F grpc null values

Summary

Fixes the NullPointerException which was throws when executing SELECT queries on NULL Values, e.g. SELECT p1 FROM ENTITY WHERE p1 IS NULL. The implementation needs to be slightly different compared to SELECT p1 FROM ENTITY WHICH DOESN'T HAVE A p1 but the results must be the same.

Related: #311 (closed)

Focus

Actually there are three fixed bugs in this MR. The fix of the first revealed the second, which revealed the third. See annotations.

Test Environment

No manual testing required.

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• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
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src/test/java/org/caosdb/server/grpc/CaosDBToGrpcConvertersTest.java

@@ -6,7 +6,9 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 import java.util.TimeZone;
 import org.caosdb.api.entity.v1.Value.Builder;
 import org.caosdb.datetime.DateTimeFactory2;
+import org.caosdb.server.datatype.CollectionValue;
 import org.caosdb.server.datatype.GenericValue;
+import org.caosdb.server.datatype.ReferenceValue;
 import org.caosdb.server.datatype.Value;
 import org.caosdb.server.entity.EntityID;
 import org.caosdb.server.entity.FileProperties;
@@ -119,4 +121,53 @@ public class CaosDBToGrpcConvertersTest {
         "scalar_value {\n" + "  special_value: SPECIAL_VALUE_UNSPECIFIED\n" + "}\n",
         value.toString());
   }
+
+  @Test
+  public void testGetSelectedValueWithListOfReferenceValue() {
+    CollectionValue col = new CollectionValue();
+    Property p = new Property(new RetrieveEntity());
+    p.setName("Person");
+    p.setDatatype("List<Person>");
+
+    Property fullName1 = new Property(new RetrieveEntity());
+    fullName1.setName("full name");
+    fullName1.setDatatype("TEXT");
+    fullName1.setValue(new GenericValue("Harry Belafonte"));
+
+    RetrieveEntity person1 = new RetrieveEntity();
+    person1.addProperty(fullName1);
+    ReferenceValue val1 = new ReferenceValue(new EntityID(1234));
+    val1.setEntity(person1, false);
+    col.add(val1);
+
+    Property fullName2 = new Property(new RetrieveEntity());
+    fullName2.setName("full name");
+    fullName2.setDatatype("TEXT");
+    fullName2.setValue(new GenericValue("Louis Prima"));
+
+    RetrieveEntity person2 = new RetrieveEntity();
+    person2.addProperty(fullName2);
+    ReferenceValue val2 = new ReferenceValue(new EntityID(1234));
+    val2.setEntity(person2, false);
+    col.add(val2);
+    p.setValue(col);
+
+    RetrieveEntity entity = new RetrieveEntity();
+    entity.addProperty(p);
+
+    CaosDBToGrpcConverters converters = new CaosDBToGrpcConverters(null);
+    Builder value =
+        converters.getSelectedValue(
+            new Selection("Person").setSubSelection(new Selection("full name")), entity);
+    assertEquals(
+        "list_values {\n"
+            + "  values {\n"
+            + "    string_value: \"Harry Belafonte\"\n"
+            + "  }\n"
+            + "  values {\n"
+            + "    string_value: \"Louis Prima\"\n"
+            + "  }\n"
+            + "}\n",
+        value.toString());
+  }
 }