java序列化（transient和static修饰的变量的序列化实现）

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序列化

(代码摘抄自Java编程思想)

平常序列化知识不做介绍把书里的有意思东西摘抄下来

用transient修饰是变量是否可以序列化？

静态变量是否可以初始化？

1.用 Externalizable 接口实现序列化（在重写的writeExternal和readExternal中实现序列化，）

忽视成员变量是否用 transient修饰

2.用Serializable实现序列化（

private void writeObject(ObjectOutputStream stream)

throws IOException ;

private void readObject(ObjectInputStream stream)

throws IOException, ClassNotFoundException ;

这些方法必须具有准确的特征签名）

修饰符必须为private 。（private修饰的方法如何调用的可以自行思考）

也可以忽视成员变量是否用 transient修饰

3.序列化静态变量可以在所在类实现public static void

serializeStaticState方法和deserializeStaticState方法

并且测试main函数里调用

从而实现静态变量初始化

代码如下

1.用 Externalizable 接口实现序列化

public class Blip3 implements Externalizable {
  private int i;
  private transient String s; // No initialization
  public Blip3() {
  System.out.println("Blip3 Constructor");
    // s, i not initialized
  }
  public Blip3(String x, int a) {
  System.out.println("Blip3(String x, int a)");
    s = x;
    i = a;
    // s & i initialized only in non-default constructor.
  }
  public String toString() { return s + i; }
  public void writeExternal(ObjectOutput out)
  throws IOException {
  System.out.println("Blip3.writeExternal");
    // You must do this:
    out.writeObject(s);
    out.writeInt(i);
  }
  public void readExternal(ObjectInput in)
  throws IOException, ClassNotFoundException {
  System.out.println("Blip3.readExternal");
    // You must do this:
    s = (String)in.readObject();
    i = in.readInt();
  }
  public static void main(String[] args)
  throws IOException, ClassNotFoundException {
  System.out.println("Constructing objects:");
    Blip3 b3 = new Blip3("A String ", 47);
//    Blip3 b3 = new Blip3();
    System.out.println(b3);
    ObjectOutputStream o = new ObjectOutputStream(
      new FileOutputStream("Blip3.out"));
    System.out.println("Saving object:");
    o.writeObject(b3);
    o.close();
    // Now get it back:
    ObjectInputStream in = new ObjectInputStream(
      new FileInputStream("Blip3.out"));
    System.out.println("Recovering b3:");
    b3 = (Blip3)in.readObject();
    System.out.println(b3);
  }
} /* Output:
Constructing objects:
Blip3(String x, int a)
A String 47
Saving object:
Blip3.writeExternal
Recovering b3:
Blip3 Constructor
Blip3.readExternal
A String 47
*///:~

2.用Serializable实现序列化

public class SerialCtl implements Serializable {
  private String a;
  private transient String b;
  public SerialCtl(String aa, String bb) {
    a = "Not Transient: " + aa;
    b = "Transient: " + bb;
  }
  public String toString() { return a + "\n" + b; }
  private void writeObject(ObjectOutputStream stream)
//  public void writeObject(ObjectOutputStream stream)
  throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(b);
  }
  private void readObject(ObjectInputStream stream)
//  public void readObject(ObjectInputStream stream)
  throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    b = (String)stream.readObject();
  }
  public static void main(String[] args)
  throws IOException, ClassNotFoundException {
    SerialCtl sc = new SerialCtl("Test1", "Test2");
    System.out.println("Before:\n" + sc);
    ByteArrayOutputStream buf= new ByteArrayOutputStream();
    ObjectOutputStream o = new ObjectOutputStream(buf);
    o.writeObject(sc);
    // Now get it back:
    ObjectInputStream in = new ObjectInputStream(
      new ByteArrayInputStream(buf.toByteArray()));
    SerialCtl sc2 = (SerialCtl)in.readObject();
    System.out.println("After:\n" + sc2);
  }
} /* Output:
Before:
Not Transient: Test1
Transient: Test2
After:
Not Transient: Test1
Transient: Test2
*///:~

3.1序列化静态变量(没实现静态变量序列化)

3.1_1）序列化

abstract class Shape implements Serializable {
  public static final int RED = 1, BLUE = 2, GREEN = 3;
  private int xPos, yPos, dimension;
  private static Random rand = new Random(47);
  private static int counter = 0;
  public abstract void setColor(int newColor);
  public abstract int getColor();
  public Shape(int xVal, int yVal, int dim) {
    xPos = xVal;
    yPos = yVal;
    dimension = dim;
  }
  public String toString() {
    return getClass() +
      "color[" + getColor() + "] xPos[" + xPos +
      "] yPos[" + yPos + "] dim[" + dimension + "]\n";
  }
  public static Shape randomFactory() {
    int xVal = rand.nextInt(100);
    int yVal = rand.nextInt(100);
    int dim = rand.nextInt(100);
    switch(counter++ % 3) {
      default:
      case 0: return new Circle(xVal, yVal, dim);
      case 1: return new Square(xVal, yVal, dim);
      case 2: return new Line(xVal, yVal, dim);
    }
  }
}
 
