#2715: Updated documentation to reflect impact of conditions on update mappers. (#2740)

* #2715: added an example with an update mapper for Conditional behavior.

documentation/src/main/asciidoc/chapter-10-advanced-mapping-options.asciidoc

@@ -354,6 +354,56 @@ public class CarMapperImpl implements CarMapper {
 ----
 ====
 
+When using this in combination with an update mapping method it will replace the `null-check` there, for example:
+
+.Update mapper using custom condition check method
+====
+[source, java, linenums]
+[subs="verbatim,attributes"]
+----
+@Mapper
+public interface CarMapper {
+
+    CarDto carToCarDto(Car car, @MappingTarget CarDto carDto);
+
+    @Condition
+    default boolean isNotEmpty(String value) {
+        return value != null && !value.isEmpty();
+    }
+}
+----
+====
+
+The generated update mapper will look like:
+
+.Custom condition check in generated implementation
+====
+[source, java, linenums]
+[subs="verbatim,attributes"]
+----
+// GENERATED CODE
+public class CarMapperImpl implements CarMapper {
+
+    @Override
+    public CarDto carToCarDto(Car car, CarDto carDto) {
+        if ( car == null ) {
+            return carDto;
+        }
+
+        if ( isNotEmpty( car.getOwner() ) ) {
+            carDto.setOwner( car.getOwner() );
+        } else {
+            carDto.setOwner( null );
+        }
+
+        // Mapping of other properties
+
+        return carDto;
+    }
+}
+----
+====
+
 [IMPORTANT]
 ====
 If there is a custom `@Condition` method applicable for the property it will have a precedence over a presence check method in the bean itself.