TestSerialization.java

import java.io.*;

public class TestSerialization {

   // ***********************************************************************************
   public static void main(String[] args) throws Exception {
      TestSerialization ts = new TestSerialization();
      ts.testInstanceObjest();
      ts.testClassObjest();
   }
      
   // ***********************************************************************************
   void testInstanceObjest() throws Exception{
      
      // Serialize output an Instance Object
      ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("t1.tmp"));
      out.writeObject(new MySerializabe());
      out.flush();
         	   
      // ATTENTION: Changed the static and transient static value after storage
      MySerializabe.si  = 10000;
      MySerializabe.tsi = 100000;
         	   
      // Read back Serialized Instance Object
      ObjectInputStream in = new ObjectInputStream(new FileInputStream("t1.tmp"));
      MySerializabe mys = (MySerializabe)in.readObject();
      in.close();
         	   
      // .............................................................
      // Show the results
      System.out.println("Output from testInstanceObjest():\n");
         	   
      // instant values are serialized
      System.out.println("instance variable str          : " + mys.str);
      System.out.println("instance variable i            : " + mys.i);
         	   
      // static values are not serialized for an instant object!
      // The new value is picked up, not the old ones!
      System.out.println("static variable sstr           : " + mys.sstr);
      System.out.println("static variable si             : " + mys.si);
         	   
      // transient values are not serialized
      System.out.println("transient variable tstr        : " + mys.tstr);
      System.out.println("transient variable ti          : " + mys.ti);
         	   
      // transient static values are not serialized 
      // The new value is picked up, not the old ones!
      System.out.println("transient static variable tsstr: " + mys.tsstr);
      System.out.println("transient static variable tsi  : " + mys.tsi);
   }
      
   // ***********************************************************************************
   void testClassObjest() throws Exception {
      
      // Serialize output Class Object
      Class c = Class.forName("MySerializabe");
      ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("t2.tmp"));
      out.writeObject(c);
      out.flush();
         	   
      // ATTENTION: Changed the static and transient static value after storage
      MySerializabe.si  = 11111;
      MySerializabe.tsi = 111111;
         	   
      // Read back Serialized Class Object
      ObjectInputStream in = new ObjectInputStream(new FileInputStream("t2.tmp"));
      Class cls = (Class)in.readObject();
      in.close();
         	   
      // .............................................................
      // Show the results
      System.out.println("\nOutput from testClassObjest():\n");

      // Only field with static modifier is legal to get value back
      // The new value is picked up, not the old ones!
      // which means they are both not serialized.
      // The conclusion: static and tansient static does not make any differece
      
      System.out.println("static variable sstr           : " + cls.getDeclaredField("sstr").get(cls));
      System.out.println("static variable si             : " + cls.getDeclaredField("si").getInt(cls));
         	   
      System.out.println("transient static variable tsstr: " + cls.getDeclaredField("tsstr").get(cls));
      System.out.println("transient static variable tsi  : " + cls.getDeclaredField("tsi").getInt(cls));
         	   
      // all other fields will cause exceptions
      // uncomment this code and try it out!
      // System.out.println(cls.getDeclaredField("i").get(cls));
         	   	   
         	   
      // .............................................................
      // Obviously the serialzed Class object know all fields in itself
      System.out.println("\n  Print some reflections from Class MySerializabe:");
      System.out.println("     " + cls);
      System.out.println("     " + cls.getDeclaredField("str"));
      System.out.println("     " + cls.getDeclaredField("tstr"));
      System.out.println("     " + cls.getDeclaredField("sstr"));
      System.out.println("     " + cls.getDeclaredField("tsstr"));
      System.out.println("     " + cls.getDeclaredFields());
   }
}

// ***********************************************************************************
class MySerializabe implements Serializable {
                    String str   = "STRING";
             static String sstr  = "STATIC STRING";
   transient        String tstr  = "TRANSIENT STRING";
   transient static String tsstr = "TRANSIENT STATIC STRING";
      
                    int i   = 1;
             static int si  = 10;
   transient        int ti  = 100;
   transient static int tsi = 1000;
}

/* OUTPUT:

Output from testInstanceObjest():

instance variable str          : STRING
instance variable i            : 1
static variable sstr           : STATIC STRING
static variable si             : 10000
transient variable tstr        : null
transient variable ti          : 0
transient static variable tsstr: TRANSIENT STATIC STRING
transient static variable tsi  : 100000

Output from testClassObjest():

static variable sstr           : STATIC STRING
static variable si             : 11111
transient static variable tsstr: TRANSIENT STATIC STRING
transient static variable tsi  : 111111

  Print some reflections from Class MySerializabe:
     class MySerializabe
     java.lang.String MySerializabe.str
     transient java.lang.String MySerializabe.tstr
     static java.lang.String MySerializabe.sstr
     static transient java.lang.String MySerializabe.tsstr
     [Ljava.lang.reflect.Field;@64f64241
*/