The important method in this class is passTest which will decide if we include a fieldMap or excluded it.

MyClassMapBuilder.java

public static class MyClassMapBuilder<A,B> extends ClassMapBuilder<A,B> {
		protected MyClassMapBuilder(Type<A> aType, Type<B> bType,
				MapperFactory mapperFactory,
				PropertyResolverStrategy propertyResolver,
				DefaultFieldMapper[] defaults) {
			super(aType, bType, mapperFactory, propertyResolver, defaults);
		}

		/* (non-Javadoc)
		 * @see ma.glasnost.orika.metadata.ClassMapBuilder#addFieldMap(ma.glasnost.orika.metadata.FieldMap)
		 */
		@Override
		protected void addFieldMap(FieldMap fieldMap) {
			if(passTest(fieldMap))
			    super.addFieldMap(fieldMap);
		}

		protected boolean passTest(FieldMap fieldMap) {
			if(fieldMap.getDestination().getType().isAssignableFrom(String.class) && !fieldMap.getSource().getType().isAssignableFrom(String.class))
				return false;
			return true;
		}



		public static class Factory extends ClassMapBuilder.Factory {

			/* (non-Javadoc)
			 * @see ma.glasnost.orika.metadata.ClassMapBuilder.Factory#newClassMapBuilder(ma.glasnost.orika.metadata.Type, ma.glasnost.orika.metadata.Type, ma.glasnost.orika.MapperFactory, ma.glasnost.orika.property.PropertyResolverStrategy, ma.glasnost.orika.DefaultFieldMapper[])
			 */
			@Override
			protected <A, B> ClassMapBuilder<A, B> newClassMapBuilder(
					Type<A> aType, Type<B> bType, MapperFactory mapperFactory,
					PropertyResolverStrategy propertyResolver,
					DefaultFieldMapper[] defaults) {
				return new MyClassMapBuilder<A,B>(aType, bType, mapperFactory, propertyResolver,
						defaults);
			}
			
		}
	}

Here is how to configure Orika to use it :

factoryBuilder.classMapBuilderFactory(new MyClassMapBuilder.Factory());