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?

Question

I imported a Maven project and it used Java 1.5 even though I have 1.6 configured as my Eclipse default Preferences->Java->Installed JREs.

When I

Answer 1

One more possible reason if you are using Tycho and Maven to build bundles, that you have wrong execution environment (Bundle-RequiredExecutionEnvironment) in the manifest file (manifest.mf) defined. For example:

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Engine Plug-in
Bundle-SymbolicName: com.foo.bar
Bundle-Version: 4.6.5.qualifier
Bundle-Activator: com.foo.bar.Activator
Bundle-Vendor: Foobar Technologies Ltd.
Require-Bundle: org.eclipse.core.runtime,
 org.jdom;bundle-version="1.0.0",
 org.apache.commons.codec;bundle-version="1.3.0",
 bcprov-ext;bundle-version="1.47.0"
Bundle-RequiredExecutionEnvironment: JavaSE-1.5
Export-Package: ...
...
Import-Package: ...
...

In my case everything else was ok. The compiler plugins (normal maven and tycho as well) were set correctly, still m2 generated old compliance level because of the manifest. I thought I share the experience.