Fix #372

datatypes/src/main/java/com/fasterxml/jackson/datatype/jdk8/Jdk8Deserializers.java

@@ -26,7 +26,7 @@ public Jdk8Deserializers() {
     public Jdk8Deserializers(boolean cfgReadAbsentAsNull) {
         _cfgReadAbsentAsNull = cfgReadAbsentAsNull;
     }
-    
+
     @Override // since 2.7
     public JsonDeserializer<?> findReferenceDeserializer(ReferenceType refType,
             DeserializationConfig config, BeanDescription beanDesc,
@@ -52,4 +52,23 @@ public JsonDeserializer<?> findReferenceDeserializer(ReferenceType refType,
         }
         return null;
     }
+
+    // @since 2.18.5 wrt [modules-java8#372]
+    @Override
+    public JsonDeserializer<?> findBeanDeserializer(JavaType type,
+            DeserializationConfig config, BeanDescription beanDesc)
+        throws JsonMappingException
+    {
+        // 25-Jul-2025, tatu: [modules-java8#372] - work-around for misconfigured
+        //   `TypeFactory` that does not use `Jdk8TypeModifier`
+        if (type.hasRawClass(Optional.class)) {
+            // Not the cleanest but has to do: create properly resolved type;
+            // pass `null` for `contentTypeDeserializer` and `contentDeserializer`
+            // (to be resolver contextually)
+            JavaType refType = config.constructType(Optional.class);
+            return new OptionalDeserializer(refType, null, null, null,
+                    _cfgReadAbsentAsNull);
+        }
+        return null;
+    }
 }

datatypes/src/test/java/com/fasterxml/jackson/datatype/jdk8/OptionalTest.java

@@ -266,6 +266,17 @@ public void testTypeResolution() throws Exception
         assertTrue(t2.isCollectionLikeType());
     }
 
+    // [modules-java8#372]
+    public void testIssue372() throws Exception
+    {
+        JsonNode input = MAPPER.getNodeFactory().textNode("abc");
+        //JavaType type = MAPPER.getTypeFactory().constructType(Optional.class);
+        JavaType type = TypeFactory.defaultInstance().constructType(Optional.class);
+        //JavaType type = MAPPER.constructType(Optional.class);
+        Optional<?> value = MAPPER.readValue(MAPPER.treeAsTokens(input), type);
+        assertEquals(Optional.of("abc"), value);
+    }
+
     /*
     /**********************************************************
     /* Helper methods

release-notes/VERSION-2.x

@@ -8,6 +8,12 @@ Modules:
 === Releases ===
 ------------------------------------------------------------------------
 
+2.18.5 (not yet released)
+
+#372: `java.util.Optional` deserialisation fails when using `TypeFactory.defaultInstance`
+  for creating `JavaType` for `Optional<?>`
+ (reported by @mattlocker)
+
 2.18.4 (06-May-2025)
 
 #291: `InstantDeserializer` fails to parse negative numeric timestamp strings