Add a way to configure DeserializerCache Jackson uses

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

@@ -161,21 +161,11 @@ public abstract class DeserializationContext
     /**********************************************************
      */
 
-    protected DeserializationContext(DeserializerFactory df) {
-        this(df, null);
-    }
-
     protected DeserializationContext(DeserializerFactory df,
             DeserializerCache cache)
     {
-        if (df == null) {
-            throw new NullPointerException("Cannot pass null DeserializerFactory");
-        }
-        _factory = df;
-        if (cache == null) {
-            cache = new DeserializerCache();
-        }
-        _cache = cache;
+        _factory = Objects.requireNonNull(df);
+        _cache = Objects.requireNonNull(cache);
         _featureFlags = 0;
         _readCapabilities = null;
         _config = null;
@@ -199,6 +189,24 @@ protected DeserializationContext(DeserializationContext src,
         _attributes = src._attributes;
     }
 
+    /**
+     * @since 2.16
+     */
+    protected DeserializationContext(DeserializationContext src,
+             DeserializerCache cache)
+    {
+        _cache = cache;
+        _factory = src._factory;
+
+        _config = src._config;
+        _featureFlags = src._featureFlags;
+        _readCapabilities = src._readCapabilities;
+        _view = src._view;
+        _parser = src._parser;
+        _injectableValues = src._injectableValues;
+        _attributes = src._attributes;
+    }
+
     /**
      * Constructor used for creating actual per-call instances.
      */
@@ -243,17 +251,19 @@ protected DeserializationContext(DeserializationContext src,
     }
 
     /**
-     * Copy-constructor for use with <code>copy()</code> by {@link ObjectMapper#copy()}
+     * Copy-constructor for use with <code>copy()</code> by {@link ObjectMapper#copy()}.
+     * Only called on blueprint objects.
      */
     protected DeserializationContext(DeserializationContext src) {
-        _cache = new DeserializerCache();
+        _cache = src._cache.emptyCopy();
         _factory = src._factory;
 
         _config = src._config;
         _featureFlags = src._featureFlags;
         _readCapabilities = src._readCapabilities;
         _view = src._view;
-        _injectableValues = null;
+        _injectableValues = src._injectableValues;
+        _attributes = null;
     }
 
     /*

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

@@ -2282,6 +2282,7 @@ public ObjectMapper setCacheProvider(CacheProvider cacheProvider) {
         _assertNotNull("cacheProvider", cacheProvider);
         _deserializationConfig = _deserializationConfig.with(cacheProvider);
         _serializationConfig = _serializationConfig.with(cacheProvider);
+        _deserializationContext = _deserializationContext.withCaches(cacheProvider);
         return this;
     }
 

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

@@ -1,5 +1,11 @@
 package com.fasterxml.jackson.databind.cfg;
 
+import com.fasterxml.jackson.databind.DeserializationConfig;
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.deser.DeserializerCache;
+import com.fasterxml.jackson.databind.util.LookupCache;
+
 /**
  * Interface that defines API Jackson uses for constructing various internal
  * caches. This allows configuring custom caches and cache configurations.
@@ -11,5 +17,11 @@
 public interface CacheProvider
     extends java.io.Serializable
 {
-    // !!! TODO: add methods
+    /**
+     * Method to provide a {@link LookupCache} instance for constructing {@link DeserializerCache}.
+     *
+     * @return {@link LookupCache} instance for constructing {@link DeserializerCache}.
+     */
+    LookupCache<JavaType, JsonDeserializer<Object>> forDeserializerCache(DeserializationConfig config);
+
 }

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

@@ -1,19 +1,142 @@
 package com.fasterxml.jackson.databind.cfg;
 
