Servlet 重要知識點

Servlet 基礎
全部的servlet都是從HttpServlet繼承而來的.
Servlet配置:在web.xml中

<servlet>
  <servlet-name>
  </servlet-name>
  <servlet-class>
  </servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>
  </servlet-name>
  <url-pattern>
  </url-pattern>
</servlet-mapping>

過慮器
注意過慮器是雙向過慮的.

public class Filter1 implements javax.servlet.Filter {

 public void init(FilterConfig config)
  throws ServletException() {

 }

 public void destory(){}

 public void doFilter(ServletRequest request,
        ServletResponse response,
        FilterChain chain)
  throws IOException, ServletException {
  System.out.println("request 來的時候");
  chain.doFilter(request, response);
  System.out.println("response 回來的時候");
 }

}

Filter配置信息:

<filter>
  <filter-name></filter-name>
  <filter-class></filter-class>
</filter>
<filter-mapping>
  <filter-name></filter-name>
  <url-pattern>*</url-pattern>
</filter-mapping>

Filter的執行順序嚴格按照web.xml裏的配置順序.
---------------
裝飾模式
裝飾者
被裝飾者

分頁

select top pageNo*pageSize * from bean
where beanId not in
(select top (pageNo-1).pageSize * from bean)

圖形驗證碼



監聽器
支持在ServletContext, HttpSession和ServletRequest對象變化時提供的通知.

<listener>
  <listener-class />
</listener>

註冊時不分前後順序

public class OnlineListener implements ServletContextListener {
  public void contextDestroyed(ServletContextEvent event) {
  }
  public void contextInitialized(ServletContextEvent event) {
      ServletContext application = event.getServletContext();
      // to do
  }
}

在web.xml中配置以下信息:

<listener>
  <listener-class>OnlineListener</listener-class>
</listener>

對不一樣的session應用不一樣的session HttpSessionBindingListener