从配置文件中取得初始化参数

            <servlet>
                 <servlet-name>SearchItemServlet</servlet-name>
                 <servlet-class>com.bjpowernode.drp.basedata.web.SearchItemServlet</servlet-class>
                  <!-- 初始化参数的设置 -->
                 <init-param>
                     <param-name>page-size</param-name>
                     <param-value>3</param-value>
                 </init-param>
             </servlet>
             <servlet-mapping>
                 <servlet-name>SearchItemServlet</servlet-name>
                 <url-pattern>/servlet/item/SearchItemServlet</url-pattern>
             </servlet-mapping>

            <!-- 配置键值对，全局对象，所有的都能访问到 -->
            <context-param>
                <param-name>page-size</param-name>
                <param-value>3</param-value>
            </context-param>

            //从application范围内取得page-size,application指的是ServletContext对象
            int pageSize=Integer.parseInt(this.getServletContext().getInitParameter("page-seze"));