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<title>csdn_Factory模式和Abstract Factory模式</title>
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<TD WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" nowrap >Factory模式和Abstract Factory模式
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<p> <TD WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" nowrap >作者：jdeveloper</p>
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<font color="#FFAA00"> Java中的设计模式 (一) Factory模式和Abstract Factory模式 作者：jdeveloper </font>
Factory模式
利用给Factory对象传递不同的参数，以返回具有相同基类或实现了同一接口的对象。
Abstract Factory模式
先利用Factory模式返回Factory对象，在通过Factory对象返回不同的对象！
Java中的例子-----JAXP1.0.1 ：
以下是用Simple API for XML(SAX) Parse XML文件的片段
...
String uri = "file:" + new File (xmlfilename).getAbsolutePath ();
Parser parser;
<font color=red> //1. Abstract Factory模式
SAXParserFactory spf = SAXParserFactory.newInstance ();</font>
String validation = System.getProperty (
"javax.xml.parsers.validation", "false");
if (validation.equalsIgnoreCase("true"))
spf.setValidating (true);
<font color=red>//2. Factory模式
SAXParser sp = spf.newSAXParser ();</font>
parser = sp.getParser ();
parser.setDocumentHandler (this);
parser.parse (uri);
....
<font color=red>1.</font> SAXParserFactory中的静态方法newInstance()根据系统属性javax.xml.parsers.SAXParserFactory不同的值
生成不同的SAXParserFactory对象spf。然后SAXParserFactory对象又利用方法newSAXParser（）生成SAXParser对象。
注意：
SAXParserFactory 的定义为：
public abstract class SAXParserFactory extends java.lang.Object
SAXParserFactoryImpl 的定义为：
public class SAXParserFactoryImpl extends javax.xml.parsers.SAXParserFactory
public static SAXParserFactory newInstance() {
String factoryImplName = null;
try {
factoryImplName =
System.getProperty("javax.xml.parsers.SAXParserFactory",
"com.sun.xml.parser.SAXParserFactoryImpl");
}catch (SecurityException se) {
factoryImplName = "com.sun.xml.parser.SAXParserFactoryImpl";
}
SAXParserFactory factoryImpl;
try {
Class clazz = Class.forName(factoryImplName);
factoryImpl = (SAXParserFactory)clazz.newInstance();
}catch (ClassNotFoundException cnfe) {
throw new FactoryConfigurationError(cnfe);
} catch (IllegalAccessException iae) {
throw new FactoryConfigurationError(iae);
} catch (InstantiationException ie) {
throw new FactoryConfigurationError(ie);
}
return factoryImpl;
}
<font color=red>2.</font> newSAXParser（）方法在SAXParserFactory定义为抽象方法，
SAXParserFactoryImpl继承了SAXParserFactory，它实现了方法newSAXParser（）：
public SAXParser newSAXParser() throws SAXException,
ParserConfigurationException
{
SAXParserImpl saxParserImpl = new SAXParserImpl (this);
return saxParserImpl;
}
注意：
SAXParserImpl的定义为：
public class SAXParserImpl extends javax.xml.parsers.SAXParser
SAXParserImpl的构造函数定义为：
SAXParserImpl (SAXParserFactory spf) throws SAXException,
ParserConfigurationException
{
super();
this.spf = spf;
if (spf.isValidating ()) {
parser = new ValidatingParser();
validating = true;
}
else {
parser = new Parser();
}
if (spf.isNamespaceAware ()) {
namespaceAware = true;
throw new ParserConfigurationException
("Namespace not supported by SAXParser");
}
}
本例子中用到的class和interface的类关系图如下
<img src="factory.bmp" >
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