Add a way to configure DeserializerCache Jackson uses

src/main/java/com/fasterxml/jackson/databind/CacheProvider.java

@@ -0,0 +1,62 @@
+package com.fasterxml.jackson.databind;
+
+import com.fasterxml.jackson.databind.util.LookupCache;
+
+/**
+ * Container for {@link LookupCache} instances to use to override default cache implementations used.
+ * Should only be configured via {@link com.fasterxml.jackson.databind.json.JsonMapper.Builder#cacheProvider(CacheProvider)}.
+ * 
+ * @since 2.16
+ */
+public class CacheProvider
+    implements java.io.Serializable
+{
+    private static final long serialVersionUID = 1L; // 2.6
+
+    protected LookupCache<JavaType, JsonDeserializer<Object>> _deserializerCache;
+
+    protected CacheProvider() { }
+
+    protected CacheProvider setDeserializerCache(LookupCache<JavaType, JsonDeserializer<Object>> cache) {
+        _deserializerCache = cache;
+        return this;
+    }
+
+    /*
+    /**********************************************************
+    /* Builder Initialization
+    /**********************************************************
+     */
+
+    public static CacheProvider.Builder builder() {
+        return new Builder(new CacheProvider());
+    }
+
+    public LookupCache<JavaType, JsonDeserializer<Object>> provideForDeserializerCache() {
+        return _deserializerCache;
+    }
+
+    public static class Builder {
+
+        protected final CacheProvider cacheProvider;
+
+        public Builder(CacheProvider cacheProvider) {
+            this.cacheProvider = cacheProvider;
+        }
+
+        public CacheProvider build() {
+            return cacheProvider;
+        }
+
+        /*
+        /**********************************************************
+        /* Configuration using Builder
+        /**********************************************************
+         */
+
+        public Builder forDeserializerCache(LookupCache<JavaType, JsonDeserializer<Object>> cache) {
+            cacheProvider.setDeserializerCache(cache);
+            return this;
+        }
+    }
+}

src/main/java/com/fasterxml/jackson/databind/DeserializationConfig.java

@@ -101,6 +101,13 @@ public final class DeserializationConfig
      */
     protected final int _formatReadFeaturesToChange;
 
+    /**
+     * Used to provide custom cache implementation in downstream components.
+     * 
+     * @since 2.16
+     */
+    protected CacheProvider _cacheProvider;
+
     /*
     /**********************************************************
     /* Life-cycle, primary constructors for new instances
@@ -325,6 +332,23 @@ protected DeserializationConfig(DeserializationConfig src,
         _formatReadFeaturesToChange = src._formatReadFeaturesToChange;
     }
 
+    /**
+     * @since 2.16
+     */
+    protected DeserializationConfig(DeserializationConfig src, CacheProvider cacheProvider) {
+        super(src);
+        _deserFeatures = src._deserFeatures;
+        _problemHandlers = src._problemHandlers;
+        _nodeFactory = src._nodeFactory;
+        _coercionConfigs = src._coercionConfigs;
+        _ctorDetector = src._ctorDetector;
+        _parserFeatures = src._parserFeatures;
+        _parserFeaturesToChange = src._parserFeaturesToChange;
+        _formatReadFeatures = src._formatReadFeatures;
+        _formatReadFeaturesToChange = src._formatReadFeaturesToChange; 
+        _cacheProvider = cacheProvider;
+    }
+
     // for unit tests only:
     protected BaseSettings getBaseSettings() { return _base; }
 
@@ -922,6 +946,13 @@ public ConstructorDetector getConstructorDetector() {
         return _ctorDetector;
     }
 
+    /**
+     * @since 2.16
+     */
+    public CacheProvider getCacheProvider() {
+        return _cacheProvider;
+    }
+
     /*
     /**********************************************************
     /* Introspection methods
@@ -1046,4 +1077,12 @@ public CoercionAction findCoercionFromBlankString(LogicalType targetType,
         return _coercionConfigs.findCoercionFromBlankString(this,
                 targetType, targetClass, actionIfBlankNotAllowed);
     }
+
+    /**
+     * @return New instance of {@link DeserializationConfig} with configured {@link CacheProvider}.
+     * @since 2.16
+     */
+    public DeserializationConfig withCacheProvider(CacheProvider cacheProvider) {
+        return (cacheProvider == _cacheProvider) ? this : new DeserializationConfig(this, cacheProvider);
+    }
 }

src/main/java/com/fasterxml/jackson/databind/DeserializationContext.java

@@ -206,7 +206,7 @@ protected DeserializationContext(DeserializationContext src,
             DeserializationConfig config, JsonParser p,
             InjectableValues injectableValues)
     {
-        _cache = src._cache;
+        _cache = src._cache.withCache(config.getCacheProvider());
         _factory = src._factory;
         // 08-Jun-2020. tatu: Called only for `ObjectMapper.canDeserialize()`
         //    (see [databind#2749]), not sure what's the best work-around but
@@ -230,7 +230,7 @@ protected DeserializationContext(DeserializationContext src,
     protected DeserializationContext(DeserializationContext src,
             DeserializationConfig config)
     {
-        _cache = src._cache;
+        _cache = src._cache.withCache(config.getCacheProvider());
         _factory = src._factory;
         _readCapabilities = null;
 

src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java

@@ -2267,6 +2267,16 @@ public ObjectMapper setConstructorDetector(ConstructorDetector cd) {
         return this;
     }
 
