From c54fc82e475843f3fbaa2dc27644d662728f188d Mon Sep 17 00:00:00 2001
From: Alex Blekhman <ablekhman@atlassian.com>
Date: Mon, 27 Mar 2023 19:47:25 +1100
Subject: [PATCH] Fix AtomicReference marshalling. Closes #326.

---
 .../extended/AtomicReferenceConverter.java    | 30 +++++++++++--------
 .../acceptance/Concurrent15TypesTest.java     |  5 ++++
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/xstream/src/java/com/thoughtworks/xstream/converters/extended/AtomicReferenceConverter.java b/xstream/src/java/com/thoughtworks/xstream/converters/extended/AtomicReferenceConverter.java
index a823f0de6..69de63d52 100644
--- a/xstream/src/java/com/thoughtworks/xstream/converters/extended/AtomicReferenceConverter.java
+++ b/xstream/src/java/com/thoughtworks/xstream/converters/extended/AtomicReferenceConverter.java
@@ -40,23 +40,29 @@ public boolean canConvert(final Class type) {
     }
 
     public void marshal(final Object source, final HierarchicalStreamWriter writer, final MarshallingContext context) {
-        final AtomicReference ref = (AtomicReference)source; 
-        writer.startNode(mapper.serializedMember(AtomicReference.class, "value"));
-
+        final AtomicReference ref = (AtomicReference)source;
         final Object object = ref.get();
-        final String name = mapper.serializedClass(object!= null ? object.getClass() : null);
-        writer.addAttribute(mapper.aliasForSystemAttribute("class"), name);
-        context.convertAnother(ref.get());
-        writer.endNode();
+        if (object != null) {
+            writer.startNode(mapper.serializedMember(AtomicReference.class, "value"));
+
+            final String name = mapper.serializedClass(object.getClass());
+            writer.addAttribute(mapper.aliasForSystemAttribute("class"), name);
+            context.convertAnother(object);
+            writer.endNode();
+        }
     }
 
     public Object unmarshal(final HierarchicalStreamReader reader, final UnmarshallingContext context) {
-        reader.moveDown();
+        if (reader.hasMoreChildren()) {
+            reader.moveDown();
 
-        final Class type = HierarchicalStreams.readClassType(reader, mapper);
-        final Object value = context.convertAnother(context, type);
-        reader.moveUp();
-        return new AtomicReference(value);
+            final Class type = HierarchicalStreams.readClassType(reader, mapper);
+            final Object value = context.convertAnother(context, type);
+            reader.moveUp();
+            return new AtomicReference(value);
+        } else {
+            return new AtomicReference();
+        }
     }
 
 }
diff --git a/xstream/src/test/com/thoughtworks/acceptance/Concurrent15TypesTest.java b/xstream/src/test/com/thoughtworks/acceptance/Concurrent15TypesTest.java
index 3670965fc..ea436fe08 100644
--- a/xstream/src/test/com/thoughtworks/acceptance/Concurrent15TypesTest.java
+++ b/xstream/src/test/com/thoughtworks/acceptance/Concurrent15TypesTest.java
@@ -117,6 +117,11 @@ public void testAtomicReferenceWithOldFormat() {
             + "</java.util.concurrent.atomic.AtomicReference>")).get());
     }
 
+    public void testEmptyAtomicReference() {
+        final AtomicReference atomicRef = new AtomicReference();
+        assertBothWays(atomicRef, "<atomic-reference/>");
+    }
+
     public void testAtomicReferenceWithAlias() {
         xstream.aliasField("junit", AtomicReference.class, "value");
         final AtomicReference atomicRef = new AtomicReference("test");