Serializarea Obiectelor în Java

Clasa ObjectInputStream

Constructor

public ObjectInputStream( java.io.InputStream in )

throws java.io.IOException, java.io.StreamCorruptedException

Create an ObjectInputStream that reads from the specified InputStream. The stream header containing the magic number and version number are read from the stream and verified. This method will block until the corresponding ObjectOutputStream has written and flushed the header.

Metode

int available( ) throws java.io.IOException

void close( ) throws java.io.IOException

final void defaultReadObject( )

throws java.io.IOException, java.lang.ClassNotFoundException, java.io.NotActiveException

int read( bytest data, int offset, int length )

throws java.io.IOException

int read( ) throws java.io.IOException

boolean readBoolean( ) throws java.io.IOException

byte readByte( ) throws java.io.IOException

char readChar( ) throws java.io.IOException

double readDouble( ) throws java.io.IOException

float readFloat( ) throws java.io.IOException

void readFully( bytest data ) throws java.io.IOException

void readFully( bytest data, int offset, int size )

throws java.io.IOException

int readInt( ) throws java.io.IOException

java.lang.String readLine( ) throws java.io.IOException

long readLong( ) throws java.io.IOException

final java.lang.Object readObject( )

throws java.io.OptionalDataException, java.lang.ClassNotFoundException, java.io.IOException

short readShort( ) throws java.io.IOException

int readUnsignedByte( ) throws java.io.IOException

int readUnsignedShort( ) throws java.io.IOException

java.lang.String readUTF( ) throws java.io.IOException

ynchronized void registerValidation( java.io.ObjectInputValidation obj,

int prio )

throws java.io.NotActiveException, java.io.InvalidObjectException

int skipBytes( int len ) throws java.io.IOException

Cuvintul cheie transient

Pentru ca un anumit câmp sa nu fie salvat în urma serializarii, acesta trebuie declarat cu modificatorul transient. Aceste câmpuri vor fi ignorate de metodele writeObject si readObject.

Ex:

private transient x; ® ignorat la serializare

Exemplu:

import java.io.*;

public class TestSerial {

static MyObject obj;

public static void main(String argsst) {

obj = new MyObject(10,20);

try {

FileOutputStream fout = new

FileOutputStream("fisier.tmp");

ObjectOutputStream sout = new

ObjectOutputStream(fout);

sout.writeObject(obj);

sout.flush();

sout.close();

fout.close();

System.out.println("A fost salvat obiectul " + obj);

}

catch (IOException e) {}

System.out.println("Restauram...");

try {

FileInputStream fin = new

FileInputStream("fisier.tmp");

ObjectInputStream sin = new ObjectInputStream(fin);

try {

obj = (MyObject) sin.readObject();

}

catch (ClassNotFoundException e) {}

sin.close();

fin.close();

System.out.println("A fost restaurat obiectul " + obj);

}

catch (IOException e) {}

}

}

class MyObject implements Serializable {

int x;

private transient int y;

public MyObject(int x, int y) {

this.x = x;

this.y = y;

}

public String toString() {

return new String("x=" + x + ", y="+y);

}

}

Rezultatul acestui program va fi :

A fost salvat obiectul x=10, y=20

Restauram...

A fost restaurat obiectul x=10, y=0

Obs. Atunci când o clasa serializabila deriva dintr-o alta clasa, salvarea câmpurilor clasei parinte se va face doar daca si aceasta este serializabila. In caz contrar, subclasa trebuie sa salveze explicit si câmpurile mostenite.