{Executor, MappingFactory}: support language tags for constants

Author: DylanVanAssche

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Better handle unsupported reference formulation (See [issue 247](https://github.com/RMLio/rmlmapper-java/issues/247))
 - Graph Maps with default graph must not be ignored (See [issue 252](https://github.com/RMLio/rmlmapper-java/issues/252))
 - Honor datatypes for constants (See [issue 251](https://github.com/RMLio/rmlmapper-java/issues/251))
+- Honor language tags for constants (See [issue 251](https://github.com/RMLio/rmlmapper-java/issues/251))
 
 ## [7.3.2] - 2025-03-04
 

src/main/java/be/ugent/rml/Executor.java

@@ -373,7 +373,7 @@ private List<PredicateObjectGraph> combineMultiplePOGs(List<ProvenancedTerm> pre
                 p -> objects.forEach(
                         o -> graphs.forEach(
                                 g -> {
-                                    if (g.getTerm().equals(new NamedNode(NAMESPACES.RML2 + "defaultGraph"))) {
+                                    if (g != null && g.getTerm().equals(new NamedNode(NAMESPACES.RML2 + "defaultGraph"))) {
                                         results.add(new PredicateObjectGraph(p, o, null));
                                     } else {
                                         results.add(new PredicateObjectGraph(p, o, g));

src/main/java/be/ugent/rml/MappingFactory.java

@@ -202,8 +202,16 @@ private void parseObjectMapsAndShortcutsWithCallback(Term termMap, BiConsumer<Ma
             SingleRecordFunctionExecutor fn = new ConstantExtractor(o.getValue());
 
             if (o instanceof Literal) {
-                Term datatype = new NamedNode(((Literal) o).getDatatype().toString());
-                gen = new LiteralGenerator(fn, datatype);
+                if (((Literal) o).getDatatype() != null) {
+                    Term datatype = new NamedNode(((Literal) o).getDatatype().toString());
+                    gen = new LiteralGenerator(fn, datatype);
+                } else if (((Literal) o).getLanguage().isPresent()) {
+                    SingleRecordFunctionExecutor executor = new ConstantExtractor(((Literal) o).getLanguage().get());
+                    gen = new LiteralGenerator(fn, executor);
+                } else {
+                    gen = new LiteralGenerator(fn);
+                }
+
             } else {
                 gen = new NamedNodeGenerator(fn, baseIRI, strictMode);
             }