Java Compiler Superpowers: Annotation Processors, Error Prone, and Coding Agents

Java has compiler superpowers that most developers never use directly. Did you know you can write code that runs inside javac? That you can inspect classes, methods, types, annotations, and syntax trees while the compiler is working? That you can generate source code, report custom compiler errors, or write checks that understand what code means rather than just what text it contains?

Most Java developers have already used these capabilities indirectly. Frameworks like MapStruct and Spring Boot extend the compiler to generate code and metadata during compilation, making them feel like ordinary framework features when they’re actually compiler extensions.

In this talk we’ll explore another powerful compiler extension: Error Prone, Google’s open-source static analysis framework for Java. Error Prone runs inside javac, understands the structure of your code, catches bug patterns at compile time, and can be extended with custom rules that report diagnostics, suggest fixes, and enforce architectural standards.

We’ll also see why this matters in the age of coding agents. Prompts and documentation can guide an AI, but compiler diagnostics provide deterministic feedback. By turning architecture and coding rules into compiler errors with clear, actionable messages, we can guide both developers and coding agents using the same reliable feedback loop.

You’ll leave with a practical mental model of Java’s compiler extension APIs, understand how Error Prone works, and know how to build your own compile-time checks.

About the venue
Free Times Cafe has bistro-style seating and a full food and drink menu. Please consider helping to support the venue by planning to have supper during the talk.

Speaker Bio
Adib Saikali is a distinguished engineer at Tanzu by Broadcom, focused on helping Tanzu’s largest customers design and build cloud native applications and platforms using Spring and Kubernetes. Adib is the author of Securing Cloud Applications a book that