Fixed so that KeyDeserializer set by annotation is not overwritten by KeyDeserializer set in the mapper

release-notes/CREDITS-2.x

@@ -1850,6 +1850,10 @@ wrongwrong (@k163377)
  * Reported #4878: When serializing a Map via Converter(StdDelegatingSerializer),
    a NullPointerException is thrown due to missing key serializer
   (2.18.3)
+ * Contributed fix for #4444: The `KeyDeserializer` specified in the class with
+   `@JsonDeserialize(keyUsing = ...)` is overwritten by the `KeyDeserializer`
+    specified in the `ObjectMapper`.
+  (2.18.3)
 
 Bernd Ahlers (@bernd)
  * Reported #4742: Deserialization with Builder, External type id, `@JsonCreator` failing

release-notes/VERSION-2.x

@@ -6,6 +6,9 @@ Project: jackson-databind
 
 2.18.3 (not yet released)
 
+#4444: The `KeyDeserializer` specified in the class with `@JsonDeserialize(keyUsing = ...)`
+  is overwritten by the `KeyDeserializer` specified in the `ObjectMapper`.
+ (fix by @wrongwrong)
 #4827: Subclassed Throwable deserialization fails since v2.18.0 - no creator
   index for property 'cause'
  (reported by @nilswieber)

src/main/java/com/fasterxml/jackson/databind/deser/BasicDeserializerFactory.java

@@ -1269,8 +1269,11 @@ public KeyDeserializer createKeyDeserializer(DeserializationContext ctxt,
     {
         final DeserializationConfig config = ctxt.getConfig();
         final BeanDescription beanDesc = config.introspectClassAnnotations(type);
-        KeyDeserializer deser = null;
-        if (_factoryConfig.hasKeyDeserializers()) {
+
+        // [databind#2452]: Support `@JsonDeserialize(keyUsing = ...)`
+        KeyDeserializer deser = findKeyDeserializerFromAnnotation(ctxt, beanDesc.getClassInfo());
+
+        if (deser == null && _factoryConfig.hasKeyDeserializers()) {
             for (KeyDeserializers d  : _factoryConfig.keyDeserializers()) {
                 deser = d.findKeyDeserializer(type, config, beanDesc);
                 if (deser != null) {
@@ -1281,14 +1284,10 @@ public KeyDeserializer createKeyDeserializer(DeserializationContext ctxt,
 
         // the only non-standard thing is this:
         if (deser == null) {
-            // [databind#2452]: Support `@JsonDeserialize(keyUsing = ...)`
-            deser = findKeyDeserializerFromAnnotation(ctxt, beanDesc.getClassInfo());
-            if (deser == null) {
-                if (type.isEnumType()) {
-                    deser = _createEnumKeyDeserializer(ctxt, type);
-                } else {
-                    deser = StdKeyDeserializers.findStringBasedKeyDeserializer(config, type);
-                }
+            if (type.isEnumType()) {
+                deser = _createEnumKeyDeserializer(ctxt, type);
+            } else {
+                deser = StdKeyDeserializers.findStringBasedKeyDeserializer(config, type);
             }
         }
         // and then post-processing

src/test/java/com/fasterxml/jackson/databind/deser/jdk/CustomMapKeyDeserializer4444Test.java

@@ -0,0 +1,67 @@
+package com.fasterxml.jackson.databind.deser.jdk;
+
+import java.io.IOException;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.KeyDeserializer;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+// [databind#4444]
+public class CustomMapKeyDeserializer4444Test extends DatabindTestUtil
+{
+    @JsonDeserialize(keyUsing = ForClass.class)
+    static class MyKey {
+        private final String value;
+
+        MyKey(String value) {
+            this.value = value;
+        }
+    }
+
+    static class ForClass extends KeyDeserializer {
+        @Override
+        public Object deserializeKey(String key, DeserializationContext ctxt) throws IOException {
+            return new MyKey(key + "-class");
+        }
+    }
+
+    static class ForMapper extends KeyDeserializer {
+        @Override
+        public Object deserializeKey(String key, DeserializationContext ctxt) throws IOException {
+            return new MyKey(key + "-mapper");
+        }
+    }
+
+    // It is not declared as new TypeReference<> because it causes a compile error in Java 8.
+    TypeReference<Map<MyKey, String>> typeRef = new TypeReference<Map<MyKey, String>>() {
+    };
+
+    @Test
+    void withoutForClass() throws Exception {
+        ObjectMapper mapper = newJsonMapper();
+        Map<MyKey, String> result = mapper.readValue("{\"foo\":null}", typeRef);
+
+        assertEquals("foo-class", result.keySet().stream().findFirst().get().value);
+    }
+
+    // The KeyDeserializer set by the annotation must not be overwritten by the KeyDeserializer set in the mapper.
+    @Test
+    void withForClass() throws Exception {
+        SimpleModule sm = new SimpleModule();
+        sm.addKeyDeserializer(MyKey.class, new ForMapper());
+
+        ObjectMapper mapper = jsonMapperBuilder().addModule(sm).build();
+        Map<MyKey, String> result = mapper.readValue("{\"foo\":null}", typeRef);
+
+        assertEquals("foo-class", result.keySet().stream().findFirst().get().value);
+    }
+}