SAX解析XML file
http://chris-freedream.iteye.com/blog/375772
1. SAX简述:
SAX全称Simple APIfor XML, 用于简单并快速的解析XML文件，是基于事件处理的模型，SUN定义了规范，常用的主要接口包括ContentHandler,ErrorHanlder, XMLReader, XMLFilter, Attributes, InputSource, Locator, 及不常用的EntityResolver, DTDHandler,LexicalHandler, DeclHandler等, UML静态类图如下:
, 也许读者会问，这么多接口都要去实现，并且，很多接口中的方法并不是所要的，那岂不是做无用功，放心，其中有一个DefaultHanlder已经适配了所有的重要的接口，你只需要继承DefaultHandler并重写你所想处理的方法即可，比如 startElement,endElement, charactors等。
其中Apache下的Xerces(http://sax.sourceforge.net/)对这些接口有个集体的实现.
2.SAX in practice
被解析的XML文件:
<?xmlversion="1.0" encoding="utf-8"?>
<books>
<bookpages="1000" price="$99">
<name>Thinkingin java</name>
<version>3.0</version>
</book>
<bookpages="800" price="$40">
<name>JUnitin Action</name>
<version>2.0</version>
</book>
<bookpages="900" price="$70">
<name>Lucenein Action</name>
<version>2.0</version>
</book>
</books>
解析代码如下：
package com.chris.sax.action;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
importorg.xml.sax.helpers.XMLReaderFactory;
public class XMLParser
{
//handlernormal info.
protected PrintStream output =
new PrintStream( new BufferedOutputStream( new FileOutputStream(java.io.FileDescriptor.out ), 128 ), true );
//handlererror info.
protected PrintStream error =
new PrintStream( new BufferedOutputStream( new FileOutputStream(java.io.FileDescriptor.err ), 128 ), true );
public void parserXMLFile(String fileName ) throws SAXException,IOException
{
XMLReader reader =XMLReaderFactory.createXMLReader();
reader.setContentHandler( newMyContentHandler() );
reader.setErrorHandler( new MyErrorHandler());
InputSource source = new InputSource( newFileInputStream( new File( fileName ) ) );
reader.parse(source);
}
classMyErrorHandler implements ErrorHandler
{
publicvoid error( SAXParseException exception ) throws SAXException
{
error.println(exception.getMessage() );
}
publicvoid fatalError( SAXParseException exception ) throws SAXException
{
error.println(exception.getMessage() );
}
publicvoid warning( SAXParseException exception ) throws SAXException
{
output.println(exception.getMessage() );
}
}
classMyContentHandler implements ContentHandler
{
publicvoid characters( char[] ch, int start, int length )
throwsSAXException
{
output.print(ch);
}
publicvoid endDocument() throws SAXException
{
}
publicvoid endElement( String uri, String localName, String name )
throwsSAXException
{
output.println("</"+localName+">");
}
publicvoid endPrefixMapping( String prefix ) throws SAXException
{
}
publicvoid ignorableWhitespace( char[] ch, int start, int length )
throwsSAXException
{
}
publicvoid processingInstruction( String target, String data )
throwsSAXException
{
}
publicvoid setDocumentLocator( Locator locator )
{
}
publicvoid skippedEntity( String name ) throws SAXException
{
}
publicvoid startDocument() throws SAXException
{
output.println("<xmlversion=\"1.0\" encoding=\"utf-8\"?>");
}
publicvoid startElement( String uri, String localName, String name,
Attributesatts ) throws SAXException
{
//uriis identifier of namespace
//name-->prefix:localName
output.print("<"+localName );
for(int i = 0; i < atts.getLength(); i++ )
{
StringattrName = atts.getLocalName( i );
StringattrValue = atts.getValue( i );
output.print("" + attrName + "=" + attrValue );
}
output.print(">");
}
publicvoid startPrefixMapping( String prefix, String uri )
throwsSAXException
{
}
}
publicstatic void main( String[] args ) throws Exception, IOException
{
XMLParserparser = new XMLParser();
parser.parserXMLFile("books.xml");
}
}
解析后的结果如下:
<xml version="1.0"encoding="utf-8"?>
<books>
<books>
<bookpages="1000" price="$99">
<name>Thinkingin java</name>
<version>3.0</version>
</book>
<bookpages="800" price="$40">
<name>JUnitin Action</name>
<version>2.0</version>
</book>
<bookpages="900" price="$70">
<name>Lucenein Action</name>
<version>2.0</version>
</book>
</books>
<books>
<bookpages="1000" price="$99">
<name>Thinkingin java</name>
<version>3.0</version>
</book>
<bookpages="800" price="$40">
<name>JUnitin Action</name>
<version>2.0</version>
</book>
<bookpages="900" price="$70">
<name>Lucenein Action</name>
<version>2.0</version>
</book>
</books>
这样就把XML文件大体输出到屏幕上来了， 但是你会发现，这些不是你真正想要的结果，甚至出现了乱码，原因就在于characters可能被多次调用，甚至次数不定，以下是个改进的版本
package com.chris.sax.action;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.List;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
importorg.xml.sax.helpers.XMLReaderFactory;
public class XMLParser
{
//handlernormal info.
