Java & xml学习笔记 SAX篇

1、需要软件

java,解析器(例如Xerces),API(例如SAX,DOM)

2、SAX机制

1)解析

String xmlURI = "c:/test.xml";

String vendorParserClass = "org.apache.xerces.parsers.SAXParser";

XMLReaer reader = XMLReaderFactory.createXMLReader(vendorParserClass);

InputSource inputSource = new InputSource(xmlURI);

reader.parse(inputSource);

这样一个xml文档解析过程就完成了。因为SAX是采用时间处理机制来解析XML

文档的，在解析过程中会触发一些事件，也就是执行特定的方法，你可以实现

这些方法，就可以通过解析xml来做一些事情了

2)处理

SAX2.0定义的核心处理接口一共有

org.xml.sax.ContentHandler

org.xml.sax.ErrorHandler

org.xml.sax.DTDHandler

org.xml.sax.EntityResolver

这些接口是通过

org.xml.sax.XMLReader的setContentHandler(),setEroorHandler(),

setDTDHandler(),setEntityHandler()注册到解析器，这里面最重要的是

org.xml.sax.ContentHandler接口，它具体如下

public interface ContentHandler{

public void setDocumentLocator(Locator locator);

public void startDocument() throws SAXException;

public void endDocument() throws SAXException;

public void startPrefixMapping(String prefix,String uri)

throws SAXException;

public void endPrefixMapping(String prifix)

throws SAXException;

public void startElement(String namespaceURI,String localName,

String qName,Attributes atts) throws SAXException;

public void endElement(String namespaceURI,String localName,

String qName) throws SAXException;

public void characters(char ch[],int start,int length)

throws SAXException;

public void ignorableWhitespace(char ch[],int start,int length)

throws SAXException;

public void processingInstruction(String target,String data)

throws SAXException;

public void skippedEntity(String name)

throws SAXException;

}

通过setContentHandler()将你实现的ContentHandler注册给XMLReader之后，

在解析过程中，系统根据各种条件执行接口中的方法，下面简单说明一下

1)文档定位器

private Locator locator;

public void setDocumentLocator(Locator locator){

this.locator = locator;

}

通常情况下，你只要如此实现就可以了，这个主要是得到当前解析的位置，

通过得到的locator，你可以使用它的getLineNumber(),getColumnName()等

方法，可以得到文档当前的位置，但要注意的是，这个locator不能保存，只

针对当前的解析有效

2)文档的开头和结尾

public void startDocument() throws SAXException{

//解析过程中仅位于setDocumentLocator()方法后调用

}

public void endDocument() throws SAXException{

//解析过程中最后调用

}

大多数情况下你可以不用理他们，只要写个空方法就可以了

3)名字空间的开始和结束

public void startPrefixMapping(String prefix,String uri)

throws SAXException{

}

public void endPrefixMapping(String prifix)

throws SAXException{

}

4)元素的开始和结束

public void startElement(String namespaceURI,String localName,

String qName,Attributes atts) throws SAXException{

}

public void endElement(String namespaceURI,String localName,

String qName) throws SAXException{

}

5)元素的数据

public void characters(char ch[],int start,int length)

throws SAXException{

String s = new String(ch,start,length);

}

这个是得到当前的元素的文本数据

6)可以忽略的空白

public void ignorableWhitespace(char ch[],int start,int length)

throws SAXException{

}

7)实体

public void skippedEntity(String name)

throws SAXException{

}

8)指令处理

public void processingInstruction(String target,String data)

throws SAXException{

}

3)例子：这个是从Java & XML 中复制过来的，

* Created on 2004-11-30

* TODO To change the template for this generated file go to

* Window - Preferences - Java - Code Style - Code Templates

package javaxml2;

/**

* @author yuangfang

* TODO To change the template for this generated type comment go to

* Window - Preferences - Java - Code Style - Code Templates

import java.io.*;

import java.util.*;

import org.xml.sax.*;

import org.xml.sax.ext.LexicalHandler;

import org.xml.sax.helpers.XMLReaderFactory;

import java.awt.*;

import javax.swing.*;

import javax.swing.tree.*;

public class SAXTreeViewer extends JFrame{

private String vendorParserClass = "org.apache.xerces.parsers.SAXParser";

private JTree jTree;

DefaultTreeModel defaultTreeModel;

public SAXTreeViewer(){

super("SAX Tree Viewer");

setSize(600,450);

}

public void init(String xmlURI) throws IOException,SAXException{

DefaultMutableTreeNode base = new DefaultMutableTreeNode("XML Document:" + xmlURI);

defaultTreeModel = new DefaultTreeModel(base);

jTree = new JTree(defaultTreeModel);

buildTree(defaultTreeModel,base,xmlURI);

getContentPane().add(new JScrollPane(jTree),BorderLayout.CENTER);

