cvc-complex-type.2.4.a: Invalid content was found starting with element 'async-supported'. One of '{"http://java.sun.com/xml/ns/javaee":init-param}' is expected.

第一种方案：  将  "http://java.sun.com/xml/ns/javaee"  换为  "http://java.sun.com/xml/ns/j2ee"    

      错误，错误原因为   根元素<web-app>中的模式文件不对，javaee只支持单个的config，要换成 j2ee   经过测试，修改完还会报错。

    第二种方案：直接将   xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"  删除(或注释)   

    经测试，不再报错

cvc-complex-type.2.4.a: Invalid content was found starting with element 'async-supported'. One of '{"http://java.sun.com/xml/ns/javaee":init-param}' is expected.

原文：https://www.cnblogs.com/duanwandao/p/9974875.html