Servlet获取web.xml中的参数方法

<context-param>

<param-name>count</param-name>

<param-value>1200</param-value>

</context-param>

<servlet>

<description>loginServlet</description>

<display-name>loginServlet</display-name>

<servlet-name>loginServlet</servlet-name>

<servlet-class>loginServlet</servlet-class>

<init-param>

<description>系统初始化数</description>

<param-name>num</param-name>

<param-value>100</param-value>

</init-param>

</servlet>

<servlet-mapping>

<servlet-name>loginServlet</servlet-name>

<url-pattern>/loginServlet</url-pattern>

</servlet-mapping>

获取参数的方法以及异同

String username=request.getParameter("username");

response.setCharacterEncoding("gb2312");

System.out.println("getServletContext()："+getServletContext());

ServletContext context=getServletConfig().getServletContext();

String num=context.getInitParameter("num");//
<init-param> 获取不到值

String count=context.getInitParameter("count");//<context-param> 获取到值

System.out.println("num："+num);//null

System.out.println("count："+count);//1200

System.out.println("num："+getServletConfig().getInitParameter("num"));//100获取到值

System.out.println("count："+getServletConfig().getInitParameter("count"));//null获取不到值

System.out.println("request.getSession().getServletContext()："+request.getSession().getServletContext());

request.setAttribute("username", username);

PrintWriter out=response.getWriter();

out.println("获取的用户名是："+username);