假设已经配置好java，tomcat环境
创建AppListener.java文件
import java.util.HashMap; import java.util.Map; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; import javax.servlet.annotation.WebListener; @WebListener public class AppListener implements ServletContextListener { @Override public void contextDestroyed(ServletContextEvent sce) { } @Override public void contextInitialized(ServletContextEvent sce) { ServletContext servletContext = sce.getServletContext() ; Map<String, String> countries = new HashMap<String, String>(); countries.put("ca", "Canada"); countries.put("us", "United States"); servletContext.setAttribute("countries", countries); } }
编译将.class文件放于apache-tomcat-9.0.6(Tomcat安装目录)webappsROOTWEB-INFclasses下，在WEB-INFweb-xml中添加
<listener> <listener-class>AppListener</listener-class> </listener>
在<web-app> </web-app>标签内
创建countries.jsp文件
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> <html> <head> <title>Country List</title> </head> <body> We operate in these countries: <ul> <c:forEach items="${countries}" var="country"> <li>${country.value}</li> </c:forEach> </ul> </body> </html>
保存于ROOTjsp中（jsp文件夹自己添加）
添加jstl-1.2.jar和javax.servlet-api-4.0.1.jar到ROOTWEB-INFlib中
启动tomcat
浏览器输入http://localhost:8080/jsp/countries.jsp
可以看到
此方法只为过一把成功的瘾，具体原理和教程自行百度。