Java XML解析 - 使用SAX 示例

关键注意（SAX解析XML是基于事件模型的，即以消息机制的。）：

DefaultHandler类（org.xml.sax.helpers.DefaultHandler），java.io.CharArrayWriter类，javax.xml.parsers.SAXParserFactory类，javax.xml.parsers.SAXParser类

函数有：

public void startDocument() throws SAXException；

public void endDocument() throws SAXException；

public void startElement(String namesapaceURI, String localname, String qName, Attributes attr) throws SAXException；

public void endElement(String namespaceURI, String localName, String qName) throws SAXException；

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

分别是重写了CALLBACK方法：startDocument,endDocument,startElement,endElement,characters方法。

作用分别是当访问文档开始时、访问文档结束、访问元素开始、访问元素结束、遇到不能作为tag的字符串时候调用（即遇到类似<mytag>Hello,I am Alex!</mytag>中的"Hello,I am Alex!"时调用）。
另外注意：创建一个解析XML类的步骤，如何将自定义的类绑定为“DefaulHandler”（即saxParser.parse(new File("ticketRequest.xml"), trp);）。

实际上，以下程序虽然很简单，但确是SAX方法解析XML的基本框架。

//TicketReuqestParser.java

package myjaxp;

import myjaxp.TicketRequest2;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
import javax.xml.parsers.*;
import java.io.*;
public class TicketReuqestParser extends DefaultHandler
{
private CharArrayWriter buffer=new CharArrayWriter();
static TicketRequest2 tr2;
String custIDString;
String cruiseIDString;
public void startDocument() throws SAXException
{
System.out.println("startDocument() called");
}
public void endDocument() throws SAXException
{
System.out.println("endDocument() called");
}
public void startElement(String namesapaceURI, String localname, String qName, Attributes attr) throws SAXException
{

for (int i=0; i<attr.getLength(); i++)
{
String attrName=attr.getQName(i);
if (attrName.equals("custID"))
{
custIDString=attr.getValue(i);
}
if (attrName.equals("cruiseID"))
{
cruiseIDString=attr.getValue(i);
}
}
buffer.reset();
}
public void endElement(String namespaceURI, String localName, String qName) throws SAXException
{
//System.out.println("endElement called");
storeElement(qName);
}
public void characters(char[] ch,int start, int length) throws SAXException
{
buffer.write(ch,start,length);
}
private void storeElement(String elementName)
{
if (elementName.equals("ticketRequest"))
{

}
if (elementName.equals("customer"))
{
tr2.setCustID(Integer.parseInt(custIDString));
}
if (elementName.equals("firstName"))
{
tr2.setFirstName(buffer.toString());
}
if (elementName.equals("lastName"))
{
tr2.setLastName(buffer.toString());
}
if (elementName.equals("cruise")) {
tr2.setCruiseID(Integer.parseInt(cruiseIDString));
}
if (elementName.equals("destination"))
{
tr2.setDestination(buffer.toString());

}
if (elementName.equals("port"))
{
tr2.setPort(buffer.toString());
}
if (elementName.equals("sailing"))
{
tr2.setSailing(buffer.toString());
}
if (elementName.equals("numberOfTickets"))
{
String numberOfTicketString=buffer.toString();
int numberOfTickets;
if (!numberOfTicketString.equals(""))
{
numberOfTickets = Integer.parseInt(numberOfTicketString);

tr2.setNumberOfTickets(numberOfTickets);}
}
if (elementName.equals("isCommissionable"))
{
tr2.setCommissionable(true);
}

}
public String toString()
{
return tr2.toString();
}
public static void main(String[] args)
{
System.out.println("TicketRequestParser main()");
DefaultHandler trp=new TicketReuqestParser();
tr2=new TicketRequest2();
SAXParserFactory factory=SAXParserFactory.newInstance();
try
{
SAXParser saxParser=factory.newSAXParser();
saxParser.parse(new File("ticketRequest.xml"), trp);
}
catch(Exception e)
{
System.out.println("Exception in :"+e);
}
System.out.println(trp);
}

}
附：

/*
* TicketRequest2.java
*
* Created on January 19, 2002, 11:22 AM
*/

package myjaxp;

/**
*
* @author Stephen Potts
* @version
*/
public class TicketRequest2 implements java.io.Serializable
{
//information about the customer
int custID;
String lastName;
String firstName;

