Mapping from Map to Map and specify source and target keys

[JM92103]

Use case

I have a use case where I need to convert a Map<String, String> to a Map<String, String> but manipulate the keys. Currently I am trying to do

@Mapping(target = "value",  source = "Cash_Amount")
@Mapping(target = "valueDate",  source = "Date_Of_Money_Movement")
Map<String, String> fromCsvToStpTransaction(Map<String, String> rec);

But the generated code is ignoring these values and just doing a basic Map conversion like below

@Override
public Map<String, String> fromCsvToStpTransaction(Map<String, String> rec) {
    if ( rec == null ) {
        return null;
    }

    Map<String, String> map = new LinkedHashMap<String, String>( Math.max( (int) ( rec.size() / .75f ) + 1, 16 ) );

    for ( java.util.Map.Entry<String, String> entry : rec.entrySet() ) {
        String key = entry.getKey();
        String value = entry.getValue();
        map.put( key, value );
    }

    return map;
}

Generated Code

I would expect the generated code to look something like

@Override
public Map<String, String> fromCsvToStpTransaction(Map<String, String> rec) {
    if ( rec == null ) {
        return null;
    }

    Map<String, String> map = new LinkedHashMap<String, String>( Math.max( (int) ( rec.size() / .75f ) + 1, 16 ) );

    if ( rec.containsKey("Cash_Amount") {
        map.put("value", rec.get("Cash_Amount");
    }

    if ( rec.containsKey("Date_Of_Money_Movement") {
        map.put("valueDate", rec.get("Date_Of_Money_Movement");
    }
    //an else would be nice as well to assume mapping of non matched values 
    else {
        for ( java.util.Map.Entry<String, String> entry : rec.entrySet() ) {
            String key = entry.getKey();
            String value = entry.getValue();
            map.put( key, value );
        }
    }

    return map;
}

Possible workarounds

No response

MapStruct Version

1.5.5

[filiphr]

This is a valid request @JM92103, I don't see why something like this shouldn't be supported. However, I would expect the implementation to look like:

public class MyMapperImpl implements MyMapper {

    private final Map<String, String> fromCsvToStpTransactionKeyMappings;

    public MyMapperImpl() {
        this.fromCsvToStpTransactionKeyMappings = new HashMap<>();
        this.fromCsvToStpTransactionKeyMappings.put( "Cash_Amount", "value" );
        this.fromCsvToStpTransactionKeyMappings.put( "Date_Of_Money_Movement", "valueDate" );
    }

    @Override
    public Map<String, String> fromCsvToStpTransaction(Map<String, String> rec) {
        if ( rec == null ) {
            return null;
        }

        Map<String, String> map = new LinkedHashMap<>( Math.max( (int) ( rec.size() / .75f ) + 1, 16 ) );

        for ( java.util.Map.Entry<String, String> entry : rec.entrySet() ) {
            String key = entry.getKey();
            String value = entry.getValue();
            map.put( this.fromCsvToStpTransactionKeyMappings.getOrDefault( key, key ), value );
        }

        return map;
    }
}

The fromCsvToStpTransactionKeyMappings should only be created if the mapping method has @Mapping.

I'll put this for "up for grabs" in case someone from the community is interested in working on this.