MapStruct does not always use builders in target-object

[mfriess2]

Hi,

we try to use MapStruct with Lombok builders but MapStruct does not always seem to recognize and use the builders. Our particular problematic case is when the target object has a field which only has a builder.

Used MapStruct version: 1.3.1.FINAL
Used Lombok version: 1.18.10

It would be very helpful for us if you could let us know if this is considered a bug or not.
Looking forward to your feedback!

Here is an example:

Source POJO:

package example.model.source;

import lombok.Builder;
import lombok.Data;

@Data
@Builder
public class Car {
	private String model;
}

Target POJOs:

package example.model.target;

import lombok.Builder;
import lombok.Data;

@Data
@Builder
public class CarInsurance {
	private CarDetail carDetail;   // this is the problematic case
}

@Data
@Builder
public class CarDetail {
	private String model;
}

Mapper:

package example.mapper;

import example.model.source.Car;
import example.model.target.CarInsurance;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.MappingTarget;

@Mapper
public interface CarInsuranceMapper {
	@Mapping(source = "model", target = "carDetail.model")
	void map(Car source, @MappingTarget CarInsurance target);
}

MapStruct generates this mapper:

package example.mapper;

import example.model.source.Car;
import example.model.target.CarDetail;
import example.model.target.CarInsurance;
import javax.annotation.Generated;
import org.springframework.stereotype.Component;

@Generated(
    value = "org.mapstruct.ap.MappingProcessor"
)
@Component
public class CarInsuranceMapperImpl implements CarInsuranceMapper {

    @Override
    public void map(Car source, CarInsurance target) {
        if ( source == null ) {
            return;
        }

        if ( target.getCarDetail() == null ) {
            target.setCarDetail( new CarDetail() );  // THIS CREATES A COMPILE ERROR
        }
        carToCarDetail( source, target.getCarDetail() );
    }

    protected void carToCarDetail(Car car, CarDetail mappingTarget) {
        if ( car == null ) {
            return;
        }

        mappingTarget.setModel( car.getModel() );
    }
}

And the compiler fails with:

CarInsuranceMapperImpl.java:22: error: constructor CarDetail in class CarDetail cannot be applied to given types;
            target.setCarDetail( new CarDetail() );

It would work if MapStruct would generate:

if ( target.getCarDetail() == null ) {
    target.setCarDetail( CarDetail.builder().build() );
}

The annotation processor ordering in the Gradle build:

	implementation 'org.mapstruct:mapstruct'
	implementation 'org.projectlombok:lombok'
	annotationProcessor 'org.mapstruct:mapstruct-processor'
	annotationProcessor 'org.projectlombok:lombok'

[filiphr]

@mfriess2 I think that this is the same as #1581 and is caused by projectlombok/lombok#1538.

[mfriess2]

Thanks for taking the time to answer but I'm also a bit sad that you closed this issue so fast.

1 ) I am using the proposed solution from #1581 : lombok is after mapstruct (written in the gradle file; I think at execution time it is run reversed: first lombok then mapstruct)

To be double-sure, I tried out:

annotationProcessor 'org.mapstruct:mapstruct-processor', 'org.projectlombok:lombok'

similar to your example https://github.com/mapstruct/mapstruct-examples/blob/master/mapstruct-lombok/build.gradle (but I am using the newer "annotationProcessor" instead of "apt")

2 ) but most important: I de-lomboked the class "CarDetail" just to take Lombok out of the equation and the problem stays the same: the builder is not recognized/used by mapstruct and an uncompilable Mapper is generated

Here is the non-lombok class which provokes the same error:

package example.model.to;

public class CarDetail {
	private String model;

	private CarDetail(String model) {
		this.model = model;
	}

	public static CarDetailBuilder builder() {
		return new CarDetailBuilder();
	}

	public String getModel() {
		return this.model;
	}

	public void setModel(String model) {
		this.model = model;
	}

	public static class CarDetailBuilder {
		private String model;

		CarDetailBuilder() {
		}

		public CarDetail.CarDetailBuilder model(String model) {
			this.model = model;
			return this;
		}

		public CarDetail build() {
			return new CarDetail(model);
		}

		public String toString() {
			return "CarDetail.CarDetailBuilder(model=" + this.model + ")";
		}
	}
}

[filiphr]

Sorry I didn't see that you are using update mapping. In this case we can't use the builder and we would use the setters only.

I understand the problem now. Can you try with 1.4.0-SNAPSHOT? I think that there was a similar problem and we have fixed it on master.

[mfriess2]

Thanks & sure, I will build it and let you know soon.

[mfriess2]

I tried it out with 076f3ba and unfortunately it did not work.
I uploaded the full example to: https://github.com/mfriess2/mapstruct-issue-1997

[drenda]

@filiphr Could my question here be related to this issue? Any possible workaround? Thanks

[cedricwalter]

I can confirm the issue is still in version 1.4.1.Final

Any workaround?