+import com.fasterxml.jackson.databind.DeserializationConfig;
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.deser.DeserializerCache;
+import com.fasterxml.jackson.databind.util.LRUMap;
+import com.fasterxml.jackson.databind.util.LookupCache;
+
 /**
- * Default implementation of {@link CacheProvider}.
- * 
+ * The default implementation of {@link CacheProvider}.
+ * Configuration is builder-based via {@link DefaultCacheProvider.Builder}.
+ * <p>
+ * Users can either use this class or create their own {@link CacheProvider} implementation.
+ *
  * @since 2.16
  */
 public class DefaultCacheProvider
     implements CacheProvider
 {
     private static final long serialVersionUID = 1L;
 
-    public static DefaultCacheProvider defaultInstance() {
-        return new DefaultCacheProvider();
-    }
+    private final static DefaultCacheProvider DEFAULT
+        = new DefaultCacheProvider(DeserializerCache.DEFAULT_MAX_CACHE_SIZE);
+
+    /**
+     * Maximum size of the {@link LookupCache} instance constructed by {@link #forDeserializerCache(DeserializationConfig)}.
+     *
+     * @see Builder#maxDeserializerCacheSize(int)
+     */
+    protected final int _maxDeserializerCacheSize;
 
-    // To implement!
+    /*
+    /**********************************************************************
+    /* Life cycle
+    /**********************************************************************
+     */
+
+    protected DefaultCacheProvider(int deserializerCache)
+    {
+        _maxDeserializerCacheSize = deserializerCache;
+    }
+
+    /*
+    /**********************************************************************
+    /* Defaults
+    /**********************************************************************
+     */
+
+    /**
+     * @return Default {@link DefaultCacheProvider} instance using default configuration values.
+     */
+    public static CacheProvider defaultInstance() {
+        return DEFAULT;
+    }
+
+    /*
+    /**********************************************************
+    /* API implementation
+    /**********************************************************
+     */
+
+    /**
+     * Method to provide a {@link LookupCache} instance for constructing {@link DeserializerCache}.
+     * Implementation should match {@link DeserializerCache#DeserializerCache(int)}.
+     *
+     * @return {@link LookupCache} instance for constructing {@link DeserializerCache}.
+     */
+    @Override
+    public LookupCache<JavaType, JsonDeserializer<Object>> forDeserializerCache(DeserializationConfig config) {
+        return _buildCache(_maxDeserializerCacheSize);
+    }
 
+    /*
+    /**********************************************************
+    /* Overridable factory methods
+    /**********************************************************
+     */
+
+    protected <K,V> LookupCache<K,V> _buildCache(int maxSize)
+    {
+        // Use 1/4 of maximum size (but at most 64) for initial size
+        final int initialSize = Math.min(64, maxSize >> 2);
+        return new LRUMap<>(initialSize, maxSize);
+    }
+
+    /*
+    /**********************************************************
+    /* Builder Config
+    /**********************************************************
+     */
+
+    /**
+     * @return {@link Builder} instance for configuration.
+     */
+    public static DefaultCacheProvider.Builder builder() {
+        return new Builder();
+    }
+
+    /**
+     * Builder offering fluent factory methods to configure {@link DefaultCacheProvider}, keeping it immutable.
+     */
+    public static class Builder {
+
+        /**
+         * Maximum Size of the {@link LookupCache} instance created by {@link #forDeserializerCache(DeserializationConfig)}.
+         * Corresponds to {@link DefaultCacheProvider#_maxDeserializerCacheSize}.
+         */
+        private int _maxDeserializerCacheSize;
+
+        Builder() { }
+
+        /**
+         * Define the maximum size of the {@link LookupCache} instance constructed by {@link #forDeserializerCache(DeserializationConfig)}.
+         * The cache is instantiated as:
+         * <pre>
+         *     return new LRUMap<>(Math.min(64, maxSize >> 2), maxSize);
+         * </pre>
+         *
+         * @param maxDeserializerCacheSize Size for the {@link LookupCache} to use within {@link DeserializerCache}
+         * @return this builder
+         * @throws IllegalArgumentException if {@code maxDeserializerCacheSize} is negative
+         * @since 2.16
+         */
+        public Builder maxDeserializerCacheSize(int maxDeserializerCacheSize) {
+            if (maxDeserializerCacheSize < 0) {
+                throw new IllegalArgumentException("Cannot set maxDeserializerCacheSize to a negative value");
+            }
+            _maxDeserializerCacheSize = maxDeserializerCacheSize;
+            return this;
+        }
+
+        /**
+         * Constructs a {@link DefaultCacheProvider} with the provided configuration values, using defaults where not specified.
+         *
+         * @return A {@link DefaultCacheProvider} instance with the specified configuration
+         */
+        public DefaultCacheProvider build() {
+            return new DefaultCacheProvider(_maxDeserializerCacheSize);
+        }
+    }
 }

