Serialization - Revision history

Suhridk at 08:00, 30 August 2011

2011-08-30T08:00:37Z

Suhridk: /* Intro */

2011-08-30T07:59:44Z

Intro

Suhridk: /* writeObject and readObject */

2011-08-30T07:42:18Z

writeObject and readObject

Suhridk: /* Intro */

2011-08-30T07:40:22Z

Intro

Suhridk: /* Intro */

2011-08-30T07:25:50Z

Intro

Suhridk: /* Intro */

2011-08-30T07:23:33Z

Intro

Suhridk: Created page with "== Intro == * Mechanism to persist state of objects * ObjectOutputStream.writeObject() - serialize and write * ObjectInputStream.readObject() - read and deserialize [[Catego..."

2011-08-30T06:40:34Z

Created page with "== Intro == * Mechanism to persist state of objects * ObjectOutputStream.writeObject() - serialize and write * ObjectInputStream.readObject() - read and deserialize [[Catego..."

New page

== Intro ==

* Mechanism to persist state of objects
* ObjectOutputStream.writeObject() - serialize and write
* ObjectInputStream.readObject() - read and deserialize

[[Category:OCPJP]]

@@ Line 69: / Line 69: @@
 </syntaxhighlight>
 == writeObject and readObject==
@@ Line 274: / Line 193: @@
 </syntaxhighlight>
 [[Category:OCPJP]]

← Older revision		Revision as of 07:59, 30 August 2011
Line 69:		Line 69:

	</syntaxhighlight>		</syntaxhighlight>
		+
		+	== Inheritance and Serialization ==
		+
		+	* During deser, constructor does not run and instance initializers are not run.
		+	* However every non-serializable superclass's constructor will run !
		+	* So a non-serializable superclass constructor can overrwrite an instance variable's value if it runs!
		+
		+	<syntaxhighlight lang="java5">
		+
		+	import java.io.*;
		+
		+	class Gadget {
		+
		+	int val = 10;
		+
		+	protected int getVal() {
		+	return val;
		+	}
		+
		+	protected void setVal(int val) {
		+	this.val = val;
		+	}
		+
		+	Gadget() {
		+	System.out.println("Gadget Constructor");
		+	}
		+	}
		+
		+	class Phone extends Gadget implements Serializable {
		+
		+	Phone() {
		+	System.out.println("Phone Constructor");
		+	}
		+
		+	}
		+
		+	public class Ser2 {
		+
		+	public static void main(String[] args) {
		+
		+	try {
		+
		+	File savFile = new File("phone.sav");
		+	ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(savFile));
		+	Phone op = new Phone();
		+	op.setVal(30);
		+	os.writeObject(op);
		+	System.out.println("Serialized Phone with val :" + op.getVal());
		+	os.close();
		+
		+	ObjectInputStream is = new ObjectInputStream(new FileInputStream(savFile));
		+	Phone p = (Phone) is.readObject();
		+	System.out.println("Deserialized Phone");
		+	System.out.println("Phone Val : " + p.getVal());
		+	is.close();
		+
		+	} catch (Exception e) {
		+	e.printStackTrace();
		+	}
		+
		+	}
		+
		+	}
		+
		+	/*
		+
		+	Output : Note Phone Constructor does not run during deser, but Gadget does thus overrwriting val
		+
		+	Gadget Constructor
		+	Phone Constructor
		+	Serialized Phone with val :30
		+	Gadget Constructor
		+	Deserialized Phone
		+	Phone Val : 10
		+
		+	*/
		+
		+
		+	</syntaxhighlight>
		+
		+	[[Category:OCPJP]]

	== writeObject and readObject==		== writeObject and readObject==

← Older revision		Revision as of 07:42, 30 August 2011
Line 87:		Line 87:

	* For e.g. in the above case since Thing is transient, we can save Thing's name field instead during serialization and rebuild Thing object using the name during deserialization.		* For e.g. in the above case since Thing is transient, we can save Thing's name field instead during serialization and rebuild Thing object using the name during deserialization.
		+	* Before we save/retrieve our custom field, os.defaultWriteObject() and defaultReadObject() must be called to handle the normal serialization process.

	<syntaxhighlight lang="java5">		<syntaxhighlight lang="java5">

@@ Line 62: / Line 62: @@
 			os.close();
 		} catch (IOException e) {
 			e.printStackTrace();
+		}

@@ Line 9: / Line 9: @@
 <syntaxhighlight lang="java5">
 class Thing {
+}
@@ Line 35: / Line 47: @@
 	public static void main(String[] args) {
-		Majig m1 = new Majig(1, new Thing());
+		Majig m1 = new Majig(1, new Thing("T1"));
-		Majig m2 = new Majig(2, new Thing());
+		Majig m2 = new Majig(2, new Thing("T2"));
 		File savFile = new File("majig.sav");
@@ Line 55: / Line 67: @@
+}
 </syntaxhighlight>
 [[Category:OCPJP]]

@@ Line 4: / Line 4: @@
 * ObjectOutputStream.writeObject() - serialize and write
 * ObjectInputStream.readObject() - read and deserialize
 [[Category:OCPJP]]