自定义序列化

当我们要决定控制哪些Field方法被序列化时，有两种方法：

• 让序列化类实现其Serializable接口时，重写writeObject()方法来负责写入需要序列化的Field，并重写其相对应的readObject()方法来恢复序列化的Field。
• 让序列化类实现Externalizable接口，采用上述那点思路实现其readExternal(),writeExternal()两个方法。(性能略高)
  代码例子：
  第一种：

public class Person implements java.io.Serializable {
    private String name;
    private int age;
    // 注意此处没有提供无参数的构造器!
    public Person(String name , int age)
    {
        System.out.println("有参数的构造器");
        this.name = name;
        this.age = age;
    }
    // name的setter和getter方法
    public void setName(String name)
    {
        this.name = name;
    }
    public String getName()
    {
        return this.name;
    }
    // age的setter和getter方法
    public void setAge(int age)
    {
        this.age = age;
    }
    public int getAge()
    {
        return this.age;
    }

    private void writeObject(java.io.ObjectOutputStream out)
        throws IOException
    {
        // 将name Field的值反转后写入二进制流
        out.writeObject(new StringBuffer(name).reverse());
        out.writeInt(age);
    }
    private void readObject(java.io.ObjectInputStream in)
        throws IOException, ClassNotFoundException
    {
        // 将读取的字符串反转后赋给name Field
        this.name = ((StringBuffer)in.readObject()).reverse()
            .toString();
        this.age = in.readInt();
    }
}

第二种：

public class Person implements java.io.Externalizable {
    private String name;
    private int age;
    // 注意此处没有提供无参数的构造器!
    public Person(String name , int age)
    {
        System.out.println("有参数的构造器");
        this.name = name;
        this.age = age;
    }
    // name的setter和getter方法
    public void setName(String name)
    {
        this.name = name;
    }
    public String getName()
    {
        return this.name;
    }

    // age的setter和getter方法
    public void setAge(int age)
    {
        this.age = age;
    }
    public int getAge()
    {
        return this.age;
    }

    public void writeExternal(java.io.ObjectOutput out)
        throws IOException
    {
        // 将name Field的值反转后写入二进制流
        out.writeObject(new StringBuffer(name).reverse());
        out.writeInt(age);
    }
    public void readExternal(java.io.ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        // 将读取的字符串反转后赋给name Field
        this.name = ((StringBuffer)in.readObject()).reverse().toString();
        this.age = in.readInt();
    }
}