private ELEngine getELEngine() {
        if (elEngine == null) {
            if (ELExpressionFactory.isSupported()) {
                if (RuntimeUtils.isOSGi()) {
                    ClassLoader classLoader = getClass().getClassLoader();
                    return new TcclELEngine(ELExpressionFactory.newInstance(classLoader), classLoader);
                } else {
                    return new DefaultELEngine(ELExpressionFactory.newInstance());
                }
            } else {
                return new NoopELEngine();
            }
        } else {
            return elEngine;
        }
    }
Creates an instance of {@link Mapper}. Mapper is configured according to the current builder state.
<p>
Subsequent calls of this method will return new instances.

@return new instance of {@link Mapper}.
core/src/main/java/com/github/dozermapper/core/DozerBeanMapperBuilder.java