1. ??? ? ????

Serialization : ??? ?????. ?? ????? ??? ??? ????? ?? ???? ??? ????(???? ??) ? ???? Java ?? ??????. ? ????? ????? ?? ????? ??? ??? ??? ????? ???? ????? ?????.

即將對象轉(zhuǎn)化為二進制，用于保存，或者網(wǎng)絡(luò)傳輸。

????: ??? ??? ?? ??? ?? ???? ??? ?? ???? Java ?? ??? ???? ???????. ?, ??? ???? ??? ???? ???? ??? ??? ??? ???? ??

與序列化相反，將二進制轉(zhuǎn)化成對象。

2. ???? ??

#?? ??#① ???? ?? ??? ???? ??????? ???? ?? ?

② ??? ???? ????? ?? ??? ???? ?? ?; RMI? ?? ??? ???? ??

一些應(yīng)用場景，涉及到將對象轉(zhuǎn)化成二進制，序列化保證了能夠成功讀取到保存的對象。

3.Java ??? ??

?? ???? ????? ?? ???? ??? ???? ????. ??? ?? ?????

IO ???? ?? ???? ???? ??? ??? ???? ??? ??? ??? ?? ?? ? ????.

?? ??? ???? ??? ?? ?????? ?????:

import java.io.Serializable;
public class User implements Serializable{
    private static final long serialVersionUID = 1L;
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }
}

?? ???? ???? ??? ???? ?? ?? ?? ???? ?????:

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
public class SerializeUtil {
    // 保存對象，序列化
    public static void saveObject(Object object) throws Exception {
        ObjectOutputStream out = null;
        FileOutputStream fout = null;
        try {
            fout = new FileOutputStream("D:/1.txt");
            out = new ObjectOutputStream(fout);
            out.writeObject(object);
        } finally {
            fout.close();
            out.close();
        }
    }
    // 讀取對象，反序列化
    public static Object readObject() throws Exception {
        ObjectInputStream in = null;
        FileInputStream fin = null;
        try {
            fin = new FileInputStream("D:/1.txt");
            in = new ObjectInputStream(fin);
            Object object = in.readObject();
            return object;
        } finally {
            fin.close();
            in.close();
        }
    }
}

#???? # ???:

public class Main {
    public static void main(String[] args) {
        User user = new User();
        user.setName("旭旭寶寶");
        user.setAge(33);
        // 保存
        try {
            SerializeUtil.saveObject(user);
        } catch (Exception e) {
            System.out.println("保存時異常：" + e.getMessage());
        }
        // 讀取
        User userObject;
        try {
            userObject = (User) SerializeUtil.readObject();
            System.out.println(userObject);
        } catch (Exception e) {
            System.out.println("讀取時異常：" + e.getMessage());
        }
    }
}

??? ??:

??? ??? ??? ????? ??? ?? ?? ?????. ?? ??? ?????? ???? ??? ??? ?????. Serialiable ????? ??? ??? ?????:

public class User {
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }
}

?? ?? Main ???? ??????:

??? ? ? ????. ?? ??? ?????. ?? e.printStackTrace()? ???? ?? ?? ??? ?????.

????? ?? ???? ? ?? ? ? ?? ?????.

4. ??? ID? ??

????? ???? ? serialVersionUID ??? ?????. ??? ID

private static final long serialVersionUID = 1L;

? ??? ID? ???? ?? ??? ???? ?? ??? ???! Java? ??? ????? ??? ???? serialVersionUID? ???? ?? ???? ?????. JVM? ?? ??? ???? serialVersionUID? ?? ??? ???? serialVersionUID? ?????. ??? ??? ???? ?? ???? ??? ??? ?????.

即序列化ID是為了保證成功進行反序列化

5. ?? ??? ID

"serialVersionUID"?? ??? ???? ????? ???? ?? ??, long ??? ??? ?? ?? Java ??? ????? ??? ?? ??? ???? ???? ???? serialVersionUID? ???? ?????. ? ?? ??? ??? ???? ??? serialVersionUID? ?????. ?? ?? ???? ??? ? ??? ??? ?? ?? ?? ???? ?? ?? ???? ?? ??? ???? ???. ?? deserialization ?? serialVersionUID? ???? ?? deserialization? ???? ???. ???? ??? ???? ???? ?? ???? "serialVersionUID" ??? ????? ?? ?? ???? ?? ??? ? ????? ??? ? ????.

