📄 +
字号:
this.work=work;<br>
<br>
others.add("挖坑");</p>
<p> others.add("钉木板");<br>
}</p>
<p> public void insert(){</p>
newMethod();<br>
}
<p><br>
<br>
//在新方法中,我们在insert之前增加其他方法,这里次序先后是用户灵活指定的 <br>
public void newMethod()<br>
{<br>
otherMethod();<br>
work.insert();<br>
<br>
<br>
} <br>
</p>
<p> public void otherMethod()<br>
{<br>
ListIterator listIterator = others.listIterator();<br>
while (listIterator.hasNext())<br>
{<br>
System.out.println(((String)(listIterator.next())) + "
正在进行");<br>
}<br>
<br>
} <br>
</p>
<p>}<br>
</p>
</td>
</tr>
</table>
<p>在上例中,我们把挖坑和钉木板都排在了打桩insert前面,这里只是举例说明额外功能次序可以任意安排.</p>
<p>好了,Decorator模式出来了,我们看如何调用:</p>
<p> Work squarePeg = new SquarePeg(); <br>
Work decorator = new Decorator(squarePeg);<br>
decorator.insert(); </p>
<p></p>
<p>Decorator模式至此完成.</p>
<p>如果你细心,会发现,上面调用类似我们读取文件时的调用:</p>
<p>FileReader fr = new FileReader(filename);<br>
BufferedReader br = new BufferedReader(fr);</p>
<p>实际上Java 的I/O API就是使用<a href="http://www-900.ibm.com/developerWorks/java/l-jdkdp/part3/index.shtml#2" target="_blank">Decorator实现的</a>,I/O变种很多,如果都采取继承方法,将会产生很多子类,显然相当繁琐.</p>
<p><b>Jive中的Decorator实现</b><br>
在论坛系统中,有些特别的字是不能出现在论坛中如"打倒XXX",我们需要过滤这些"反动"的字体.不让他们出现或者高亮度显示.</p>
<p>在IBM Java专栏中专门<a href="http://www-900.ibm.com/developerWorks/java/l-jivesrc/index.shtml#5" target="_blank">谈Jive的文章</a>中,有谈及Jive中ForumMessageFilter.java使用了Decorator模式,其实,该程序并没有真正使用Decorator,而是提示说:针对特别论坛可以设计额外增加的过滤功能,那么就可以重组ForumMessageFilter作为Decorator模式了.</p>
<p> 所以,我们在分辨是否真正是Decorator模式,以及会真正使用Decorator模式,一定要把握好Decorator模式的定义,以及其中参与的角色(Decoratee
和Decorator).</p>
<p> </p>
<p>设计模式如何在具体项目中应用见<a href="../mybook/index.htm" target="_blank">《Java实用系统开发指南》</a></p>
<p> </p>
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