This library lets you feed plain Java source as a String, compile it in-memory and immediately load the resulting Class<?> - perfect for hot-swapping logic while the JVM is still running.
<!-- Maven --> <dependency> <groupId>net.openhft</groupId> <artifactId>compiler</artifactId> <version>Look up the most recent version on Maven Central.</version> </dependency>
/* Gradle (Kotlin DSL) */ implementation("net.openhft:compiler:Look up the most recent version on Maven Central.")
import net.openhft.compiler.CompilerUtils; String className = "mypackage.MyDynamicClass"; String src = """ package mypackage; public class MyDynamicClass implements Runnable { public void run() { System.out.println("Hello World"); } } """; Class<?> clazz = CompilerUtils.CACHED_COMPILER.loadFromJava(className, src); ((Runnable) clazz.getDeclaredConstructor().newInstance()).run();
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Requires a full JDK (8, 11, 17 or 21 LTS), not a slim JRE.
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On Java 11 + supply these flags (copy-paste safe):
--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED --add-opens=jdk.compiler/com.sun.tools.javac=ALL-UNNAMED
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Spring-Boot / fat-JAR users
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unpack Chronicle jars:
bootJar { requiresUnpack("*/chronicle-.jar") }
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| Feature | Benefit |
|---|---|
In-memory compile & load |
Hot-swap code without restarting JVM |
CachedCompiler |
Skips recompilation of unchanged source |
Debug Mode |
Writes |
Custom ClassLoader support |
Isolate plugins or enable class unloading |
Nested-class handling |
Build helper hierarchy in a single call |
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Hot-swappable strategy interface for trading engines
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Rule-engine: compile business rules implementing
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Supports validator hook to vet user code
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Replace reflection: generate POJO accessors, 10 x faster
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Off-heap accessors with Chronicle Bytes / Map
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Compile on a background thread at start-up; then swap instances.
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Re-use class names or child classloaders to control Metaspace.
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Use
CompilerUtils.DEBUGGING = trueduring dev; remember to prune artefacts.
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SLF4J categories:
net.openhft.compiler(INFO), compilation errors at ERROR. -
Micrometer timers/counters:
compiler.compiles,compiler.failures.
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Project requirements outline functional, non-functional, and compliance obligations.
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Release notes provide the tagged release history.
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`ToolProvider.getSystemJavaCompiler() == null`
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You are running on a JRE; use a JDK.
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`ClassNotFoundException: com.sun.tools.javac.api.JavacTool`
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tools.jar is required on JDK ⇐ 8. Newer JDKs need the
--add-exportsand--add-opensflags. -
Classes never unload
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Generate with a unique
ClassLoaderper version so classes can unload; each loader uses Metaspace. -
Illegal-reflective-access warning
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Add the
--add-opens&--add-exportsflags shown above.
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GitHub Actions workflow runs
mvn verify, unit & race-condition tests.-
Code-coverage report published to SonarCloud badge above.
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