来自 application.properties 的 Mapstruct 值

Question

Is it possible to set a value from a field from the application.properties file?

I am looking for something like

    @Mapping(target="version", expression="${application.version}")
    StateDto stateToStateDto(State state);

where application.version=v1 is from the application.properties file.

Answer 1

As far as my knowledge goes, this is not possible. Mapstruct analyses the @Mapping annotation in compile time. And the annotation parameters require constants. So getting them from a file would not be possible.

You can always implement something in MapStruct that fulfills your needs. But I would go with a simple self-implemented mapper where you take the value from your version field in runtime from the environment.

Answer 2

Consider a "util service" like:

@Service
public class ConstantPropertyService {

  @Value("${application.version}"
  private String appVersion;

  // accessors, more properties/stuff..
}

Then you can define your Mapping like:

@Mapper(// ..., ...
   componentModel = "spring")
public abstract class MyMapper {

  @Autowired
  private ConstantPropertyService myService;

  @Mapping(target="version", expression="java(myService.getAppVersion())")
  StateDto stateToStateDto(State state);
  // ...
}

See also:

• Mapstruct - How can I inject a spring dependency in the Generated Mapper class
• Mapstruct Expressions

Answer 3

This is not possible through MapStruct. However, a feature could be raised that would support some custom expression language that would use Spring @Value and inject that.

eg

@Mapping(target="version", expression="springValue(${application.version})")
StateDto stateToStateDto(State state);

and then MapStruct will generate something like:

@Component
public class StateMapperImpl {

    @Value("${application.version}")
    private String version;


    // ...
}