4.13

package demo;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Enumeration;

public class Demo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletConfig servletConfig = getServletConfig();
        Enumeration<String> initParameterNames = servletConfig.getInitParameterNames();
        System.out.println(servletConfig.getServletName());
        while (initParameterNames.hasMoreElements()){
            String s = initParameterNames.nextElement();
            String initParameter = servletConfig.getInitParameter(s);
            System.out.println("value = " + initParameter + "  name = " + s);
        }
        ServletContext servletContext = servletConfig.getServletContext();
        Enumeration<String> initParameterNames1 = servletContext.getInitParameterNames();
        while (initParameterNames1.hasMoreElements()){
            String s = initParameterNames1.nextElement();
            String initParameter = servletContext.getInitParameter(s);
            System.out.println("value = " + initParameter + "  name = " + s);
        }
        String upload = servletContext.getRealPath("upload");
        System.out.println(upload);
        Integer count = (Integer) servletContext.getAttribute("count");
        if(count==null){
            count = 1;
            servletContext.setAttribute("count",count);
            System.out.println("count = " + count);
        }else {
            count++;
            System.out.println("count = " + count);
            servletContext.setAttribute("count",count);
        }
        System.out.println("demo01 doGet");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    
    
    <!--    -->
    <servlet>
        <servlet-name>Demo01</servlet-name>
        <servlet-class>demo.Demo01</servlet-class>
        <init-param>
            <param-name>name</param-name>
            <param-value>tom</param-value>
        </init-param>
        <init-param>
            <param-name>password</param-name>
            <param-value>1234</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>Demo01</servlet-name>
        <url-pattern>/demo01</url-pattern>
    </servlet-mapping>

    <context-param>
        <param-name>name</param-name>
        <param-value>jack</param-value>
    </context-param>
</web-app>