feat: allow clearing all caches (#4954)

Author: jin-harmoney

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

@@ -707,6 +707,19 @@ public final KeyDeserializer findKeyDeserializer(JavaType keyType,
         return kd;
     }
 
+    /**
+     * Method that will drop all dynamically constructed deserializers (ones that
+     * are counted as result value for {@link DeserializerCache#cachedDeserializersCount}).
+     * This can be used to remove memory usage (in case some deserializers are
+     * only used once or so), or to force re-construction of deserializers after
+     * configuration changes for mapper than owns the provider.
+
+     * @since 2.19
+     */
+    public void flushCachedDeserializers() {
+        _cache.flushCachedDeserializers();
+    }
+
     /*
     /**********************************************************
     /* Public API, ObjectId handling

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

@@ -4789,6 +4789,26 @@ public void acceptJsonFormatVisitor(JavaType type, JsonFormatVisitorWrapper visi
         _serializerProvider(getSerializationConfig()).acceptJsonFormatVisitor(type, visitor);
     }
 
+    /*
+    /**********************************************************
+    /* Extended Public API: caches
+    /**********************************************************
+     */
+
+    /**
+     * Method that will clear all caches.
+     * This can be used to remove memory usage or to force re-construction cached entries after configuration changes.
+     * Can also be used to avoid class-loader memory leaks when reloading applications.
+
+     * @since 2.19
+     */
+    public void clearCaches() {
+        _rootDeserializers.clear();
+        getTypeFactory().clearCache();
+        getDeserializationContext().flushCachedDeserializers();
+        getSerializerProvider().flushCachedSerializers();
+    }
+
     /*
     /**********************************************************
     /* Internal factory methods for type ids, overridable

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

@@ -1280,6 +1280,24 @@ public final void defaultSerializeNull(JsonGenerator gen) throws IOException
         }
     }
 
+    /*
+    /********************************************************
+    /* Cache manipulation
+    /********************************************************
+     */
+
+    /**
+     * Method that will drop all serializers currently cached by this provider.
+     * This can be used to remove memory usage (in case some serializers are
+     * only used once or so), or to force re-construction of serializers after
+     * configuration changes for mapper than owns the provider.
+
+     * @since 2.19
+     */
+    public void flushCachedSerializers() {
+        _serializerCache.flush();
+    }
+
     /*
     /********************************************************
     /* Error reporting

src/main/java/com/fasterxml/jackson/databind/ser/DefaultSerializerProvider.java

@@ -553,16 +553,6 @@ public int cachedSerializersCount() {
         return _serializerCache.size();
     }
 
-    /**
-     * Method that will drop all serializers currently cached by this provider.
-     * This can be used to remove memory usage (in case some serializers are
-     * only used once or so), or to force re-construction of serializers after
-     * configuration changes for mapper than owns the provider.
-     */
-    public void flushCachedSerializers() {
-        _serializerCache.flush();
-    }
-
     /*
     /**********************************************************
     /* Extended API called by ObjectMapper: other

src/test/java/com/fasterxml/jackson/databind/ObjectMapperTest.java

@@ -409,6 +409,30 @@ public void testProviderConfig() throws Exception
         assertEquals(4, m._deserializationContext._cache.cachedDeserializersCount());
     }
 
+    @Test
+    public void testClearCaches() throws Exception
+    {
+        ObjectMapper m = new ObjectMapper();
+
+        // Serialize and deserialize to fill caches
+        final String JSON = "{ \"x\" : 3 }";
+        Bean bean = m.readValue(JSON, Bean.class);
+        m.writeValueAsString("test");
+
+        // Caches should not be empty
+        assertNotEquals(0, m._deserializationContext._cache.cachedDeserializersCount());
+        assertNotEquals(0, m._rootDeserializers.size());
+        assertNotEquals(0, m._serializerProvider.cachedSerializersCount());
+
+        // Clear caches
+        m.clearCaches();
+
+        // Caches should be empty
+        assertEquals(0, m._deserializationContext._cache.cachedDeserializersCount());
+        assertEquals(0, m._rootDeserializers.size());
+        assertEquals(0, m._serializerProvider.cachedSerializersCount());
+    }
+
     // For [databind#689]
     @Test
     public void testCustomDefaultPrettyPrinter() throws Exception