}

public void buildTree(DefaultTreeModel treeModel,DefaultMutableTreeNode base,String xmlURI)

throws IOException,SAXException{

String featureURI = "";

try{

XMLReader reader = XMLReaderFactory.createXMLReader(vendorParserClass);

ContentHandler jTreeContentHandler = new JTreeContentHandler(treeModel,base);

ErrorHandler jTreeErrorHandler = new JTreeErrorHandler();

reader.setContentHandler(jTreeContentHandler);

reader.setErrorHandler(jTreeErrorHandler);

reader.setEntityResolver(new SimpleEntityResolver());

featureURI = "http://xml.org/sax/features/validation";

reader.setFeature(featureURI,true);

featureURI = "http://xml.org/sax/features/namespaces";

setNamespaceProcessing(reader,true);

featureURI = "http://xml.org/sax/features/string-interning";

reader.setFeature(featureURI,true);

featureURI = "http://apache.org/xml/features/validation/schema";

reader.setFeature(featureURI,false);

InputSource inputSource = new InputSource(xmlURI);

reader.parse(inputSource);

}

catch(SAXNotRecognizedException e){

System.out.println("The parse class " + vendorParserClass

+ " does not recognize the feature URI " + featureURI);

System.exit(0);

}

catch(SAXNotSupportedException e){

System.out.println("The parser class " + vendorParserClass +

" does not support the feature URI " + featureURI);

}

private void setNamespaceProcessing(XMLReader reader,boolean state)

throws SAXNotSupportedException,SAXNotRecognizedException

{

reader.setFeature("http://xml.org/sax/features/namespaces",state);

reader.setFeature("http://xml.org/sax/features/namespace-prefixes",!state);

}

public static void main(String[] args) {

try{

if(args.length != 1){

System.out.println("Usage:Java javaxml2.SAXTreeViewer " + "[XML Document URI]");

System.exit(0);

}

SAXTreeViewer viewer = new SAXTreeViewer();

viewer.init(args[0]);

viewer.setVisible(true);

}catch(Exception e)

{

e.printStackTrace();

}

class JTreeContentHandler implements ContentHandler,LexicalHandler{

private DefaultTreeModel treeModel;

private DefaultMutableTreeNode current;

private Locator locator;

private Map namespaceMappings;

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#comment(char[], int, int)

public void comment(char[] ch, int start, int length) throws SAXException {

// TODO Auto-generated method stub

}

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#endCDATA()

public void endCDATA() throws SAXException {

// TODO Auto-generated method stub

}

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#endDTD()

public void endDTD() throws SAXException {

// TODO Auto-generated method stub

}

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#endEntity(java.lang.String)

public void endEntity(String name) throws SAXException {

// TODO Auto-generated method stub

current = (DefaultMutableTreeNode)current.getParent();

}

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#startCDATA()

public void startCDATA() throws SAXException {

// TODO Auto-generated method stub

}

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#startDTD(java.lang.String, java.lang.String, java.lang.String)

public void startDTD(String name, String publicId, String systemId)

throws SAXException {

// TODO Auto-generated method stub

System.out.println("start DTD");

DefaultMutableTreeNode dtdReference = new DefaultMutableTreeNode("DTD for '" + name + "'");

if(publicId != null)

{

DefaultMutableTreeNode publicIDNode = new DefaultMutableTreeNode("Public ID: " + publicId + "'");

dtdReference.add(publicIDNode);

}

if(systemId != null)

{

DefaultMutableTreeNode systemIDNode = new DefaultMutableTreeNode("System ID: " + systemId + "'");

dtdReference.add(systemIDNode);

}

current.add(dtdReference);

}

/* (non-Javadoc)

* @see org.xml.sax.ext.LexicalHandler#startEntity(java.lang.String)

public void startEntity(String name) throws SAXException {

// TODO Auto-generated method stub

DefaultMutableTreeNode entity = new DefaultMutableTreeNode("Entity: '" + name + "'");

current.add(entity);

current = entity;

}

public JTreeContentHandler(DefaultTreeModel treeModel,DefaultMutableTreeNode base)

{

this.treeModel = treeModel;

this.current = base;

this.namespaceMappings = new HashMap();

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#setDocumentLocator(org.xml.sax.Locator)

public void setDocumentLocator(Locator locator) {

// TODO Auto-generated method stub

this.locator = locator;

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#startDocument()

public void startDocument() throws SAXException {

// TODO Auto-generated method stub

System.out.println("start document");

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#endDocument()

public void endDocument() throws SAXException {

// TODO Auto-generated method stub

System.out.println("end document");

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#startPrefixMapping(java.lang.String, java.lang.String)

public void startPrefixMapping(String prefix, String uri) throws SAXException {

// TODO Auto-generated method stub

namespaceMappings.put(uri,prefix);

System.out.println("start PrefixMapping " + prefix);

