一招MAX降低10倍，现在它是我的了| 京东零售技术团队

<!--OHC相关-->
<dependency>
	<groupId>org.caffinitas.ohc</groupId>
	<artifactId>ohc-core</artifactId>
	<version>0.7.4</version>
</dependency>

<!--OHC 存储的是二进制数组，所以需要实现OHC序列化接口，将缓存数据与二进制数组之间序列化和反序列化-->
<!--这里使用的是protostuff，当然也可以使用kryo、Hession等，通过压测验证选择适合的-->
<dependency>
	<groupId>io.protostuff</groupId>
	<artifactId>protostuff-core</artifactId>
	<version>1.6.0</version>
</dependency>
<dependency>
	<groupId>io.protostuff</groupId>
	<artifactId>protostuff-runtime</artifactId>
	<version>1.6.0</version>
</dependency>

OHCache<String, XxxxInfo> basicStoreInfoCache = OHCacheBuilder.<String, XxxxInfo>newBuilder()
                    .keySerializer(new OhcStringSerializer()) //key的序列化器
                    .valueSerializer(new OhcProtostuffXxxxInfoSerializer()) //value的序列化器
                    .segmentCount(512) // 分段数量 默认=2*CPU核数
                    .hashTableSize(100000)// 哈希表大小 默认=8192
                    .capacity(1024 * 1024 * 1024) //缓存容量 单位B 默认64MB
                    .eviction(Eviction.LRU) // 淘汰策略 可选LRU\W_TINY_LFU\NONE
                    .timeouts(false) //不使用过期时间，根据业务自己选择
                    .build();

//key-String 序列化器，这里直接复用OCH源码中测试用例的String序列化器
public class OhcStringSerializer implements CacheSerializer<String> {

    @Override
    public int serializedSize(String value) {
        return writeUTFLen(value);
    }

    @Override
    public void serialize(String value, ByteBuffer buf) {
        // 得到字符串对象UTF-8编码的字节数组
        byte[] bytes = value.getBytes(Charsets.UTF_8);
        buf.put((byte) ((bytes.length >>> 8) & 0xFF));
        buf.put((byte) ((bytes.length >>> 0) & 0xFF));
        buf.put(bytes);
    }


    @Override
    public String deserialize(ByteBuffer buf) {
        int length = (((buf.get() & 0xff) << 8) + ((buf.get() & 0xff) << 0));
        byte[] bytes = new byte[length];
        buf.get(bytes);
        return new String(bytes, Charsets.UTF_8);
    }
    static int writeUTFLen(String str) {
        int strlen = str.length();
        int utflen = 0;
        int c;

        for (int i = 0; i < strlen; i++) {
            c = str.charAt(i);
            if ((c >= 0x0001) && (c <= 0x007F)){
                utflen++;}
            else if (c > 0x07FF){
                utflen += 3;}
            else{
                utflen += 2;
            }
        }

        if (utflen > 65535) {
            throw new RuntimeException("encoded string too long: " + utflen + " bytes");
        }
        return utflen + 2;
    }
}


//value-自定义对象序列化器，这里用Protostuff实现,可以自己选择使用kryo、Hession等实现
public class OhcProtostuffXxxxInfoSerializer implements CacheSerializer<XxxxInfo> {

    /**
     * 将缓存数据序列化到 ByteBuffer 中，ByteBuffer是OHC管理的堆外内存区域的映射。
     */
    @Override
    public void serialize(XxxxInfo t, ByteBuffer byteBuffer) {
        byteBuffer.put(ProtostuffUtils.serialize(t));
    }
    /**
     * 对堆外缓存的数据进行反序列化
     */
    @Override
    public XxxxInfo deserialize(ByteBuffer byteBuffer) {
        byte[] bytes = new byte[byteBuffer.remaining()];
        byteBuffer.get(bytes);
        return ProtostuffUtils.deserialize(bytes, XxxxInfo.class);
    }

    /**
     * 计算字序列化后占用的空间
     */
    @Override
    public int serializedSize(XxxxInfo t) {
        return ProtostuffUtils.serialize(t).length;
    }
}

public class ProtostuffUtils {

    /**
     * 避免每次序列化都重新申请Buffer空间，提升性能
     */
    private static final FastThreadLocal<LinkedBuffer> bufferPool = new FastThreadLocal<LinkedBuffer>() {
        @Override
        protected LinkedBuffer initialValue() throws Exception {
            return LinkedBuffer.allocate(4 * 2 * LinkedBuffer.DEFAULT_BUFFER_SIZE);
        }
    };

    /**
     * 缓存Schema
     */
    private static Map<Class<?>, Schema<?>> schemaCache = new ConcurrentHashMap<>();

    /**
     * 序列化方法，把指定对象序列化成字节数组
     */
    @SuppressWarnings("unchecked")
    public static <T> byte[] serialize(T obj) {
        Class<T> clazz = (Class<T>) obj.getClass();
        Schema<T> schema = getSchema(clazz);
        byte[] data;
        LinkedBuffer linkedBuffer = null;
        try {
            linkedBuffer = bufferPool.get();
            data = ProtostuffIOUtil.toByteArray(obj, schema, linkedBuffer);
        } finally {
            if (Objects.nonNull(linkedBuffer)) {
                linkedBuffer.clear();
            }
        }

        return data;
    }

    /**
     * 反序列化方法，将字节数组反序列化成指定Class类型
     */
    public static <T> T deserialize(byte[] data, Class<T> clazz) {
        Schema<T> schema = getSchema(clazz);
        T obj = schema.newMessage();
        ProtostuffIOUtil.mergeFrom(data, obj, schema);
        return obj;
    }

    @SuppressWarnings("unchecked")
    private static <T> Schema<T> getSchema(Class<T> clazz) {
        Schema<T> schema = (Schema<T>) schemaCache.get(clazz);
        if (Objects.isNull(schema)) {
            schema = RuntimeSchema.getSchema(clazz);
            if (Objects.nonNull(schema)) {
                schemaCache.put(clazz, schema);
            }
        }

        return schema;
    }
}