Java - ObjectStreamClass Class

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Introduction

The Java ObjectStreamClass class is Serialization's descriptor for classes. It contains the name and serialVersionUID of the class. The ObjectStreamClass for a specific class loaded in this Java VM can be found/created using the lookup method.

Class declaration

Following is the declaration for Java.io.ObjectStreamClass class −

public class ObjectStreamClass
   extends Object
      implements Serializable

Field

Following are the fields for Java.io.ObjectStreamClass class −

• static ObjectStreamField[] NO_FIELDS − This is the serialPersistentFields value indicating no serializable fields.

Class methods

Methods inherited

This class inherits methods from the following classes −

• Java.io.Object

Example - Get the Class of a simple serializable object

The following example shows the usage of ObjectStreamClass forClass() method. We're using ObjectStreamClass.forClass() to inspect the class of a serialized object.

ObjectStreamClassDemo.java

package com.tutorialspoint;

import java.io.ObjectStreamClass;
import java.io.Serializable;

public class ObjectStreamClassDemo {
   public static void main(String[] args) {
      ObjectStreamClass desc = ObjectStreamClass.lookup(Employee.class);
      if (desc != null) {
         System.out.println("Class from ObjectStreamClass: " + desc.forClass().getName());
      } else {
         System.out.println("Class not serializable.");
      }
   }

   static class Employee implements Serializable {
      private static final long serialVersionUID = 1L;
      String name;
      int id;
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Class from ObjectStreamClass: com.tutorialspoint.ObjectStreamClassDemo$Employee

Explanation

• ObjectStreamClass.lookup(Employee.class) returns metadata for the Employee class.

• forClass() gives back the original Class object.

• Helpful when reflecting over serialized types.

Example - Inspect a field in a simple serializable class

The following example shows the usage of ObjectStreamClass getField(String name) method. We're getting metadata for a field named "username" in a User class.

ObjectStreamClassDemo.java

package com.tutorialspoint;

import java.io.ObjectStreamClass;
import java.io.ObjectStreamField;
import java.io.Serializable;

public class ObjectStreamClassDemo {
   public static void main(String[] args) {
      ObjectStreamClass osc = ObjectStreamClass.lookup(User.class);
      ObjectStreamField field = osc.getField("username");

      if (field != null) {
         System.out.println("Field name: " + field.getName());
         System.out.println("Field type: " + field.getType().getSimpleName());
      } else {
         System.out.println("Field 'username' not found.");
      }
   }

   static class User implements Serializable {
      private static final long serialVersionUID = 1L;
      String username;
      int age;
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Field name: username
Field type: String

Explanation

• ObjectStreamClass.lookup(User.class) gets the serialization metadata for User.

• getField("username") returns the ObjectStreamField representing that field.

• You can then access its name, type, and other properties.

Example - Print names of multiple serializable classes dynamically

The following example shows the usage of ObjectStreamClass getName() method. We're iterating through a list of classes and printing their names using ObjectStreamClass.getName().

ObjectStreamClassDemo.java

package com.tutorialspoint;

import java.io.ObjectStreamClass;
import java.io.Serializable;
import java.util.List;

public class ObjectStreamClassDemo {
   public static void main(String[] args) {
      List<Class<?>> classes = List.of(Order.class, String.class, Integer.class);

      for (Class<?> clazz : classes) {
         ObjectStreamClass osc = ObjectStreamClass.lookup(clazz);
         if (osc != null) {
            System.out.println("Serializable: " + osc.getName());
         } else {
            System.out.println("Not serializable: " + clazz.getName());
         }
      }
   }

   static class Order implements Serializable {
      private static final long serialVersionUID = 1L;
      String item;
      int quantity;
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Serializable: com.tutorialspoint.ObjectStreamClassDemo$Order
Serializable: java.lang.String
Serializable: java.lang.Integer

Explanation

• getName() gives you the class names, whether built-in (String, Integer) or custom (Order).

• This is useful for analyzing types at runtime in generic serialization utilities.