Maven: generics are not supported in -source 1.3

Today I was integrating two projects, and encountered a very intriguing bug whenever i try to compile and run the Maven project using either Eclipse's "Maven Build" or maven's "mvn clean compile" commands. Initially i was using maven2 and the bug complained that "maven-compiler-plugin" plugin not found in the POM file. I upgraded to maven 3.13. The original error message disappeared, but i got some new error messages:

[ERROR] (use -source 5 or higher to enable for-each loops)
[ERROR] /.../PAClassifierJsonDecoder.java:[53,7] error: generics are not supported in -source 1.3
[ERROR]
[ERROR] (use -source 5 or higher to enable generics)
[ERROR] /.../drools/RulesEngineActions.java:[112,37] error: generics are not supported in -source 1.3
[ERROR]
[ERROR] (use -source 5 or higher to enable generics)
[ERROR] /.../KafkaSpout.java:[3,7] error: static import declarations are not supported in -source 1.3
[ERROR]
[ERROR] (use -source 5 or higher to enable static import declarations)
[ERROR] /.../KafkaSpout.java:[53,29] error: generics are not supported in -source 1.3
[ERROR]
[ERROR] (use -source 5 or higher to enable generics)
[ERROR] /.../KafkaSpout.java:[193,5] error: annotations are not supported in -source 1.3
[ERROR]

After some googling, it appears that maven by default configured to have source set as 1.3 (on Ubuntu at least), so if the project has use anotation such as "@Override" or generic, it will complain as these are not supported on Java 1.3. The remedy is to include the "maven-compiler-plugin" plugin. This is intriguing as i looked through the merged project's POM, and it already has included the "maven-compiler-plugin" plugin in the build section, which should have worked.

After a more detailed scrutiny and compare with examples on the web, it was noticed that the "maven-compiler-plugin" written in the POM file has one additional line "<groupId>org.apache.maven</groupId>" as follows:

<plugin>
   <groupId>org.apache.maven</groupId>
   <artifactId>maven-compiler-plugin</artifactId>
   <version>3.1</version>
   <configuration>
      <source>1.7</source>
      <target>1.7</target>
   </configuration>
</plugin>       

Therefore i decided to remove the line "<groupId>org.apache.maven</groupId>". and it work this time after rerunning the maven command