Java’s built-in serialization, which dates back to early versions, had notable risks. It allowed the deserialization of arbitrary classes. This meant if an attacker could send a crafted object, they might trigger dangerous code paths when deserialized. This led to vulnerabilities like remote code execution. There was also no built-in validation, so you could end up with corrupted or unexpected state. In modern designs, these risks are avoided by using safer, structured approaches like JSON or protocol buffers.

In the recent Java versions, including Java 25, the old native serialization mechanism—often criticized for security risks and inflexibility—is being gradually replaced by more robust approaches. The most notable improvement is the promotion of record classes and serialization frameworks like the Java Serialization Filter or alternatives such as JSON-based serialization (with libraries like Jackson or built-in APIs).

Records simplify immutable data structures and inherently help with safer serialization practices. So yes, there’s a clear push toward more secure and flexible approaches!

JSON is the king of serialization, largely because it's human-readable and easy to integrate across different platforms. Jackson is indeed one of the most popular libraries in Java ecosystems to handle it. You'll typically see RESTful services sending and receiving JSON payloads, with Jackson mapping them directly to Java objects (and vice versa). It's efficient, and since JSON is a de facto standard in the microservices world, Jackson makes it pretty seamless.

So, while JSON is super convenient, it does come with a few trade-offs. First, it’s text-based, so payloads are bigger compared to something binary. Second, it doesn’t have a native type system—numbers might lose precision, and there’s no distinction between, say, integers and floats. Third, it’s not schema-driven, so you don’t have built-in validation or strict structure, which can lead to inconsistencies if not handled carefully. Finally, parsing JSON can be slower and more memory-intensive than some binary formats. Still, it’s so widely supported that the benefits often outweigh these drawbacks!