These two items are very annoying when encountering this problem. Although they have no actual impact, programmers don’t like to see errors reported.
it’s generally good to make three changes

1. Change other versions to 3.0

<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="3.0"
 xmlns="http://java.sun.com/xml/ns/javaee"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <display-name>Archetype Created Web Application</display-name>
</web-app>

2. Find the root directory of the project, an XML in the. Setting file, or change the version to 3.0

<?xml version="1.0" encoding="UTF-8"?>
<faceted-project>
  <fixed facet="wst.jsdt.web"/>
  <installed facet="jst.web" version="3.0"/>
  <installed facet="wst.jsdt.web" version="1.0"/>
  <installed facet="java" version="1.8"/>
  <installed facet="jst.jaxrs" version="2.0"/>
  <installed facet="jst.jsf" version="2.2"/>
</faceted-project>

3. Another possibility is to see the directory missing and build path, and then create a new directory