java.io.InvalidClassException: no valid constructor

Question

When I run below program, I am getting exception as

java.io.InvalidClassException: Files.SerializationMain; Files.SerializationMain; no valid constructor     at java.io.ObjectStreamClass.checkDeserialize(Unknown Source)     at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)     at java.io.ObjectInputStream.readObject0(Unknown Source)     at java.io.ObjectInputStream.readObject(Unknown Source)     at Files.SerializationClass.main(SerializationClass.java:71) Caused by: java.io.InvalidClassException: Files.SerializationMain; no valid constructor     at java.io.ObjectStreamClass.<init>(Unknown Source)     at java.io.ObjectStreamClass.lookup(Unknown Source)     at java.io.ObjectOutputStream.writeObject0(Unknown Source)     at java.io.ObjectOutputStream.writeObject(Unknown Source)     at Files.SerializationClass.main(SerializationClass.java:61) 

I read somewhere that when we serialize any child class then its base class constructor gets fired.

class Parent123 {     int age;     String name;      Parent123(int age,String name) {         System.out.println("We are in Parent123 Constructor");         this.age=age;         this.name=name;     }   }  class SerializationMain extends Parent123 implements Serializable {     int data1;     String data2;      SerializationMain(int data1,String data2)     {         super(20,"test");         this.data1=data1;         this.data2=data2;     }      public void setData1(int data1)     {         this.data1=data1;     }     public void setData2(String data2)     {         this.data2=data2;     }     public String getData2()     {         return data2;     }     public int getData1()     {         return data1;     } }  public class SerializationClass {      public static void main(String args[])     {         System.out.println("Before Creating Object");         SerializationMain s1=new SerializationMain(10,"Anurag");         try         {             System.out.println("Serializing Object");             FileOutputStream fis=new FileOutputStream("Test.ser");             ObjectOutputStream ois=new ObjectOutputStream(fis);             ois.writeObject(s1);         } catch(Exception e1) {             e1.printStackTrace();         }         try         {             FileInputStream fis=new FileInputStream("Test.ser");             ObjectInputStream ois=new ObjectInputStream(fis);             Object o1=ois.readObject();             SerializationMain s2=(SerializationMain)o1;         }         catch(Exception e1)         {             e1.printStackTrace();         }     } }//End of SerializationClass 

Answer 1

Add implementation of Serializable to parent class.

Answer 2

Just provide default constructor in both classes (Parent & Child)

During deserialization, the fields of non-serializable classes will be initialized using the public or protected no-arg constructor of the class. A no-arg constructor must be accessible to the subclass that is serializable. The fields of serializable subclasses will be restored from the stream. more