class Circle extends Shape {
  private static int color = RED;
  public Circle(int xVal, int yVal, int dim) {
    super(xVal, yVal, dim);
  }
  public void setColor(int newColor) { color = newColor; }
  public int getColor() { return color; }
}
 
class Square extends Shape {
  private static int color;
  public Square(int xVal, int yVal, int dim) {
    super(xVal, yVal, dim);
    color = RED;
  }
  public void setColor(int newColor) { color = newColor; }
  public int getColor() { return color; }
}
 
class Line extends Shape {
  private static int color = RED;
  public static void
  serializeStaticState(ObjectOutputStream os)
  throws IOException { os.writeInt(color); }
  public static void
  deserializeStaticState(ObjectInputStream os)
  throws IOException { color = os.readInt(); }
  public Line(int xVal, int yVal, int dim) {
    super(xVal, yVal, dim);
  }
  public void setColor(int newColor) { color = newColor; }
  public int getColor() { return color; }
}
 
public class StoreCADState {
  public static void main(String[] args) throws Exception {
    List<Class<? extends Shape>> shapeTypes =
      new ArrayList<Class<? extends Shape>>();
    // Add references to the class objects:
    shapeTypes.add(Circle.class);
    shapeTypes.add(Square.class);
    shapeTypes.add(Line.class);
    List<Shape> shapes = new ArrayList<Shape>();
    // Make some shapes:
    for(int i = 0; i < 10; i++)
      shapes.add(Shape.randomFactory());
    // Set all the static colors to GREEN:
    for(int i = 0; i < 10; i++)
      ((Shape)shapes.get(i)).setColor(Shape.GREEN);
    // Save the state vector:
    ObjectOutputStream out = new ObjectOutputStream(
      new FileOutputStream("CADState.out"));
    out.writeObject(shapeTypes);
    Line.serializeStaticState(out);
    out.writeObject(shapes);
    // Display the shapes:
    System.out.println(shapes);
  }
} /* Output:
[class Circlecolor[3] xPos[58] yPos[55] dim[93]
, class Squarecolor[3] xPos[61] yPos[61] dim[29]
, class Linecolor[3] xPos[68] yPos[0] dim[22]
, class Circlecolor[3] xPos[7] yPos[88] dim[28]
, class Squarecolor[3] xPos[51] yPos[89] dim[9]
, class Linecolor[3] xPos[78] yPos[98] dim[61]
, class Circlecolor[3] xPos[20] yPos[58] dim[16]
, class Squarecolor[3] xPos[40] yPos[11] dim[22]
, class Linecolor[3] xPos[4] yPos[83] dim[6]
, class Circlecolor[3] xPos[75] yPos[10] dim[42]
]
*///:~

3.1_2）反序列化

（这里的静态变量颜色属性序列化没有实现Circlecolor[1]Squarecolor[0]Linecolor[3] 注意为什么是1 0 3 着三个数字）

public class RecoverCADState {
  @SuppressWarnings("unchecked")
  public static void main(String[] args) throws Exception {
    ObjectInputStream in = new ObjectInputStream(
      new FileInputStream("CADState.out"));
    // Read in the same order they were written:
    List<Class<? extends Shape>> shapeTypes =
      (List<Class<? extends Shape>>)in.readObject();
    Line.deserializeStaticState(in);
    List<Shape> shapes = (List<Shape>)in.readObject();
    System.out.println(shapes);
  }
} /* Output:
[class Circlecolor[1] xPos[58] yPos[55] dim[93]
, class Squarecolor[0] xPos[61] yPos[61] dim[29]
, class Linecolor[3] xPos[68] yPos[0] dim[22]
, class Circlecolor[1] xPos[7] yPos[88] dim[28]
, class Squarecolor[0] xPos[51] yPos[89] dim[9]
, class Linecolor[3] xPos[78] yPos[98] dim[61]
, class Circlecolor[1] xPos[20] yPos[58] dim[16]
, class Squarecolor[0] xPos[40] yPos[11] dim[22]
, class Linecolor[3] xPos[4] yPos[83] dim[6]
, class Circlecolor[1] xPos[75] yPos[10] dim[42]
]
*///:~

3.2序列化静态变量(实现静态变量序列化)

