The serialver is a tool that comes with JDK. It is used to get serialVersionUID numbers of one or more Java classes. Basically, a serializable class must declare a constant named serialVersionUID (either explicitly by the programmer or implicitly by the compiler) like this:

public class User implements Serializable {

	private static final long serialVersionUID = 1234L;
	
}

The serialVersionUID number is important when dealing with the serialization/de-serialization of objects of a class. The serialver command is helpful in case we want to know that number without having source code of the class. Its syntax is as simple as follows:

serialver [-classpath classpath] [-show] [classname...]

The -classpath option specifies where to look for the classes (in directories or jar files, separated by semicolon marks ;). The -show option displays a simple user interface that allows the user to enter a full class name and then press Enter key or click Show button to display the serialVersionUID number.

Now, let’s see some examples.

• Displaying serialVersionUID of a class in default package: Command:

  serialver ProgressBarDemo

  Output:

  ProgressBarDemo:    static final long serialVersionUID = 8449967402779341329L;

  If the specified class is not serializable, then this message is displayed:

  Class ProgressBarDemo is not Serializable.

• Displaying serialVersionUID of a class in a specific package: The following command displays the serialVersionUID of the class SwingEmailSender under the package net.codejava.mail, assuming that the classes are in the build\classes directory:

  serialver -classpath build\classes net.codejava.mail.SwingEmailSender

  Output:

  net.codejava.mail.SwingEmailSender:    static final long serialVersionUID = -2279575288884790698L;

  
  
  
   

• Displaying serialVersionUID numbers of two classes: Command:

  serialver CustomPanel TestSwingZoom

  Output:

  CustomPanel:    static final long serialVersionUID = 6858515184837974475L;
  TestSwingZoom:    static final long serialVersionUID = 4136458911881435009L;

   

• Displaying serialVersionUID of a class inside a jar file: Command:

  serialver -classpath EmailSender.jar net.codejava.swing.JFilePicker

  Output:

  net.codejava.swing.JFilePicker:    static final long serialVersionUID = -6241197264668893626L;

   

• Displaying serialVersionUID of two classes inside two jar files: Command:

  serialver -classpath SwingAudio.jar;SwingUpload.jar net.codejava.AudioPlayer net.codejava.FileUpload

  Output:

  net.codejava.AudioPlayer:    static final long serialVersionUID = 5499535881565379674L;
  net.codejava.FileUpload:    static final long serialVersionUID = 6409440265121275085L;

   

• Showing the user interface: Command:

  serialver -classpath EmailSender.jar -show

  The Serial Version Inspector window gets displayed, enter the full class name and click the Show button to display the serial version:
  

 

References:

• serialver - The Serial Version Command

 

Java Serialization Tutorials:

• Why Do We Need Serialization in Java?
• Java Serialization Basic Example
• Understanding Java Externalization with Examples

 

Other Java Tools Tutorials:

• javac command examples
• java command examples
• Java jar command examples
• Understanding the triad tools javac, java and jar in JDK
• The Java Shell (jshell) Tutorial
• How to compile, package and run a Java program using command-line tools (javac, jar and java)