<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1" metadata-complete="true">
<display-name>Archetype Created Web Application</display-name>
</web-app>

 <build>
    <finalName>YMX</finalName>
    <plugins>
        <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-compiler-plugin</artifactId>
             <version>3.1</version>
             <configuration>
                 <source>1.8</source>     
                 <target>1.8</target>      
             </configuration>
       </plugin>
    </plugins>
  </build>

MAVEN --> update project

新建maven項目更改 web版本