How to create spring-based executable jar with maven?

You can add the following configuration so that the contents of the .schema files from all the jars get appended together.

<configuration>
  <transformers>
    <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
      <resource>META-INF/spring.handlers</resource>
    </transformer>
    <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
      <resource>META-INF/spring.schemas</resource>
    </transformer>
  </transformers>
</configuration>