错误：The content of element type "web-app" must match "(icon?,display- name?,description?,distributable?,context-param*,filter*,filter-mapping*,listener*,servlet*,servlet- mapping*,session-config?,mime-mapping*,welcome-file-list?,error-page*,taglib*,resource-env- ref*,resource-ref*,security-constraint*,login-config?,security-role*,env-entry*,ejb-ref*,ejb-local-ref*)". - No grammar constraints (DTD or XML schema) detected for the document. web.xml头部配置： <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems,Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd"> <web-app> 原因：文档内容标签顺序不符合web-app_2_3.dtd规范 解决方案 1：严格按照提示上的顺序排列 2：删除<!DOCTYPE 。。。。这段内容
