code: private CompilerType getDefaultCompiler() {
          try {
              final String prop = this.conf.getChainedProperties().getProperty( JAVA_COMPILER_PROPERTY,
                                                                                "ECLIPSE" );
              if ( prop.equals( "NATIVE" ) ) {
                  return CompilerType.NATIVE;
              } else if ( prop.equals( "ECLIPSE" ) ) {
                  return CompilerType.ECLIPSE;
              } else if ( prop.equals( "JANINO" ) ) {
                  return CompilerType.JANINO;
              } else {
                  logger.error( "Drools config: unable to use the drools.compiler property. Using default. It was set to:" + prop );
                  return CompilerType.ECLIPSE;
              }
          } catch ( final SecurityException e ) {
              logger.error( "Drools config: unable to read the drools.compiler property. Using default.", e);
              return CompilerType.ECLIPSE;
          }
      }
docs: This will attempt to read the System property to work out what default to set.
  This should only be done once when the class is loaded. After that point, you will have
  to programmatically override it.