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#endPrefixMapping(java.lang.String)

public void endPrefixMapping(String prefix) throws SAXException {

// TODO Auto-generated method stub

for(Iterator i = namespaceMappings.keySet().iterator();i.hasNext();)

{

String uri = (String) i.next();

String thisPrefix = (String)namespaceMappings.get(uri);

if(prefix.equals(thisPrefix)){

namespaceMappings.remove(uri);

break;

}

System.out.println("end PrefixMapping " + prefix);

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes)

public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {

// TODO Auto-generated method stub

DefaultMutableTreeNode element = new DefaultMutableTreeNode("Element: " + localName + " at line " + locator.getLineNumber());

current.add(element);

current = element;

if(uri.length() > 0)

{

String prefix = (String)namespaceMappings.get(uri);

if(prefix.equals("")){

prefix = "[None]";

}

DefaultMutableTreeNode namespace = new DefaultMutableTreeNode("Namespace: prefix = '" +

prefix + "',URI = '" + uri + "'");

current.add(namespace);

}

for(int i = 0;i<atts.getLength();i++)

{

DefaultMutableTreeNode attribute = new DefaultMutableTreeNode("Attribute (name = '" +

atts.getLocalName(i) + "',value = '" + atts.getValue(i) + "')");

String attURI = atts.getURI(i);

if(attURI.length() > 0)

{

String attPrefix = (String)namespaceMappings.get(attURI);

if(attPrefix.equals("")){

attPrefix = "[None]";

}

DefaultMutableTreeNode attNamespace = new DefaultMutableTreeNode("Namespace: prefix = '" +

attPrefix + "',URI = '" + attURI + "'");

attribute.add(attNamespace);

}

current.add(attribute);

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#endElement(java.lang.String, java.lang.String, java.lang.String)

public void endElement(String uri, String localName, String qName) throws SAXException {

// TODO Auto-generated method stub

current = (DefaultMutableTreeNode)current.getParent();

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#characters(char[], int, int)

public void characters(char[] ch, int start, int length) throws SAXException {

// TODO Auto-generated method stub

String s = new String(ch,start,length);

DefaultMutableTreeNode data = new DefaultMutableTreeNode("Character Data: '" + s + "'");

current.add(data);

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#ignorableWhitespace(char[], int, int)

public void ignorableWhitespace(char[] ch, int start, int length) throws SAXException {

// TODO Auto-generated method stub

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#processingInstruction(java.lang.String, java.lang.String)

public void processingInstruction(String target, String data) throws SAXException {

// TODO Auto-generated method stub

DefaultMutableTreeNode pi = new DefaultMutableTreeNode("PI (target = '"

+ target + "', data = '" + data + "')");

current.add(pi);

}

/* (non-Javadoc)

* @see org.xml.sax.ContentHandler#skippedEntity(java.lang.String)

public void skippedEntity(String name) throws SAXException {

// TODO Auto-generated method stub

DefaultMutableTreeNode skipped = new DefaultMutableTreeNode("Skipped Entity: '" + name + "'");

current.add(skipped);

}

class JTreeErrorHandler implements ErrorHandler{

/* (non-Javadoc)

* @see org.xml.sax.ErrorHandler#warning(org.xml.sax.SAXParseException)

public void warning(SAXParseException exception) throws SAXException {

// TODO Auto-generated method stub

System.out.println("**Parsing Warning**\n" +

" Line: " +

exception.getLineNumber() + "\n" +

" URI: " +

exception.getSystemId() + "\n" +

" Message:" +

exception.getMessage());

throw new SAXException("Warning encountered");

}

/* (non-Javadoc)

* @see org.xml.sax.ErrorHandler#error(org.xml.sax.SAXParseException)

public void error(SAXParseException exception) throws SAXException {

// TODO Auto-generated method stub

System.out.println("**Parsing Error**\n" +

" Line: " +

exception.getLineNumber() + "\n" +

" URI: " +

exception.getSystemId() + "\n" +

" Message:" +

exception.getMessage());

throw new SAXException("Error encounted");

}

/* (non-Javadoc)

* @see org.xml.sax.ErrorHandler#fatalError(org.xml.sax.SAXParseException)

public void fatalError(SAXParseException exception) throws SAXException {

// TODO Auto-generated method stub

System.out.println("**Parsing Fatal Error**\n" +

" Line: " +

exception.getLineNumber() + "\n" +

" URI: " +

exception.getSystemId() + "\n" +

" Message:" +

exception.getMessage());

throw new SAXException("Fatal Error encounted");

}

xml文件如下：你可以不用这个xml，用别的xml文件也可以

<?xml version="1.0"?>

<!DOCTYPE book SYSTEM "DTD/JavaXML.dtd">

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</chapter>

</contents>

<ora:copyright>&OReillyCopyright;</ora:copyright>

</book>

作者Blog：http://blog.csdn.net/flysyq/

Java &amp; xml学习笔记 SAX篇

Java & xml学习笔记 SAX篇