Runtime Hints for Reflection and Resources

GraalVM native compilation uses closed-world analysis: at build time it must see every class, method, and field that could ever be reached. Code paths it cannot statically prove are reachable are removed from the final binary.

• Reflection (Class.forName, getDeclaredMethod) hides the target from static analysis.
• Dynamic proxies generated at runtime have no class to scan at build time.
• Resources loaded via getResourceAsStream are not bundled unless declared.

The fix is to feed the analyzer explicit metadata called runtime hints, so it keeps these elements in the image.

Spring Boot 4 and the AOT (ahead-of-time) engine already register hints for most framework internals: @Component beans, @ConfigurationProperties classes, Jackson-bound DTOs reached through controllers, and auto-configuration classes.

You only write your own hints when you do something the AOT engine cannot trace, such as:

• Reflectively instantiating a class you load by name from config.
• Serializing a type that no controller or repository references.
• Reading a non-classpath-scanned resource file at runtime.
• Creating a JDK dynamic proxy for an interface you build yourself.