<!--配置ServletContext_--><servlet><servlet-name>ServletContext_</servlet-name><servlet-class>com.li.servlet.servletcontext.ServletContext_</servlet-class></servlet><servlet-mapping><servlet-name>ServletContext_</servlet-name><url-pattern>/servletContext_</url-pattern></servlet-mapping><!--配置整个网站的信息--><context-param><param-name>website</param-name><param-value>http://www.lili.net</param-value></context-param><context-param><param-name>company</param-name><param-value>lili有限公司</param-value></context-param>ServletContext_：package com.li.servlet.servletcontext;import javax.servlet.*;import javax.servlet.http.*;import java.io.IOException;public class ServletContext_ extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获取web.xml的context-parameter//1.获取到ServletContext对象ServletContext servletContext = getServletContext();//2.获取websiteString website = servletContext.getInitParameter("website");String company = servletContext.getInitParameter("company");System.out.println("website= " + website);System.out.println("company= " + company);//3.获取项目的工程路径String contextPath = servletContext.getContextPath();System.out.println("项目路径= " + contextPath);// /servlet_demo//4.得到项目发布后真正的工作路径//这里的斜杠/表示我们的项目发布后的根路径 D:\IDEA-workspace\servlet_demo\out\artifacts\servlet_demo_war_explodedString realPath = servletContext.getRealPath("/");System.out.println("项目发布后的绝对路径= " + realPath);}}浏览器访问ServletContext_：
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后台输出：
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13.4.2应用实例2-简单的网站访问次数统计器需求：完成一个简单的网站访问次数统计器
不管使用什么浏览器，每访问一次Servlet，就增加1访问次数，在后台输出，并将结果返回给浏览器显示
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WebUtils.java:
package com.li.servlet.servletcontext;import javax.servlet.ServletContext;public class WebUtils {//该方法对访问网站的次数累加，同时返回次数public static Integer visitCount(ServletContext servletContext) {//从servletContext获取 visit_count 属性 k-vObject visit_count = servletContext.getAttribute("visit_count");//判断visit_count是否为空if (visit_count == null) {//说明是第1次访问网站servletContext.setAttribute("visit_count", 1);visit_count = 1;} else {//说明是第二次或之后访问//visit_count+1visit_count = Integer.parseInt(visit_count + "") + 1;//再将其放回servletContextservletContext.setAttribute("visit_count", visit_count);}return Integer.parseInt(visit_count + "");}}Servlet01.java:package com.li.servlet.servletcontext;import javax.servlet.*;import javax.servlet.http.*;import javax.servlet.annotation.*;import java.io.IOException;import java.io.PrintWriter;@WebServlet(urlPatterns = {"/Servlet01"})public class Servlet01 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获取到ServletContext对象ServletContext servletContext = getServletContext();Integer visit_count = WebUtils.visitCount(servletContext);//输出显示response.setContentType("text/html;charset=utf-8");PrintWriter writer = response.getWriter();writer.print("<h1>该网站被访问的次数是" + visit_count + "</h1>");writer.flush();writer.close();}}
经验总结扩展阅读
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