What are common mistakes developers make with Externalizable?

Externalizable is an interface in Java that allows developers to control the serialization process of their objects. However, many developers make common mistakes when using Externalizable, which can lead to issues in their applications. Here are a few of those mistakes:

• Not Implementing the writeExternal & readExternal Methods: Developers often forget to implement these essential methods, which define how the serialization and deserialization should occur.
• Incorrect Order of Fields: The order of fields in the writeExternal and readExternal methods must be consistent. Changing the order can lead to deserialization errors.
• Failing to Handle Optional Fields: When dealing with optional fields, it's common to forget to handle these cases, leading to NullPointerExceptions during deserialization.
• Not Writing Default Values: If a field is not serialized, it's expected that a default value is assigned during deserialization. Developers might overlook this, causing inconsistent states.
• Using Externalizable Instead of Serializable: In cases where full control of the serialization process is not needed, choosing Externalizable over Serializable can unnecessarily complicate the code.

Understanding these common pitfalls will help developers utilize Externalizable more effectively in their Java applications.