org.drools.workbench.models.guided.dtable.shared.model.GuidedDecisionTable52 unmarshal =
org.drools.workbench.models.guided.dtable.backend.GuidedDTXMLPersistence.getInstance().unmarshal(
new String(Files.readAllBytes(Paths.get("src/main/resources/guidedTable.gdst")))
);
String drl = org.drools.workbench.models.guided.dtable.backend.GuidedDTDRLPersistence.getInstance().marshal(unmarshal);
System.out.println(drl);
add this dep to your maven pom
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-workbench-models-guided-dtable</artifactId>
</dependency>