Posts Tagged ‘SpringBoot3’
[SpringIO2022] Ahead Of Time and Native in Spring Boot 3.0
At Spring I/O 2022 in Barcelona, Brian Clozel and Stéphane Nicoll, both engineers at VMware, delivered a comprehensive session on Ahead Of Time (AOT) processing and native compilation in Spring Boot 3.0 and Spring Framework 6.0. Their talk explored the integration of GraalVM native capabilities, detailing the AOT engine’s design, its use by libraries, and practical steps for developers. Through a live demo, they showcased how to transform a Spring application into a native binary, highlighting performance gains and configuration challenges.
GraalVM Native Compilation: Core Concepts
Brian opened by introducing GraalVM, a versatile JVM supporting multiple languages and optimized Just-In-Time (JIT) compilation. The talk focused on its native compilation feature, which transforms Java applications into standalone binaries for specific CPU architectures. This process involves static analysis at build time, processing all classes on a fixed classpath, and determining reachable code. Benefits include memory efficiency (megabytes instead of gigabytes), millisecond startup times, and suitability for CLI tools, serverless functions, and high-density container deployments.
However, challenges exist. Static analysis may require additional reachability metadata for reflection or resources, as GraalVM cannot always infer runtime behavior. Brian demonstrated a case where reflection-based method invocation fails without metadata, as the native image excludes unreachable code. Debugging is less straightforward than with traditional JVMs, and Java agents, like OpenTelemetry, are unsupported. The speakers emphasized that AOT aims to bridge these gaps, making native compilation accessible for Spring applications.
Spring’s AOT Engine: Design and Integration
Stéphane detailed the AOT engine, a core component of Spring Framework 6.0-M4 and Spring Boot 3.0-M3, designed to preprocess application configurations at build time. Unlike annotation processors, it operates post-compilation, analyzing the bean factory and generating Java code to replace dynamic configuration parsing. This code, viewable in modern IDEs like IntelliJ, mimics hand-written configurations but is automatically generated, preserving package visibility and including Javadoc for clarity.
The engine supports two approaches: contributing reachability metadata for reflection or resources, or generating code to simplify static analysis. For example, a demo CLI application used Spring’s RuntimeHints API to register reflection for a SimpleHelloService class and include a classpath resource. The native build tools Gradle plugin, provided by the GraalVM team, integrates with Spring Boot’s plugin to trigger AOT processing and native compilation. Stéphane showed how the generated binary achieved rapid startup and low memory usage, with configuration classes handled automatically by the AOT engine.
Developer Cookbook: Making Applications Native-Ready
The speakers introduced a developer cookbook to guide Spring users toward native compatibility. The first step is running the application in AOT mode on the JVM, validating the engine’s understanding of the configuration without native compilation. This mode pre-processes the bean factory, reducing startup time and exposing issues early. Next, developers should reuse existing test suites, adapting them for AOT using generated sources and JUnit support. This identifies missing metadata, such as reflection or resource hints.
For third-party libraries or custom code, developers can contribute hints via the RuntimeHints API or validate them using a forthcoming Java agent. The GraalVM team is developing a reachability metadata repository, where the Spring team is contributing hints for popular libraries, reducing manual configuration. For advanced cases, developers can hook into the AOT engine to generate custom code, supported by a test compiler API to verify outcomes. Brian emphasized balancing hints and code generation, favoring simplicity unless performance demands otherwise.
Future Directions and Community Collaboration
The talk concluded with a roadmap for Spring Boot 3.0 and Spring Framework 6.0, targeting general availability by late 2022. The current milestones provide robust AOT infrastructure, with future releases expanding support for Spring libraries. The speakers highlighted collaboration with the GraalVM team to simplify native adoption and plans to align with Project Leyden for JVM optimizations. They encouraged feedback via the Spring I/O app and invited developers to explore the demo repository, which includes Maven and Gradle configurations.
This session equipped developers with tools to leverage AOT and native compilation, unlocking new use cases like serverless and high-density deployments while maintaining Spring’s developer-friendly ethos.