Databases
StackOverflow2013
Postsdbo
POjava.io.InvalidClassException in serialization
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POjava.io.InvalidClassException in serialization
    primarykey
    data
    text
    <p>after reading for serialization, i tried to perform an experiment on the example provided in the book. Following code has some variation and this is basically picked from SCJP book.</p> <pre><code>import java.io.FileInputStream; public class SerializationTest { public static void main(String[] args) { Collar c = new Collar(4); Dog d = new Dog(c, "Sheru", 32); FileOutputStream fos = null; ObjectOutputStream oos = null; try { fos = new FileOutputStream( "C:\\Users\\dell\\Desktop\\NewDir\\DogState.txt"); oos = new ObjectOutputStream(fos); oos.writeObject(d); } catch (IOException e) { e.printStackTrace(); } finally { try { oos.close(); fos.close(); } catch (IOException e) { e.printStackTrace(); } } // *************************************************************************************************** // // Dog restore = null; FileInputStream fis = null; ObjectInputStream ois = null; try { fis = new FileInputStream( "C:\\Users\\dell\\Desktop\\NewDir\\DogState.txt"); ois = new ObjectInputStream(fis); restore = (Dog) ois.readObject(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } finally { try { fis.close(); ois.close(); } catch (IOException e) { e.printStackTrace(); } } System.out.println("after: dog name: "+ restore.name +" , collar=" + restore.getCollar()); System.out.println("Animal material is:" + restore.getWeight()); } } // Intentionally added parameterized constructor so that default constructor is not called. class Animal{ int weight = 42; public Animal(int weight) { this.weight = weight; System.out.println("animal constructor"); } } class Dog extends Animal implements Serializable { String name; transient Collar collar; public Collar getCollar() { return collar; } public void setCollar(Collar collar) { this.collar = collar; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } public Dog(Collar collar, String name, int weight) { super(weight); System.out.println("Dog constructor"); this.collar = collar; this.name = name; } } class Collar { int size; public Collar(int size) { System.out.println("Collar constructor"); this.size = size; } } </code></pre> <p>Here my question is why InvalidClassException is occuring, Please explain what is the root cause of exception. Current output is </p> <pre><code>Collar constructor animal constructor Dog constructor java.io.InvalidClassException: Dog; Dog; 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 SerializationTest.main(SerializationTest.java:39) Caused by: java.io.InvalidClassException: Dog; no valid constructor at java.io.ObjectStreamClass.&lt;init&gt;(Unknown Source) at java.io.ObjectStreamClass.lookup(Unknown Source) at java.io.ObjectOutputStream.writeObject0(Unknown Source) at java.io.ObjectOutputStream.writeObject(Unknown Source) at SerializationTest.main(SerializationTest.java:18) Exception in thread "main" java.lang.NullPointerException at SerializationTest.main(SerializationTest.java:54) </code></pre> <p>If i remove Animal constructor and comment out the super(weight) in Dog constructor, then output is </p> <pre><code>Collar constructor Dog constructor after: dog name: Sheru , collar=null Animal material is:42 </code></pre> <p>I understand this output, and i also get the fact that during de-serialization serialzable class's superclass constructor is called but here no default constructor is present, so exception occured. But why this exception occur i want to know.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USKanishka Gupta
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COJava doesn't know how to construct a new instance of your class without a default constructor.
      singulars
      1. POjava.io.InvalidClassException in serialization
      1. USMatt Ball
    2. CO@MattBall but the initial error occur while writing the object, and while writing i am providing the object to the JVM and JVM should store( serialize) it into the file. At this point ( storing of object ) why and where creation of object is needed. I read that while de-serializing an object is returned ( and non serialized superclass constructor is called to initialize the value ). But here problem starts with writeObject() not readObject()
      singulars
      1. POjava.io.InvalidClassException in serialization
      1. USKanishka Gupta
    3. COpossible duplicate of [java.io.InvalidClassException: no valid constructor](http://stackoverflow.com/questions/9747443/java-io-invalidclassexception-no-valid-constructor)
      singulars
      1. POjava.io.InvalidClassException in serialization
      1. USh22
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload