String[] args) throws Exception {        TestMain testmain = new TestMain();        FileReader in = new FileReader(new File("d:\\AddressBookReaderLog01.txt"));

        ConcreateObserver observer=new ConcreateObserver();        ParseXMLSubject parse = new ParseXMLSubject();        parse.setContentHandler(observer);

        parse.parse(new InputSource(in));    }}测试文本文档:AddressBookReaderLog01.txtAddressBookReader01 ../samples/PersonalAddressBook.ldifnickname: Fredemail: fred@barneys.househtml: TRUEfirstname: Fredlastname: Flintstonework: 999-Quarryhome: 999-BedrockLanefax: 888-Squawkpager: 777-pagercell: 555-cell

另外一个也比较也有意思的地方就是具体观察者类从DefaultHandler 继承,该类是缺省适配器模式的应用.

以上是 从任意数据结构生成XML解析器产生SAX事件 的全部内容， 来源链接： utcz.com/p/205191.html

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