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

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

@@ -1268,10 +1268,12 @@ public KeyDeserializer createKeyDeserializer(DeserializationContext ctxt,
         throws JsonMappingException
     {
         final DeserializationConfig config = ctxt.getConfig();
-        BeanDescription beanDesc = null;
-        KeyDeserializer deser = null;
-        if (_factoryConfig.hasKeyDeserializers()) {
-            beanDesc = config.introspectClassAnnotations(type);
+        final BeanDescription beanDesc = config.introspectClassAnnotations(type);
+
+        // [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) {
@@ -1282,17 +1284,10 @@ public KeyDeserializer createKeyDeserializer(DeserializationContext ctxt,
 
         // the only non-standard thing is this:
         if (deser == null) {
-            // [databind#2452]: Support `@JsonDeserialize(keyUsing = ...)`
-            if (beanDesc == null) {
-                beanDesc = config.introspectClassAnnotations(type.getRawClass());
-            }
-            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/ser/TestKeyDeserializerOverwritten.java

@@ -0,0 +1,63 @@
+package com.fasterxml.jackson.databind.ser;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+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 org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+// [databind#4444]
+public class TestKeyDeserializerOverwritten {
+    @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");
+        }
+    }
+
+    TypeReference<Map<MyKey, String>> typeRef = new TypeReference<>() {};
+
+    @Test
+    void withoutForClass() throws JsonProcessingException {
+        ObjectMapper mapper = new ObjectMapper();
+        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 JsonProcessingException {
+        SimpleModule sm = new SimpleModule();
+        sm.addKeyDeserializer(MyKey.class, new ForMapper());
+
+        ObjectMapper mapper = new ObjectMapper().registerModule(sm);
+        Map<MyKey, String> result = mapper.readValue("{\"foo\":null}", typeRef);
+
+        assertEquals("foo-class", result.keySet().stream().findFirst().get().value);
+    }
+}