探险新型序列化工具MessagePack

MessagePack是最近一个比较热门与Json做比较的序列化工具，它的优点是相比于json，序列化速度更快和序列化之后的字节数组更小，正如它的官网https://msgpack.org/卖的广告所说

It’s like JSON.
but fast and small.

下面我们以三个方面来对MessagePack做一个初步的探险

一.What is MessagePack

1.以官网的阐述来表明：

MessagePack is an efficient binary serialization format. It lets you exchange data among multiple languages like JSON. But it’s faster and smaller. Small integers are encoded into a single byte, and typical short strings require only one extra byte in addition to the strings themselves.
中文翻译：
MessagePack是一种有效的二进制序列化格式。它允许您在多种语言（如JSON）之间交换数据。但它更快更小。小整数被编码为单个字节，典型的短字符串除了字符串本身外只需要一个额外的字节。

可以看出它序列化出来能比json更小的原因是，整数会被编码成一个字节，另外json的字符串的冒号和引号也会被以一种特殊的方式进行压缩，下面的图片可以看出来MessagePack压缩之后的效果：
这里写图片描述
from:http://indiegamr.com/cut-your-data-exchange-traffic-by-up-to-50-with-one-line-of-code-msgpack-vs-json/

2.验证Message的序列化速度和内容是否更优于JSON

package msgpack;

import com.alibaba.fastjson.JSON;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.msgpack.jackson.dataformat.MessagePackFactory;

import java.io.IOException;

public class MsgPackMain {
    public static void main(String[] args) throws IOException {
        Person person = new Person("andrew", "24", "man");
        //fastjson
        long jsonStartTime = System.currentTimeMillis();
        String jsonStr = JSON.toJSONString(person);
        System.out.println("json花费时间:" + (System.currentTimeMillis() - jsonStartTime));
        System.out.println("json byteArr size is" + jsonStr.getBytes("UTF-8").length);

        //msgPack use jackson
        ObjectMapper objectMapper = new ObjectMapper(new MessagePackFactory());
        long msgPackStartTime = System.currentTimeMillis();
        byte[] msgPackByteArr = objectMapper.writeValueAsBytes(person);
        System.out.println("msgPack花费时间:" + (System.currentTimeMillis() - msgPackStartTime));
        System.out.println("msgPack byteArr size is :" + msgPackByteArr.length);
    }
}

测试结果：

json花费时间:199
json byteArr size is40
msgPack花费时间:72
msgPack byteArr size is :28

从测试结果可以看出msgPack明显在速度和size方面都远胜于json，而且由于有jackson的依赖库，所以使用和替换jackson-json都非常简单

二.How to use

下面我们来做一些简单的demo：
引入需要依赖的maven库:

 <dependency>
      <groupId>org.msgpack</groupId>
      <artifactId>jackson-dataformat-msgpack</artifactId>
      <version>${msgpack.version}</version>
</dependency>

jackson包装的msgPack，使用非常简单，下面来封装简单的MsgPackUtil

package msgpack;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.msgpack.jackson.dataformat.MessagePackFactory;

import java.io.IOException;
import java.util.List;
import java.util.Map;

public class MsgPackUtil {

    private static final ObjectMapper objectMapper = new ObjectMapper(new MessagePackFactory());

    public static <T> T readObj(byte[] byteArr, Class<T> clazz) throws IOException {
        return objectMapper.readValue(byteArr, clazz);
    }

    public static <T> byte[] writeObj(T t) throws JsonProcessingException {
        return objectMapper.writeValueAsBytes(t);
    }

    public static <T> List<T> readList(byte[] listByteArr, TypeReference<List<T>> typeReference) throws IOException {
        return objectMapper.readValue(listByteArr, typeReference);
    }

    public static <T,V> Map<T, V> readMap(byte[] mapByteArr, TypeReference<Map<T, V>> typeReference) throws IOException {
        return objectMapper.readValue(mapByteArr, typeReference);
    }
}

demo代码:

private static void msgPackJackSonDemo() throws IOException {
        //Object
        Person person = new Person("andrew", "24", "man");
        byte[] personByteArr = MsgPackUtil.writeObj(person);
        System.out.println("ObjByteArr size is :" + personByteArr.length);
        //使用readValue时候，需要空的构造方法
        System.out.println(MsgPackUtil.readObj(personByteArr, Person.class));

        //list
        List<String> testList = new ArrayList<>(3);
        testList.add("hello");
        testList.add("msgPack");
        testList.add("java");
        byte[] listByteArr = MsgPackUtil.writeObj(testList);
        System.out.println("listByteArr size is :" + listByteArr.length);
        //readList只支持POJO和基本类型List
        System.out.println(JSON.toJSONString(MsgPackUtil.readList(listByteArr, new TypeReference<List<String>>() {})));

        //map
        Map<String, String> testMap = new HashMap<>(3);
        testMap.put("hello", "hello");
        testMap.put("msgPack", "msgPack");
        testMap.put("java", "java");
        byte[] mapByteArr = MsgPackUtil.writeObj(testMap);
        System.out.println("mapByteArr size is :" + mapByteArr.length);
        System.out.println(JSON.toJSONString(MsgPackUtil.readMap(mapByteArr, new TypeReference<Map<String, String>>() {})));
    }

三.使用场景

1.适用于将数据存储在类似于mc和redis这类的nosql数据库中，因为数据可以序列化的更小更快，那么在网络上的传输消耗会减少，同时存在redis里面的内存占用也会减少。
2.适用于分布式框架里面多机之间的网络传输，生产上的实现：fluentd https://github.com/fluent/fluentd
3.适用于前后端数据的交互，当前后端完全分离之后，后端可以使用MsgPack代替json以获取更快的速度

                                                                                written by 黄文岳
                                                                                2018.09.02