From 29c61bb283b3eac1af4d6fd96dc834871f861479 Mon Sep 17 00:00:00 2001
From: Claudio Atzori <claudio.atzori@isti.cnr.it>
Date: Wed, 8 Feb 2023 16:04:48 +0100
Subject: [PATCH] avoid NPEs

---
 src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java b/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java
index 62669b0..922f386 100644
--- a/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java
+++ b/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java
@@ -33,7 +33,7 @@ public class StructuredProperty implements Serializable {
 	public String toComparableString() {
 		return Stream
 			.of(
-				getQualifier().toComparableString(),
+				Optional.ofNullable(getQualifier()).map(q -> q.toComparableString()).orElse(""),
 				Optional.ofNullable(getValue()).map(String::toLowerCase).orElse(""))
 			.filter(StringUtils::isNotBlank)
 			.collect(Collectors.joining("||"));