SERVLET重要知识点

Servlet 基础
所有的servlet都是从HttpServlet继承而来的.
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>

过虑器
注意过虑器是双向过虑的.

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 来的时候");
  chain.doFilter(request, response);
  System.out.println("response 回来的时候");
 }

}

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的执行顺序严格按照web.xml里的配置顺序.
---------------
装饰模式
装饰者
被装饰者

分页

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

图形验证码



监听器
支持在ServletContext, HttpSession和ServletRequest对象变化时提供的通知.

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

注册时不分先后顺序

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

在web.xml中配置如下信息:

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

对不同的session应用不同的session
HttpSessionBindingListener