Dynamic Web Module 3.1 requires Java 1.7 or newer.

错误信息：Dynamic Web Module 3.1 requires Java 1.7 or newer.

Java compiler level does not match the version of the installed Java project facet.


解决办法：

在apache-maven-3.3.3\conf目录下settings文件中添加：
<profile>
<id>jdk-1.7</id>
<activation>
<activeByDefault>true</activeByDefault>
<jdk>1.7</jdk>
</activation>
<properties>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
<maven.compiler.compilerVersion>1.7</maven.compiler.compilerVersion>
</properties>
</profile>