1.打开项目所在目录下的.settings文件夹
打开org.eclipse.wst.common.project.facet.core.xml
把<installed facet="java" version="1.5"/>改成<installed facet="java" version="1.8"/>，把 <installed facet="jst.web" version="2.3"/>改成 <installed facet="jst.web" version="3.0"/>
<?xml version="1.0" encoding="UTF-8"?> <faceted-project> <fixed facet="wst.jsdt.web"/> <installed facet="java" version="1.8"/> <installed facet="jst.web" version="3.0"/> <installed facet="wst.jsdt.web" version="1.0"/> </faceted-project>
2.在pom.xml中增加
<!-- define the project compile level -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
解决maven项目Cannot change version of project facet Dynamic web module to 3.0/3.1
原文：https://www.cnblogs.com/achengmu/p/9101669.html