如果沒有顯示指定serialVersionUID，會自動生成一個。
只有同一次編譯生成的class才會生成相同的serialVersionUID。
但是如果出現(xiàn)需求變動，Bean類發(fā)生改變，則會導(dǎo)致反序列化失敗。為了不出現(xiàn)這類的問題，所以我們最好還是顯式的指定一個
serialVersionUID。

6. ??? ?? ?? ??

1 ?? ??? ????? ????(??, ???) #?? ??#2. ?? ???? ???? ???? ?? ???? ??? ?? ?????? ????? ???? ??? ???? ???? ?????.

3. ??? ???? ??? ?? ??? ???? ?? ?? ??? ????? ???? ??? ??????.

子類序列化時：
如果父類沒有實現(xiàn)Serializable接口，沒有提供默認構(gòu)造函數(shù)，那么子類的序列化會出錯；
如果父類沒有實現(xiàn)Serializable接口，提供了默認的構(gòu)造函數(shù)，那么子類可以序列化，父類的成員變量不會被序列化。如果父類
實現(xiàn)了Serializable接口，則父類和子類都可以序列化。

7. ?? ???? ??? ????? ??—Protostuff

?? Java? ?? ??? ??? ??? ??? ?????)? ?? ????? ????. github?? ??? ???? ???? ????? ????: https://github.com/eihay/jvm-serializers/wiki

?? ??? ?? ?? Google?? ??? Colfer???. ??? Colfer? ????? ?? ??? ??? ??? Protostuff ??? ?????? ?????. ?????? ????? ? ?? ?????(?? ? ???)? ????? ???.

①github ??: https://github.com/protostuff/protostuff

3Maven? ???? ?? ??? ??:

<dependency>
  <groupId>io.protostuff</groupId>
  <artifactId>protostuff-core</artifactId>
  <version>1.5.9</version>
</dependency>

<dependency>
  <groupId>io.protostuff</groupId>
  <artifactId>protostuff-core</artifactId>
  <version>1.5.9</version>
</dependency>

?? ?? ??

import com.dyuproject.protostuff.LinkedBuffer;
import com.dyuproject.protostuff.ProtobufIOUtil;
import com.dyuproject.protostuff.ProtostuffIOUtil;
import com.dyuproject.protostuff.Schema;
import com.dyuproject.protostuff.runtime.RuntimeSchema;
public class Main {
    public static void main(String[] args) {
        User user = new User();
        user.setName("旭旭寶寶");
        user.setAge(33);
        Schema<User> schema = RuntimeSchema.getSchema(User.class);
        // 保存對象，序列化，轉(zhuǎn)化二進制數(shù)據(jù)
        LinkedBuffer buffer = LinkedBuffer.allocate(512);
        final byte[] protostuff;
        try {
            protostuff = ProtobufIOUtil.toByteArray(user, schema, buffer);
        } finally {
            buffer.clear();
        }
        // 讀取對象，反序列化
        User userObject = schema.newMessage();
        ProtostuffIOUtil.mergeFrom(protostuff, userObject, schema);
        System.out.println(userObject);
    }
}

??? ???? ??? ?? ?????? ???? ????

public class User {
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }
}

??? ??:

若要要整合Redis使用，也可以寫成一個工具類：

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import com.dyuproject.protostuff.LinkedBuffer;
import com.dyuproject.protostuff.ProtobufIOUtil;
import com.dyuproject.protostuff.Schema;
import com.dyuproject.protostuff.runtime.RuntimeSchema;
public class SerializeUtil {
    private static Map<Class<?>, Schema<?>> cachedSchema = new ConcurrentHashMap<>();
    @SuppressWarnings("unchecked")
    public static <T> byte[] serializer(T obj) {
        Class<T> clazz = (Class<T>) obj.getClass();
        Schema<T> schema = getSchema(clazz);
        return ProtobufIOUtil.toByteArray(obj, schema, LinkedBuffer.allocate(256));
    }
    public static <T> T deSerializer(byte[] bytes, Class<T> clazz) {
        T message;
        try {
            message = clazz.newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            throw new RuntimeException(e);
        }
        Schema<T> schema = getSchema(clazz);
        ProtobufIOUtil.mergeFrom(bytes, message, schema);
        return message;
    }
    @SuppressWarnings("unchecked")
    public static <T> Schema<T> getSchema(Class<T> clazz) {
        Schema<T> schema = (Schema<T>) cachedSchema.get(clazz);
        if (schema == null) {
            schema = RuntimeSchema.createFrom(clazz);
            if (schema != null) {
                cachedSchema.put(clazz, schema);
            }
        }
        return schema;
    }
}

這樣即使我們的User類就不用再實現(xiàn)Serialiable接口了，同樣可以進行序列化，效率也更高。

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