[aalnaw2s]

I am also confirming the same bug with the last version 1.4.1.Final.
the proposed solutions above are not working.

[thunderhook]

@filiphr I can confirm that the problem starts appearing with lombok 1.18.14.

To reproduce this, adapt the mapstruct-lombok module in mapstruct-examples the following way:
Add @Builder on class Target and build the module. You will see that the mapper uses the builder.

Now, set <org.projectlombok.version> to 1.18.14 and rebuild the module. I have see randomly two issues

• java: No property named "test" exists in source parameter(s). Did you mean "null"? ... that alone may be a symptom that mapstruct can't read the source property from a @Data annotated class
• the mapper tries to use a no-arg-constructor and does not use the builder

I hope this helps investigating the underlying problem.

BTW: lombok-mapstruct-binding did not solve the problem, neither as dependency, nor as annotation processor path.

[filiphr]

@thunderhook is the problem there with 1.18.16? According to the Lombok changelog 1.18.14 is broken and shouldn't be used

[thunderhook]

Ah sorry, yes, this is reproducable with 1.18.16 as well.

[filiphr]

@thunderhook are you by any chance using Java 8 to do the compilation?

lombok-mapstruct-binding does not work on Java 8 have a look at projectlombok/lombok#2616. We have an open PR (mapstruct/mapstruct-examples#111) to update our examples to use the latest Lombok and the CI is green for Java 9+

[thunderhook]

@thunderhook are you by any chance using Java 8 to do the compilation?

lombok-mapstruct-binding does not work on Java 8 have a look at rzwitserloot/lombok#2616. We have an open PR (mapstruct/mapstruct-examples#111) to update our examples to use the latest Lombok and the CI is green for Java 9+

Thanks for clarification. Yes I am using Java 8. You are right, choosing a higher Java version works at least with maven.

Changing to 9 (or 11, or 15, that's what i've tried) also shows java: No property named "test" exists in source parameter(s). Did you mean "null"? but only in IntelliJ.

From my own test-project using Java 15 this is also reproducable (that was easier than adapting the mapstruct-examples project).

with something like

@Builder
@Value
public class CustomerDTO {

    int customerNumber;
    String name;
}

IntelliJ generated mapper:

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2020-11-21T17:47:56+0100",
    comments = "version: 1.4.1.Final, compiler: javac, environment: Java 15.0.1 (Oracle Corporation)"
)
public class CustomerMapperImpl implements CustomerMapper {

    @Override
    public CustomerDTO map(CustomerEntity source) {
        if ( source == null ) {
            return null;
        }

        CustomerDTO customerDTO = new CustomerDTO();
        // <- compile error java: constructor CustomerDTO in class bug.mapstruct.CustomerDTO cannot be applied to given types;
        //    required: int,java.lang.String
        //    found:    no arguments

        return customerDTO;
    }
}

Maven generated mapper:

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2020-11-21T17:51:38+0100",
    comments = "version: 1.4.1.Final, compiler: javac, environment: Java 15.0.1 (Oracle Corporation)"
)
public class CustomerMapperImpl implements CustomerMapper {

    @Override
    public CustomerDTO map(CustomerEntity source) {
        if ( source == null ) {
            return null;
        }

        CustomerDTOBuilder customerDTO = CustomerDTO.builder();

        customerDTO.customerNumber( (int) source.getCustomerNumber() );
        customerDTO.name( source.getName() );

        return customerDTO.build();
    }
}

If I can provide any more info (mvn/idea log), or if this should be an own ticket, please let me know!

Edit: Ahh, damn! I wrote the annotation processor configuration wrong. Sorry. It is working now as intended! Thanks!

[metao1]

I still have this problem. I want to force map construct to use the builder method instead.

Model:

@Value
@Builder
@AllArgsConstructor(access = AccessLevel.PRIVATE)
public class Student {
    String name;
    int id;
}

Mapper Class:

@Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.WARN)
public interface DTOMapper {
    Student map(Student student);
}
```
```

 error: LogConfigDTO does not have an accessible constructor.
    LogConfigDTO mapLogConfigToDTO(ConfigModel configModel);
                 ^
```

[filiphr]

@metao1 seems like you have cross posted this here and in the Lombok issue tracker projectlombok/lombok#2804. MapStruct by default uses builders (if it can see them), see projectlombok/lombok#1538 for more information

[FARHANE]

Same problem
java 15
lombok 1.18.20
mapstruct 1.4.2.Final

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

@Value
@Builder(toBuilder = true)
@AllArgsConstructor(access = AccessLevel.PRIVATE)
@Jacksonized
public class MyClass implements MyInterface{

}

MyClass  does not have an accessible constructor.