使用Proxool连接池， 当在重启Tomcat容器时，出现
Exception in Thread "HouseKeeper" java.lang.NullPointerException
空指针异常错误。
原因是：
This is because Proxool is not being shutdown properly. If the JVM stops then Proxool recognises that and shuts down gracefully, but if you redeploy Proxool into some environments (for example, a servlet container) then Proxool needs to be explicitly told so by calling ProxoolFacade.shutdown(). If you have a servlet container then you could put it in the servlet’s destroy() method. Alternatively, use the ServletConfigurator to both configure and shutdown Proxool
大概就是：
Proxool没正常关闭，要调用ProxoolFacade.shutdown().
解决办法：
随便写个Servlet，在Servlet的destroy()方法中显式地proxool关闭连接池：ProxoolFacade.shutdown();
public class ProxoolServlet extends HttpServlet {
public void init() throws ServletException {
}
public void destroy() {
ProxoolFacade.shutdown();
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
doGet(request,response);
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
}
}
然后将该Servlet配置到web.xml中：
<servlet>
<servlet-name>proxoolServlet </servlet-name>
<servlet-class>xxx.ProxoolServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
如果你用的是spring的话，还简单点，只要在spring的配置文件applicationContext.xml 增加
<bean id="dataSourceFacade" class="org.logicalcobwebs.proxool.ProxoolFacade" destroy-method="shutdown"/>
copy from：
http://hszdz.javaeye.com/blog/321156
http://yang7527.javaeye.com/blog/427512
