What causes imported Maven project in Eclipse to use Java 1.5 instead of Java 1.6 by default and how can I ensure it doesn't?

Quick walk-through: "Java version supremacy battle"

Winner takes it all: maven-compiler-plugin

Start by ensuring the Maven Compiler uses Java 1.6, regardless of your IDE's preference for Java versioning. Right-click on your project, select Maven > Update Project Configuration, and refresh your project. This trick resolves any hiccups your m2eclipse might have in interpreting these settings.

Let's give Eclipse a voice: Project settings

Confirm that Eclipse's project build path mirrors the Java version noted in your pom.xml. If not, head to Project > Properties > Java Build Path > Libraries and manually switch the JRE System Library to Java 1.6. Remember, direct control can be a good thing! 😎

Party spoilers: Dependencies

Flick through your pom.xml once to ensure no dependencies are overriding your strict Java 1.6 instructions. Converge all Java version related settings in the <properties> section of your pom.xml. Doing so facilitates easier management and minimizes mis-configurations.

M2Eclipse plugin: The peace negotiator

For smooth sailing, assure that the m2eclipse plugin coexists peacefully with your Maven settings. Stumble upon frequent build errors? Beware! It could signal version mismatches. Keeping both the Maven plugins and m2eclipse updated will iron out any compatibility wrinkles.

Diversity welcome: Alternate JRE configuration

There might be a day when you want to run or compile using a different version of Java than the default selected by Eclipse. This is where the Alternate JRE setting in Eclipse swoops in. Use this feature to specify your preferred version.

Updates: The necessary evil

Maven plugins evolution is a reality, especially the maven-compiler-plugin. Keeping track of updates ensures compatibility with newer Java versions and ushers in fixes and enhancements that might affect Java version settings.

Note: "Updating might be a bummer, but stagnation is worse!" 😉

Hitchhiker's guide to Java version management

Battle after import: Eclipse or Maven?

After importing a Maven project into Eclipse, ensure Eclipse has not defaulted to its own Java preferences over Maven's. Following the trail at project's properties > Java Compiler section, check that the compiler compliance level is 1.6.

Conflict resolutions

Any imported project acting peculiar? Symptoms like failing to recognize certain Java 1.6 features (like @Override annotations) are usually indications of a version conflict. In this case, rejig the Eclipse JRE System Library and compiler settings to match the Maven pom.xml.

The big boss: Parent POM

Maven follows a hierarchical project structure, implying parent POMs could be the real puppet masters dictating Java versions. If mysteriously unresolved Java versioning issues persist, don't forget to snoop around the parent POM!