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

Assuming that you are using the m2e plugin in Eclipse, you‘ll need to specify the source and targetversions as 1.6 for maven-compiler-plugin. m2e uses these values to determine the project‘s Java compiler level. A snippet of the POM is shown below:

<build>
  <plugins>
    <plugin>
      <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>1.6</source>
          <target>1.6</target>
        </configuration>
    </plugin>
  </plugins>
</build>

Alternatively, you can specify the maven.compiler.source and maven.compiler.targetproperties with values of 1.6, that happen to be the equivalent:

<properties>
    <maven.compiler.target>1.6</maven.compiler.target>
    <maven.compiler.source>1.6</maven.compiler.source>
</properties>

 http://stackoverflow.com/questions/7715260/java-compiler-level-does-not-match-the-version-of-the-installed-java-project-fac