Benefits of using serialver over incrementing

Harry,

It is my understanding that serialver is a tool one should only use to provide backward compatibility for a class without an explicit serialVersionUID.

For example, you are working on a Rectangle class that was written over two years ago for a project at work. You notice that while it implements Serializable, it does not have the constant serialVersionUID. You need to implement two new methods but when you try to compile/run you get a java.io.InvalidClassException.

This is because java uses fields and methods to compute the serialVerionUID for you when it is not explicitly provided. Since your new implementation had two new methods, the hash java generates is different and your modified class is incompatible with the last version of Rectangle. Therefore, you use serialver to get the hash that java assigned the previous version.

serialver Rectangle

Rectangle: private static final long serialVersionUID = -5055464683094427547L;

You then copy the constant, paste it into your Rectangle class, and serialize your modified implementation on compile. Now your modified class can maintain backward compatibility and allow you to evolve the Rectangle class by keeping that serialVersionUID.

Of course, there is no need to use serialver for any new class development. Nor would you want to do so. Just assign serialVersionUID to 0L and leave it that way for backward compatibility. This is where your question comes into play. No, there is no benefit to using serialver over assigning 1L, 2L, 3L...nL. However, incrementing is not for backward compatibility, it is for intentional backward incompatibility, and that is a good thing if it is what you need.

Regards,

Chris