JavaWeb-获取网站访问数量并且获得初始化参数

JavaWeb-获取网站访问数量并且获得初始化参数

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要点：

• 在web.xml设置初始化参数
• 如何获取初始化参数

• 重写init方法

  首先在web.xml设置初始化值

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"    id="WebApp_ID" version="3.0">    <context-param>                <param-name>count</param-name>        <param-value>1234</param-value>            </context-param>       <servlet>        <servlet-name>HitServlet</servlet-name>        <servlet-class>com.org.web.HitWebDemo</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>HitServlet</servlet-name>        <url-pattern>/Hit</url-pattern>    </servlet-mapping></web-app>

ServletContext对象包含在ServletConfig对象之中，ServletConfig对象在servlet初始化时提供servlet对象
getInitParameter()方法概述：public java.lang.String getInitParameter(java.lang.String name)
返回上下文定义的变量的值，如果变量不存在，返回null。

HitWebDemo.java

package com.org.web;import java.io.IOException;import java.io.PrintWriter;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;public class HitWebDemo extends HttpServlet {    private int count;    @Override    public void init(ServletConfig config) throws ServletException {        ServletContext servletContext = config.getServletContext();        count = Integer.parseInt(servletContext.getInitParameter("count")); // 获取初始化参数值    }    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        count++; // 访问的数量        resp.setContentType("text/html;charset=gb2312"); // 解决中文乱码问题        PrintWriter out = resp.getWriter();        out.println("<h3>您是第" + count + "位访客</h3>");        out.close();    }}