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/></b></p>
<p><b><jsp:useBean id="nameobs" scope="session"
class="NameObserver" /><br>
<jsp:setProperty name="product" property="*"
/></b></p>
<p><b><jsp:useBean id="priceobs" scope="session"
class="PriceObserver" /><br>
<jsp:setProperty name="product" property="*"
/></b></p>
<p><%<br>
<br>
if (request.getParameter("save")!=null)<br>
{ <br>
product.saveToDb();<br>
<br>
<br>
out.println("产品数据变动 保存! 并已经自动通知客户"); </p>
<p>}else{<br>
<br>
//加入观察者<br>
product.addObserver(<b>nameobs</b>);<br>
<br>
product.addObserver(<b>priceobs</b>);</p>
<p>%></p>
<p> //request.getRequestURI()是产生本jsp的程序名,就是自己调用自己<br>
<form action="<%=request.getRequestURI()%>"
method=post></p>
<p> <input type=hidden name="save" value="1"><br>
产品名称:<input type=text name="name" ><br>
产品价格:<input type=text name="price"><br>
<input type=submit></p>
<p> </form></p>
<p><%<br>
<br>
} </p>
<p>%></p>
<p> </p>
<p> </p>
<p> </p>
</td>
</tr>
</table>
<p>执行改Jsp程序,会出现一个表单录入界面, 需要输入产品名称 产品价格, 点按Submit后,还是执行该jsp的<br>
if (request.getParameter("save")!=null)之间的代码.<br>
<br>
<br>
由于这里使用了数据javabeans的自动赋值概念,实际程序自动执行了setName setPrice语句.你会在服务器控制台中发现下面信息::<br>
<b><br>
NameObserver :name changet to ?????(Jsp表单中输入的产品名称)<br>
<br>
PriceObserver :price changet to ???(Jsp表单中输入的产品价格);</b></p>
<p>这说明观察者已经在行动了.!!<br>
同时你会在执行jsp的浏览器端得到信息:<br>
<br>
<b>产品数据变动 保存! 并已经自动通知客户</b> <br>
<br>
</p>
<p>上文由于使用jsp概念,隐含很多自动动作,现将调用观察者的Java代码写如下:</p>
<table width="80%" border="0" cellspacing="3" cellpadding="3" bgcolor="#CCCCCC">
<tr>
<td>
<p> </p>
<p>public class Test {</p>
<p> public static void main(String args[]){</p>
<p> Product product=new Product();<br>
<br>
NameObserver nameobs=new NameObserver();<br>
PriceObserver priceobs=new PriceObserver();</p>
<p>//加入观察者<br>
product.addObserver(nameobs);<br>
product.addObserver(priceobs);</p>
<p>product.setName("橘子红了");<br>
product.setPrice(9.22f); </p>
<p> }</p>
<p>}</p>
<p> </p>
<p> </p>
<p> </p>
</td>
</tr>
</table>
<p>你会在发现下面信息::<br>
<b><br>
NameObserver :name changet to 橘子红了<br>
<br>
PriceObserver :price changet to 9.22</b></p>
<p>这说明观察者在行动了.!!</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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