web.xml上下文初始化参数

1、在web.xml文件中配置上下文参数

 <!--<context-param>标签声明上下文初始化参数，  -->
   <!-- 上下文初始化的参数可以被应用程序用所有servlet共享 -->
   <context-param>
       <!-- 上下文参数可以像map一样使用 -->
       <param-name>One</param-name><!-- 参数名 -->
       <param-value>hello</param-value><!-- 参数值 -->
   </context-param>
   <context-param>
       <param-name>Two</param-name>
       <param-value>dyf</param-value>
   </context-param>

2、在servlet中获取上下文参数

 //@WebServlet(name="HelloServlet01",value="/Hello")
 @WebServlet(name="HelloServlet01",urlPatterns="/Hello")
 public class HelloServlet01 extends HttpServlet {
     private static final long serialVersionUID = 1L;

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         this.doPost(request, response);

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         //创建一个获取上下文参数的对象
         ServletContext context = this.getServletContext();
         //获取上下文初始化的参数
         String initParameter = context.getInitParameter("One");
 //        context.getInitParameterNames();
         PrintWriter writer = response.getWriter();
         //将参数返回到页面
         writer.append(initParameter);
     }
 }