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General data-binding functionality for Jackson: works on core streaming API
There is a newer version: 2.18.1
package com.fasterxml.jackson.databind.ser;

import java.util.concurrent.atomic.AtomicReference;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.ser.impl.ReadOnlyClassToSerializerMap;
import com.fasterxml.jackson.databind.util.LRUMap;
import com.fasterxml.jackson.databind.util.TypeKey;

/**
 * Simple cache object that allows for doing 2-level lookups: first level is
 * by "local" read-only lookup Map (used without locking)
 * and second backup level is by a shared modifiable HashMap.
 * The idea is that after a while, most serializers are found from the
 * local Map (to optimize performance, reduce lock contention),
 * but that during buildup we can use a shared map to reduce both
 * number of distinct read-only maps constructed, and number of
 * serializers constructed.
 *
 * Cache contains three kinds of entries,
 * based on combination of class pair key. First class in key is for the
 * type to serialize, and second one is type used for determining how
 * to resolve value type. One (but not both) of entries can be null.
 */
public final class SerializerCache
{
    /**
     * By default, allow caching of up to 4000 serializer entries (for possibly up to
     * 1000 types; but depending access patterns may be as few as half of that).
     */
    public final static int DEFAULT_MAX_CACHED = 4000;

    /**
     * Shared, modifiable map; all access needs to be through synchronized blocks.
     *

     * NOTE: keys are of various types (see below for key types), in addition to
     * basic {@link JavaType} used for "untyped" serializers.
     */
    private final LRUMap> _sharedMap;

    /**
     * Most recent read-only instance, created from _sharedMap, if any.
     */
    private final AtomicReference _readOnlyMap;

    public SerializerCache() {
        this(DEFAULT_MAX_CACHED);
    }

    public SerializerCache(int maxCached) {
        int initial = Math.min(64, maxCached>>2);
        _sharedMap = new LRUMap>(initial, maxCached);
        _readOnlyMap = new AtomicReference();
    }

    /**
     * Method that can be called to get a read-only instance populated from the
     * most recent version of the shared lookup Map.
     */
    public ReadOnlyClassToSerializerMap getReadOnlyLookupMap()
    {
        ReadOnlyClassToSerializerMap m = _readOnlyMap.get();
        if (m != null) {
            return m;
        }
        return _makeReadOnlyLookupMap();
    }

    private final synchronized ReadOnlyClassToSerializerMap _makeReadOnlyLookupMap() {
        // double-locking; safe, but is it really needed? Not doing that is only a perf problem,
        // not correctness
        ReadOnlyClassToSerializerMap m = _readOnlyMap.get();
        if (m == null) {
            m = ReadOnlyClassToSerializerMap.from(_sharedMap);
            _readOnlyMap.set(m);
        }
        return m;
    }

    /*
    /**********************************************************
    /* Lookup methods for accessing shared (slow) cache
    /**********************************************************
     */

    public synchronized int size() {
        return _sharedMap.size();
    }

    /**
     * Method that checks if the shared (and hence, synchronized) lookup Map might have
     * untyped serializer for given type.
     */
    public JsonSerializer