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

@@ -11,6 +11,7 @@
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.JsonToken;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.CacheProvider;
 import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
 import com.fasterxml.jackson.databind.deser.impl.ReadableObjectId;
 import com.fasterxml.jackson.databind.deser.impl.ReadableObjectId.Referring;
@@ -62,6 +63,16 @@ protected DefaultDeserializationContext(DefaultDeserializationContext src,
     }
 
     /**
+     * @since 2.16
+     */
+    protected DefaultDeserializationContext(DefaultDeserializationContext src,
+            DeserializerCache cache) {
+        super(src, cache);
+    }
+
+    /**
+     * Copy-constructor
+     *
      * @since 2.4.4
      */
     protected DefaultDeserializationContext(DefaultDeserializationContext src) {
@@ -296,6 +307,13 @@ public final KeyDeserializer keyDeserializerInstance(Annotated ann, Object deser
      */
     public abstract DefaultDeserializationContext with(DeserializerFactory factory);
 
+    /**
+     * Fluent factory method used for constructing a new instance with cache instances provided by {@link CacheProvider}.
+     * 
+     * @since 2.16
+     */
+    public abstract DefaultDeserializationContext withCaches(CacheProvider cacheProvider);
+
     /**
      * Method called to create actual usable per-deserialization
      * context instance.
@@ -384,7 +402,9 @@ public final static class Impl extends DefaultDeserializationContext
          * {@link DeserializerCache}, given factory.
          */
         public Impl(DeserializerFactory df) {
-            super(df, null);
+            // 04-Sep-2023, tatu: Not ideal (wrt not going via CacheProvider) but
+            //     has to do for backwards compatibility:
+            super(df, new DeserializerCache());
         }
 
         private Impl(Impl src,
@@ -402,6 +422,13 @@ private Impl(Impl src, DeserializationConfig config) {
             super(src, config);
         }
 
+        /**
+         * @since 2.16
+         */
+        private Impl(Impl src, DeserializerCache deserializerCache) {
+            super(src, deserializerCache);
+        }
+
         @Override
         public DefaultDeserializationContext copy() {
             ClassUtil.verifyMustOverride(Impl.class, this, "copy");
@@ -424,5 +451,11 @@ public DefaultDeserializationContext createDummyInstance(DeserializationConfig c
         public DefaultDeserializationContext with(DeserializerFactory factory) {
             return new Impl(this, factory);
         }
+
+        @Override // Since 2.16
+        public DefaultDeserializationContext withCaches(CacheProvider cacheProvider) {
+            return new Impl(this,
+                    new DeserializerCache(cacheProvider.forDeserializerCache(_config)));
+        }
     }
 }

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

@@ -73,6 +73,13 @@ public DeserializerCache(LookupCache<JavaType, JsonDeserializer<Object>> cache)
         _cachedDeserializers = cache;
     }
 
+    /**
+     * @since 2.16
+     */
+    public DeserializerCache emptyCopy() {
+        return new DeserializerCache(_cachedDeserializers.emptyCopy());
+    }
+
     /*
     /**********************************************************
     /* JDK serialization handling