protected PrintStream output =
new PrintStream( new BufferedOutputStream( new FileOutputStream(java.io.FileDescriptor.out ), 128 ), true );
//handlererror info.
protected PrintStream error =
new PrintStream( new BufferedOutputStream(new FileOutputStream( java.io.FileDescriptor.err ), 128 ), true );
public void parserXMLFile(String fileName ) throws SAXException,IOException
{
XMLReader reader =XMLReaderFactory.createXMLReader();
reader.setContentHandler( newMyContentHandler() );
reader.setErrorHandler( new MyErrorHandler());
InputSource source = new InputSource( newFileInputStream( new File( fileName ) ) );
reader.parse(source);
}
classMyErrorHandler implements ErrorHandler
{
publicvoid error( SAXParseException exception ) throws SAXException
{
error.println(exception.getMessage() );
}
publicvoid fatalError( SAXParseException exception ) throws SAXException
{
error.println(exception.getMessage() );
}
publicvoid warning( SAXParseException exception ) throws SAXException
{
output.println(exception.getMessage() );
}
}
classMyContentHandler implements ContentHandler
{
private StringBuffer buffer = new StringBuffer();
private String key;
publicvoid characters( char[] ch, int start, int length )
throwsSAXException
{
buffer.append(ch, start, length);
}
publicvoid endDocument() throws SAXException
{
}
publicvoid endElement( String uri, String localName, String name )
throwsSAXException
{
if(key.equals( localName))
{
output.print(buffer);
}
output.print("</"+localName+">");
}
publicvoid endPrefixMapping( String prefix ) throws SAXException
{
}
publicvoid ignorableWhitespace( char[] ch, int start, int length )
throwsSAXException
{
}
publicvoid processingInstruction( String target, String data )
throwsSAXException
{
}
publicvoid setDocumentLocator( Locator locator )
{
}
publicvoid skippedEntity( String name ) throws SAXException
{
}
publicvoid startDocument() throws SAXException
{
output.println("<xmlversion=\"1.0\" encoding=\"utf-8\"?>");
}
publicvoid startElement( String uri, String localName, String name,
Attributesatts ) throws SAXException
{
//uriis identifier of namespace
//name-->prefix:localName
buffer.delete(0,buffer.length());
key= localName;
output.print("<"+localName );
for(int i = 0; i < atts.getLength(); i++ )
{
StringattrName = atts.getLocalName( i );
StringattrValue = atts.getValue( i );
output.print("" + attrName + "=" + attrValue );
}
output.print(">");
}
publicvoid startPrefixMapping( String prefix, String uri )
throwsSAXException
{
}
}
publicstatic void main( String[] args ) throws Exception, IOException
{
XMLParserparser = new XMLParser();
parser.parserXMLFile("books.xml");
}
}
输出结果如下:
<xml version="1.0" encoding="utf-8"?>
<books><book pages=1000 price=$99><name>Thinking in java</name><version>3.0</version></book><book pages=800 price=$40><name>JUnit in Action</name><version>2.0</version></book><book pages=900 price=$70><name>Lucene in Action</name><version>2.0</version></book></books>
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