Feedback on new mapping-map-to-bean feature

[Rich MacDonald]

I just had the opportunity to try the new beta feature of mapping HashMap to an object and thought I'd share my experience. I appreciate the effort the developers are putting into this tool.

- Not relevant to the new feature, but is it possible to add a configuration to make the methods final? That would really help out the JIT.

- The general pattern is as follows:

   if ( map.containsKey( "theKey" ) ) {

       target.setValue( map.get( " theKey " )   );

   }

That causes two map operations (containsKey and get) and I don't believe the JIT will be able to resolve this to a single operation. Why not write the more efficient:

   <Type> theValue = map.get( " theKey " );

   if (theValue != null){

       target.setValue(theValue);

   }

The map code has trouble working with Map<String,Object>. So if the values are Objects, Strings, Integers, ints, etc, there seems to be no way to make it work. I get ambiguous error no matter what I try. A typical use case would be processing a json string that was deserialized to a Map<String,Object>.

[Rich MacDonald]

//Example test class

public class TestTarget {

public int myIntPrim;

public Integer myInteger;

public long myLongPrim;

public Long myLong;

public String myString;

public TestTarget otherTarget;

}

--------------------------------------------------

Following class causes the following errors:

Multiple markers at this line

- Ambiguous mapping methods found for mapping property "java.lang.Object myLong" to java.lang.Long: long mapLongPrim(java.lang.Object 

prop), java.lang.Long mapLong(java.lang.Object prop). See https://mapstruct.org/faq/#ambiguous for more info.

- Ambiguous mapping methods found for mapping property "java.lang.Object myLongPrim" to long: int mapIntPrim(java.lang.Object prop), java.

lang.Integer mapInt(java.lang.Object prop), long mapLongPrim(java.lang.Object prop), java.lang.Long mapLong(java.lang.Object prop). See https:

//mapstruct.org/faq/#ambiguous for more info.

- Ambiguous mapping methods found for mapping property "java.lang.Object myIntPrim" to int: int mapIntPrim(java.lang.Object prop), java.lang.

Integer mapInt(java.lang.Object prop). See https://mapstruct.org/faq/#ambiguous for more info.

- Ambiguous mapping methods found for mapping property "java.lang.Object myInteger" to java.lang.Integer: int mapIntPrim(java.lang.Object 

prop), java.lang.Integer mapInt(java.lang.Object prop). See https://mapstruct.org/faq/#ambiguous for more info.

import java.util.Map;

import org.mapstruct.Mapper;

import org.mapstruct.MappingTarget;

@Mapper

public interface TestTargetMapper {

void test(Map<String, Object> map, @MappingTarget TestTarget target);

default int mapIntPrim(Object prop) {

return prop == null ? 0 : ((Integer) prop).intValue();

}

default Integer mapInt(Object prop) {

return prop == null ? null : (Integer) prop;

}

default long mapLongPrim(Object prop) {

return prop == null ? 0 : ((Long) prop).longValue();

}

default Long mapLong(Object prop) {

return prop == null ? null : (Long) prop;

}

default String mapString(Object prop) {

return (String) prop;

}

default TestTarget mapTarget(Object targetRef) {

// lookup reference todo

return null;

}

}

-----------------------------------------------------------

Try to remove the primitive methods:

Ambiguous mapping methods found for mapping property "java.lang.Object myLongPrim" to long: java.lang.Integer mapInt(java.lang.Object prop), java.lang.Long 

 mapLong(java.lang.Object prop). See https://mapstruct.org/faq/#ambiguous for more info.

@Mapper

public interface TestTargetMapper {

void test(Map<String, Object> map, @MappingTarget TestTarget target);

default Integer mapInt(Object prop) {

return prop == null ? null : (Integer) prop;

}

default Long mapLong(Object prop) {

return prop == null ? null : (Long) prop;

}

default String mapString(Object prop) {

return (String) prop;

}

default TestTarget mapTarget(Object targetRef) {

// lookup reference todo

return null;

}

}

-----------------------------------------------------------

Remove the offending mapInt method:

Multiple markers at this line

- Ambiguous 2step methods found, mapping Object map to int. Found conversionY( methodX ( parameter ) ): conversionY: Long-->int, method

(s)X: java.lang.Long mapLong(java.lang.Object prop); conversionY: String-->int, method(s)X: java.lang.String mapString(java.lang.Object prop); .

- Can't map property "java.lang.Object myInteger" to "java.lang.Integer myInteger". Consider to declare/implement a mapping method: "java.lang.

Integer map(java.lang.Object value)".

- Can't map property "java.lang.Object myIntPrim" to "int myIntPrim". Consider to declare/implement a mapping method: "int map(java.lang.

Object value)".

- Ambiguous 2step methods found, mapping Object map to Integer. Found conversionY( methodX ( parameter ) ): conversionY: Long-->Integer, 

method(s)X: java.lang.Long mapLong(java.lang.Object prop); conversionY: String-->Integer, method(s)X: java.lang.String mapString(java.lang.Object prop); .

@Mapper

public interface TestTargetMapper {

void test(Map<String, Object> map, @MappingTarget TestTarget target);

default Long mapLong(Object prop) {

return prop == null ? null : (Long) prop;

}

default String mapString(Object prop) {

return (String) prop;

}

default TestTarget mapTarget(Object targetRef) {

// lookup reference todo

return null;

}

}