What are ObjectInputStream and ObjectOutputStream in java. I am having a problem in a source file saying
Exception in thread “main” java.io.InvalidClassException: Block; invalid descriptor for field
at java.io.ObjectStreamClass.readNonProxy(ObjectStreamClass.java:710)
at java.io.ObjectInputStream.readClassDescriptor(ObjectInputStream.java:828)
ObjectInputStream and ObjectOutputStream are used for deserialization and serialization in java. In serialization we save the state of an object to a file. And in deserialization we retrieve object from the previously saved state. This is heavily used when you want to transfer object over a network.
You can only serialize or deserialize the object of those class that implement Serializable interface. The reason for your error is probably because you are trying to serialize or deserialize the object that doesn’t implement Serializable interface.
The Java ObjectInputStream class (java.io.ObjectInputStream) enables you to read Java objects from an InputStream instead of just raw bytes. You wrap an InputStream in a ObjectInputStream and then you can read objects from it. Of course the bytes read must represent a valid, serialized Java object. Otherwise reading objects will fail.
Normally we use the ObjectInputStream to read objects written (serialized) by a Java ObjectOutputStream.
ObjectInputStream Example
Here is a Java ObjectInputStream example:
ObjectInputStream objectInputStream =
new ObjectInputStream(new FileInputStream("object.data"));
MyClass object = (MyClass) objectInputStream.readObject(); objectInputStream.close();
Here’s a good example of both ObjectInputStreams and ObjectOutputStreams
import java.io.*; public class ObjectInputStreamExample {
public static class Person implements Serializable {
public String name = null;
public int age = 0;
}
public static void main(String[] args) throws IOException, ClassNotFoundException {
ObjectOutputStream objectOutputStream =
new ObjectOutputStream(new FileOutputStream("data/person.bin"));
Person person = new Person();
person.name = "Jakob Jenkov";
person.age = 40;
objectOutputStream.writeObject(person);
objectOutputStream.close();
ObjectInputStream objectInputStream =
new ObjectInputStream(new FileInputStream("data/person.bin"));
Person personRead = (Person) objectInputStream.readObject();
objectInputStream.close();
System.out.println(personRead.name);
System.out.println(personRead.age);
} }
I am not sure about your error. It might possible that any two class versions are exactly identical.
And I think this source file is networking related. That’s all I can help.
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