java - 为什么java内置序列化比Gson差？

Question

我认为Java内置序列化的性能应该不错。和Gson相比，它不需要做词法分析，应该比Gson快。

但在我的测试中，结果却恰恰相反。看我的代码:

package cleancode;

import com.google.gson.Gson;

import java.io.*;

public class SerializationPerformanceTest {

    public static final int MAX_LOOP = 1000000;

    public static void main(String[] args) throws Exception {
        trySerialization();
        tryGson();
    }

    private static void tryGson() {
        long start = System.currentTimeMillis();
        Gson gson = new Gson();
        for (int i = 0; i < MAX_LOOP; i++) {
            String json = gson.toJson(createUser());
            gson.fromJson(json, User.class);
        }
        long end = System.currentTimeMillis();
        System.out.println("Gson cost: " + (end - start) + "ms");
    }

    private static void trySerialization() throws IOException, ClassNotFoundException {
        long start = System.currentTimeMillis();
        for (int i = 0; i < MAX_LOOP; i++) {
            ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
            ObjectOutputStream stream = new ObjectOutputStream(byteStream);
            stream.writeObject(createUser());
            byte[] binary = byteStream.toByteArray();

            ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(binary);
            ObjectInputStream input = new ObjectInputStream(byteArrayInputStream);
            input.readObject();
        }
        long end = System.currentTimeMillis();
        System.out.println("Serialization cost: " + (end - start) + "ms");
    }

    private static User createUser() {
        User user = new User();
        user.setAaa(newValue());
        user.setBbb(newValue());
        user.setCcc(newValue());
        user.setDdd(newValue());
        user.setEee(newValue());
        user.setFff(newValue());
        user.setGgg(newValue());
        return user;
    }

    private static String newValue() {
        return "" + System.currentTimeMillis();
    }
}

类User是一个java bean:

class User implements Serializable {
    private String aaa;
    private String bbb;
    private String ccc;
    private String ddd;
    private String eee;
    private String fff;
    private String ggg;

    String getAaa() {
        return aaa;
    }

    void setAaa(String aaa) {
        this.aaa = aaa;
    }

    String getBbb() {
        return bbb;
    }

    void setBbb(String bbb) {
        this.bbb = bbb;
    }

    String getCcc() {
        return ccc;
    }

    void setCcc(String ccc) {
        this.ccc = ccc;
    }

    String getDdd() {
        return ddd;
    }

    void setDdd(String ddd) {
        this.ddd = ddd;
    }

    String getEee() {
        return eee;
    }

    void setEee(String eee) {
        this.eee = eee;
    }

    String getFff() {
        return fff;
    }

    void setFff(String fff) {
        this.fff = fff;
    }

    String getGgg() {
        return ggg;
    }

    void setGgg(String ggg) {
        this.ggg = ggg;
    }
}

我电脑上的结果:

Serialization cost: 12339ms
Gson cost: 3971ms

Gson 版本比“序列化”版本快得多。为什么？!

我的测试代码有什么问题吗，或者Java内置序列化实际上很慢？

Answer 1

Java 内置序列化非常慢。供引用:https://github.com/eishay/jvm-serializers/wiki

但是，有quite a few ways in which your benchmark should be improved for more-accurate results.