3.2_1）序列化

abstract class Shape implements Serializable {
  public static final int RED = 1, BLUE = 2, GREEN = 3;
  private int xPos, yPos, dimension;
  private static Random rand = new Random(47);
  private static int counter = 0;
  public abstract void setColor(int newColor);
  public abstract int getColor();
  public Shape(int xVal, int yVal, int dim) {
    xPos = xVal;
    yPos = yVal;
    dimension = dim;
  }
  public String toString() {
    return getClass() +
      "color[" + getColor() + "] xPos[" + xPos +
      "] yPos[" + yPos + "] dim[" + dimension + "]\n";
  }
  public static Shape randomFactory() {
    int xVal = rand.nextInt(100);
    int yVal = rand.nextInt(100);
    int dim = rand.nextInt(100);
    switch(counter++ % 3) {
      default:
      case 0: return new Circle(xVal, yVal, dim);
      case 1: return new Square(xVal, yVal, dim);
      case 2: return new Line(xVal, yVal, dim);
    }
  }
}
 
class Circle extends Shape {
  private static int color = RED;
  public static void
  serializeStaticState(ObjectOutputStream os)
  throws IOException { os.writeInt(color); }
  public static void
  deserializeStaticState(ObjectInputStream os)
  throws IOException { color = os.readInt(); }
  public Circle(int xVal, int yVal, int dim) {
    super(xVal, yVal, dim);
  }
  public void setColor(int newColor) { color = newColor; }
  public int getColor() { return color; }
}
 
class Square extends Shape {
  private static int color;
  public static void
  serializeStaticState(ObjectOutputStream os)
  throws IOException { os.writeInt(color); }
  public static void
  deserializeStaticState(ObjectInputStream os)
  throws IOException { color = os.readInt(); }
  public Square(int xVal, int yVal, int dim) {
    super(xVal, yVal, dim);
    color = RED;
  }
  public void setColor(int newColor) { color = newColor; }
  public int getColor() { return color; }
}
 
class Line extends Shape {
  private static int color = RED;
  public static void
  serializeStaticState(ObjectOutputStream os)
  throws IOException { os.writeInt(color); }
  public static void
  deserializeStaticState(ObjectInputStream os)
  throws IOException { color = os.readInt(); }
  public Line(int xVal, int yVal, int dim) {
    super(xVal, yVal, dim);
  }
  public void setColor(int newColor) { color = newColor; }
  public int getColor() { return color; }
}
 
public class StoreCADState {
  public static void main(String[] args) throws Exception {
    List<Class<? extends Shape>> shapeTypes =
      new ArrayList<Class<? extends Shape>>();
    // Add references to the class objects:
    shapeTypes.add(Circle.class);
    shapeTypes.add(Square.class);
    shapeTypes.add(Line.class);
    List<Shape> shapes = new ArrayList<Shape>();
    // Make some shapes:
    for(int i = 0; i < 10; i++)
      shapes.add(Shape.randomFactory());
    // Set all the static colors to GREEN:
    for(int i = 0; i < 10; i++)
      ((Shape)shapes.get(i)).setColor(Shape.GREEN);
    // Save the state vector:
    ObjectOutputStream out = new ObjectOutputStream(
      new FileOutputStream("CADState.out"));
    out.writeObject(shapeTypes);
    Line.serializeStaticState(out);
    Circle.serializeStaticState(out);
    Square.serializeStaticState(out);
    out.writeObject(shapes);
    // Display the shapes:
    System.out.println(shapes);
  }
} /* Output:
[class Circlecolor[3] xPos[58] yPos[55] dim[93]
, class Squarecolor[3] xPos[61] yPos[61] dim[29]
, class Linecolor[3] xPos[68] yPos[0] dim[22]
, class Circlecolor[3] xPos[7] yPos[88] dim[28]
, class Squarecolor[3] xPos[51] yPos[89] dim[9]
, class Linecolor[3] xPos[78] yPos[98] dim[61]
, class Circlecolor[3] xPos[20] yPos[58] dim[16]
, class Squarecolor[3] xPos[40] yPos[11] dim[22]
, class Linecolor[3] xPos[4] yPos[83] dim[6]
, class Circlecolor[3] xPos[75] yPos[10] dim[42]
]
*///:~

3.2_2）反序列化

public class RecoverCADState {
  @SuppressWarnings("unchecked")
  public static void main(String[] args) throws Exception {
    ObjectInputStream in = new ObjectInputStream(
      new FileInputStream("CADState.out"));
    // Read in the same order they were written:
    List<Class<? extends Shape>> shapeTypes =
      (List<Class<? extends Shape>>)in.readObject();
    Line.deserializeStaticState(in);
    Circle.deserializeStaticState(in);
    Square.deserializeStaticState(in);
    List<Shape> shapes = (List<Shape>)in.readObject();
    System.out.println(shapes);
  }
} /* Output:
[class bin.Practice.Circlecolor[3] xPos[58] yPos[55] dim[93]
, class bin.Practice.Squarecolor[3] xPos[61] yPos[61] dim[29]
, class bin.Practice.Linecolor[3] xPos[68] yPos[0] dim[22]
, class bin.Practice.Circlecolor[3] xPos[7] yPos[88] dim[28]
, class bin.Practice.Squarecolor[3] xPos[51] yPos[89] dim[9]
, class bin.Practice.Linecolor[3] xPos[78] yPos[98] dim[61]
, class bin.Practice.Circlecolor[3] xPos[20] yPos[58] dim[16]
, class bin.Practice.Squarecolor[3] xPos[40] yPos[11] dim[22]
, class bin.Practice.Linecolor[3] xPos[4] yPos[83] dim[6]
, class bin.Practice.Circlecolor[3] xPos[75] yPos[10] dim[42]
]
*///:~

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