Awesome Java Annotation Processing

Java Annotation Processing (defined by JSR 269) is a standardized API for hooking into the Java compiler, allowing you to validate the code under compilation and generate additional (source or byte) code. This Awesome List aims at providing an overview of helpful resources around that API, including existing useful annotation processors, related presentations and blog posts, implementation best practices etc.

Table of Contents

• Existing Annotation Processors
  • Android
• Useful Tools
• Slide Decks and Recordings
• Blog Posts and Articles
• Related Concepts

Existing Annotation Processors

Existing annotation processors for different purposes

• avaje-inject - Compile-time dependency injection library.

• avaje-jsonb - JSON mapping using generated source code

• avaje-http - Generates adapter code for Javalin and Helidon SE/Nima from JAX-RS style controllers.

• chimera - Compile-time static analysis and generation of commands for Spigot plugins.

• dekorate - Generates manifests for Kubernetes/OpenShift.

• Dagger - Compile-time dependency injection framework for both Java and Android.

• derive4j - Java 8 annotation processor and framework for deriving algebraic data types constructors, pattern-matching, folds, optics and typeclasses.

• domino-jackson - Generates Jackson based JSON mappers where the same mapper can be used on the JVM/android or GWT client Javascript code.

• domino-rest - Generates rest clients from JaxRs compatible interfaces.

• Duzzt - Duzzt - Annotation-based Embedded DSL Generator for Java.

• Google Auto - A collection of source code generators for Java.

• Google Error Prone - A static analysis tool for Java that catches common programming mistakes at compile-time.

• Gson Path - A Java annotation processor library which generates gson type adapters using basic JsonPath style annotations.

• Hibernate Validator annotation processor - Compile-time checking of Bean Validation constraints.

• jMolecules annotation processor - Verifies rules attached to jMolecules concepts.

• JPA Static Metamodel Generator - Creates JPA 2 static metamodel classes.

• Immutables - Java annotation processors to generate simple, safe and consistent value objects.

• JMH Generator - Generates Java Microbenchmark Harness (JMH) benchmarks.

• jbock - Generates command line parsers.

• jstachio - A typesafe Java Mustache templating engine that compiles templates into readable Java code.

• Magic Bean - A very basic library which will generate POJOs.

• MapStruct - Compile-time generator for type-safe bean-to-bean mapping code.

• Micronaut - A modern full-stack framework for building modular, easily testable microservice and serverless applications.

• Pojo Analyzer - A library enables looping over POJOs' fields or access them by their names, and retreive their getters & setters.

• Record Builder - Adds Builders and Withers for Java Records (added in Java 16).

• Sundrio - A collection of apt-based code generating tools, including advanced builder generator, dsl generator, velocity transformer and etc.

• Viper - A generator and a framework for injecting configurations via the java EE’s CDI. Put all your configuration keys in an enum, and make viper inject the configurations in your beans.

• chocotea - Generates postman collection, environment and integration tests from Java code.

• sharedtype - Generates type information from Java source code to Typescript, Rust, Go, and more.

Android

Annotation processors specific to Android development

• Butter Knife - Bind Android views and callbacks to fields and methods.

• Parceler - Android Parcelables made easy through code generation.

Useful Tools

Useful tools and libraries for implementing annotation processors

• Apache Velocity - A Java-based template engine

• APTK - A toolbox that helps you to build annotation processors in a more efficient way.

• Avaje Prisms - A JDK 11 fork of Hickory with some minor enhancements.

• Compile Testing - Testing tools for javac and annotation processors.

• Java Compiler Testing - Library for integration testing annotation processors against javac. Supports testing packages and JPMS modules, uses in-memory file systems, and includes integrations with Junit5 and AssertJ.

• CUTE - Testing tools for javac and annotation processors. Allows unit and black box testing.

• Elementary - A suite of JUnit 5 extensions that provides a real annotation processing environment during testing

• JavaPoet - A Java API for generating .java source files.

• Hickory - An annotation processor for generating "prisms", allowing to access known annotation types without class references; Maven coordinates, fork repo (There is no official source repo existing)

Slide Decks and Recordings

• @Eliminate("Boilerplate")

• Annotation Processing Boilerplate Destruction

• Annotation Processor, trésor caché de la JVM (French)

• Annotation Processing Hands-on Labs, Devoxx France 2015 (French)

• Code Generation with Annotation Processors: State of the Art in Java 9

• Das Annotation Processing API - Use Cases und Best Practices (German)

Blog Posts and Articles

• Annotation Processing 101

• Annotation Processing : Don’t Repeat Yourself, Generate Your Code.

• How to Unit Test Your Annotation Processor using jOOR

• Java Annotation Processing: Das könnte auch ein Computer erledigen (German)

• Java Annotation Processing and Creating a Builder

• The Problem with Annotation Processors

• Writing your own Annotation Processors in Android

• Code Generation using Annotation Processors in the Java language

Related Concepts

APIs and tools going beyond what’s doable with JSR 269

• Spoon - Source Code Analysis and Transformation for Java (allows for AST modifications, too)

• javac Plug-in API (allows for full AST inspection)

• Project Lombok - Generates boilerplate Java code like getters/setters and equals/hashCode methods.