after using a page object
(e.g., the Result page object), Tapestry will not throw it away. Instead, it will put it into a pool for reuse (see the diagram
below). Later when it needs to use the Result page object again, it will check if the pool has one. If so, just take it out
from the pool and use it. Only when the pool has no such page object, will it create a new page object.
所以如果在一个新开的浏览器上面，页面上显示的参数不会发生改变，
防止这种情况的发生可以
在page-specification中加入
<property name="XXX"> XXX为页面上的变量
所以对应的页面为抽象的类 abstract，
对应的变量的get，set方法为abstract