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);
    }
}