mapstruct: generated implementation class doesn't seem okay

Question

I have the following mapstruct interface:

@Mapper
public interface CustomerMapper
{
  CustomerMapper INSTANCE = Mappers.getMapper(CustomerMapper.class);
  public Customer fromEntity(CustomerEntity customerEntity);
  @InheritInverseConfiguration
  CustomerEntity fromCustomer (Customer customer);
}

and here is the generated class:

public class CustomerMapperImpl implements CustomerMapper {
  public CustomerMapperImpl() {
  }

  public Customer fromEntity(CustomerEntity customerEntity) {
    if (customerEntity == null) {
      return null;
    } else {
      Customer customer = new Customer();
      return customer;
    }
  }

  public CustomerEntity fromCustomer(Customer customer) {
    if (customer == null) {
      return null;
    } else {
      CustomerEntity customerEntity = new CustomerEntity();
      return customerEntity;
    }
  }
}

Where are the setters ? The generated class is supposed to call the setters and to initialize properties, for example:

...
Customer customer = new Customer();
customer.setXXX(customerEntity.getXXX());
...

Here is the maven compile plugin configuration:

  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.5.1</version>
    <configuration>
      <source>11</source>
      <target>11</target>
      <annotationProcessorPaths>
        <path>
          <groupId>org.mapstruct</groupId>
          <artifactId>mapstruct-processor</artifactId>
          <version>${mapstruct.version}</version>
        </path>
        <path>
          <groupId>org.projectlombok</groupId>
          <artifactId>lombok</artifactId>
          <version>${lombock.version}</version>
        </path>
      </annotationProcessorPaths>
    </configuration>
  </plugin>

Did I miss anything here ?

Many thanks in advance.

Seymour