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摘要: java 设计模式之Observer
public class product extends Observable{
private String name;
private float price;
public String getName(){ return name;}
public void setName(){
this.name=name;
//设置变化点
setChanged();
notifyObservers(name);
}
public float getPrice(){ return price;}
public void setPrice(){
this.price=price;
//设置变化点
setChanged();
notifyObservers(new Float(price));
}
//以下可以是数据库更新 插入命令.
public void saveToDb(){
.....................
}
public class NameObserver implements Observer{
private String name=null;
public void update(Observable obj,Object arg){
if (arg instanceof String){
name=(String)arg;
//产品名称改变值在name中
System.out.println("NameObserver :name changet to "+name);
}
}
}
public class PriceObserver implements Observer{
private float price=0;
public void update(Observable obj,Object arg){
if (arg instanceof Float){
price=((Float)arg).floatValue();
System.out.println("PriceObserver :price changet to "+price);
}
}
}
<%
if (request.getParameter("save")!=null)
{
product.saveToDb();
out.println("产品数据变动 保存! 并已经自动通知客户");
}else{
//加入观察者
product.addObserver(nameobs);
product.addObserver(priceobs);
%>
//request.getRequestURI()是产生本jsp的程序名,就是自己调用自己
<form action="<%=request.getRequestURI()%>" method=post>
<input type=hidden name="save" value="1">
产品名称:<input type=text name="name" >
产品价格:<input type=text name="price">
<input type=submit>
</form>
<%
}
%>
public class Test {
public static void main(String args[]){
Product product=new Product();
NameObserver nameobs=new NameObserver();
PriceObserver priceobs=new PriceObserver();
//加入观察者
product.addObserver(nameobs);
product.addObserver(priceobs);
product.setName("橘子红了");
product.setPrice(9.22f);
}
}