+    /**
+     * Method for specifying {@link CacheProvider} to provide Cache instances to be used in components downstream.
+     *
+     * @since 2.16
+     */
+    public ObjectMapper setCacheProvider(CacheProvider cacheProvider) {
+        _deserializationConfig = _deserializationConfig.withCacheProvider(cacheProvider);
+        return this;
+    }
+
     /**
      * Method for adding specified {@link DeserializationProblemHandler}
      * to be used for handling specific problems during deserialization.

src/main/java/com/fasterxml/jackson/databind/cfg/MapperBuilder.java

@@ -606,6 +606,14 @@ public B clearProblemHandlers() {
         return _this();
     }
 
+    /**
+     * @since 2.16
+     */
+    public B cacheProvider(CacheProvider cacheProvider) {
+        _mapper.setCacheProvider(cacheProvider);
+        return _this();
+    }
+
     /*
     /**********************************************************************
     /* Changing global defaults

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

@@ -10,6 +10,7 @@
 import com.fasterxml.jackson.databind.util.ClassUtil;
 import com.fasterxml.jackson.databind.util.Converter;
 import com.fasterxml.jackson.databind.util.LRUMap;
+import com.fasterxml.jackson.databind.util.LookupCache;
 
 /**
  * Class that defines caching layer between callers (like
@@ -33,8 +34,10 @@ public final class DeserializerCache
      * We will also cache some dynamically constructed deserializers;
      * specifically, ones that are expensive to construct.
      * This currently means bean, Enum and container deserializers.
+     * <p>
+     * Since 2.16, changed its type from {@link LRUMap} to {@link LookupCache}
      */
-    final protected LRUMap<JavaType, JsonDeserializer<Object>> _cachedDeserializers;
+    final protected LookupCache<JavaType, JsonDeserializer<Object>> _cachedDeserializers;
 
     /**
      * During deserializer construction process we may need to keep track of partially
@@ -59,6 +62,23 @@ public DeserializerCache(int maxSize) {
         _cachedDeserializers = new LRUMap<>(initial, maxSize);
     }
 
+    /**
+     * @since 2.16
+     */
+    protected DeserializerCache(LookupCache<JavaType, JsonDeserializer<Object>> cachedDeserializers) {
+        _cachedDeserializers = cachedDeserializers;
+    }
+
+    /**
+     * @since 2.16
+     */
+    public DeserializerCache withCache(CacheProvider cacheProvider) {
+        if (cacheProvider == null) {
+            return this;
+        }
+        return new DeserializerCache(cacheProvider.provideForDeserializerCache()); 
+    }
+
     /*
     /**********************************************************
     /* JDK serialization handling

src/test/java/com/fasterxml/jackson/databind/cfg/CacheProviderTest.java

@@ -0,0 +1,67 @@
+package com.fasterxml.jackson.databind.cfg;
+
+import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import com.fasterxml.jackson.databind.util.LookupCache;
+import org.junit.Test;
+
+import java.util.HashMap;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * <a href="https://github.com/FasterXML/jackson-databind/issues/2502">
+ * [databind#2502] Test for adding a way to configure Caches Jackson uses</a>
+ * 
+ * @since 2.16
+ */
+public class CacheProviderTest
+{
+
+    static class RandomBean {
+        public int point;
+    }
+
+    static class SimpleTestCache implements LookupCache<JavaType, JsonDeserializer<Object>> {
+
+        final HashMap<JavaType, JsonDeserializer<Object>> cache = new HashMap<>();
+
+        @Override
+        public int size(){
+            return cache.size();
+        }
+
+        @Override
+        public JsonDeserializer<Object> get(Object key) {
+            return cache.get(key);
+        }
+
+        @Override
+        public JsonDeserializer<Object> put(JavaType key, JsonDeserializer<Object> value) {
+            return cache.put(key, value);
+        }
+
+        @Override
+        public JsonDeserializer<Object> putIfAbsent(JavaType key, JsonDeserializer<Object> value) {
+            return cache.putIfAbsent(key, value);
+        }
+
+        @Override
+        public void clear() {
+            cache.clear();
+        }
+    }
+
+    @Test
+    public void testCacheConfig() throws Exception
+    {
+        CacheProvider cacheProvider = CacheProvider.builder()
+                .forDeserializerCache(new SimpleTestCache())
+                .build();
+
+        ObjectMapper mapper = JsonMapper.builder().cacheProvider(cacheProvider).build();
+
+        RandomBean bean = mapper.readValue("{\"point\":24}", RandomBean.class);
+        assertEquals(24, bean.point);
+    }
+}