//information about the cruise
int cruiseID;
String destination;
String port;
String sailing;

int numberOfTickets;
boolean commissionable;
boolean approved;

public TicketRequest2()
{
}

/** Constructor */
public TicketRequest2(int custID, String lastName, String firstName,
int cruiseID, String destination,
String port, String sailing, int numberOfTickets,
boolean isCommissionable)
{
//set the information about the customer
this.custID = custID;
this.lastName = lastName;
this.firstName = firstName;

//set the information about the cruise
this.cruiseID = cruiseID;
this.destination = destination;
this.port = port;
this.sailing = sailing;

this.numberOfTickets = numberOfTickets;
this.commissionable = commissionable;
this.approved = false;
}

public int getCustID()
{
return this.custID = custID;
}

public String getLastName()
{
return this.lastName = lastName;
}

public String getFirstName()
{
return this.firstName = firstName;
}

public int getCruiseID()
{
return this.cruiseID;
}

public String getDestination()
{
return this.destination;
}

public String getPort()
{
return this.port;
}

public String getSailing()
{
return this.sailing;
}

public int getNumberOfTickets()
{
return this.numberOfTickets;
}

public boolean isCommissionable()
{
return this.commissionable;
}

public boolean isApproved()
{
return approved;
}

public void setCustID(int custID)
{
this.custID = custID;
}

public void setLastName(String lastName)
{
this.lastName = lastName;
}

public void setFirstName(String firstName)
{
this.firstName = firstName;
}

public void setCruiseID(int cruiseID)
{
this.cruiseID = cruiseID;
}

public void setDestination(String destination)
{
this.destination = destination;
}

public void setPort(String port)
{
this.port = port;
}

public void setSailing(String sailing)
{
this.sailing = sailing;
}

public void setNumberOfTickets(int numberOfTickets)
{
this.numberOfTickets = numberOfTickets;
}

public void setCommissionable(boolean commissionable)
{
this.commissionable = commissionable;
}

public void approve()
{
approved = true;
}

public void disApprove()
{
approved = false;
}

public String toString()
{
String outString;
outString = "-------------------------------------------" + "/n";

//information about the customer
outString += "custID = " + this.custID + "/n";
outString += "lastName = " + this.lastName + "/n";
outString += "firstName = " + this.firstName + "/n";
outString += "-----------------------------------------" + "/n";

//information about the cruise
outString += "cruiseID = " + this.cruiseID + "/n";
outString += "destination = " + this.destination + "/n";
outString += "port = " + this.port + "/n";
outString += "sailing = " + this.sailing + "/n";
outString += "numberOfTickets = " + this.numberOfTickets + "/n";

//information about the status
outString += "commissionable = " + this.commissionable + "/n";
outString += "approved? = " + this.approved + "/n";
outString += "-----------------------------------------" + "/n";
return outString;
}
}

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

ticketRequest.xml

<?xml version='1.0' encoding='utf-8' standalone='no' ?>
<!--This XML document represents a request for a cruise ticket-->

<!DOCTYPE ticketRequest SYSTEM "ticketRequest.dtd">

<ticketRequest>
<customer custID="10003" >
<lastName>Carter</lastName>
<firstName>Joseph</firstName>
</customer>
<cruise cruiseID="3004">
<destination>Hawaii</destination>
<port>Honolulu</port>
<sailing>7/7/2001</sailing>
<numberOfTickets>5</numberOfTickets>
<isCommissionable/>
</cruise>
</ticketRequest>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

ticketRequest.dtd

<!ELEMENT ticketRequest (customer, cruise)>
<!ELEMENT customer ( lastName, firstName)>
<!ATTLIST customer custID NMTOKEN #REQUIRED>
<!ELEMENT lastName (#PCDATA)>
<!ELEMENT firstName (#PCDATA)>
<!ELEMENT cruise (destination, port, sailing, numberOfTickets,isCommissionable?)>
<!ATTLIST cruise cruiseID NMTOKEN #REQUIRED>
<!ELEMENT destination (#PCDATA)>
<!ELEMENT port (#PCDATA)>
<!ELEMENT sailing (#PCDATA)>
<!ELEMENT numberOfTickets (#PCDATA)>
<!ELEMENT isCommissionable EMPTY>