GraalVM Native Image for Java Applications

Expert skill for building high-performance native executables from Java applications using GraalVM Native Image, dramatically reducing startup time and memory consumption.

Overview

GraalVM Native Image compiles Java applications ahead-of-time (AOT) into standalone native executables. These executables start in milliseconds, require significantly less memory than JVM-based deployments, and are ideal for serverless functions, CLI tools, and microservices where fast startup and low resource usage are critical.

This skill provides a structured workflow to migrate JVM applications to native binaries, covering build tool configuration, framework-specific patterns, reflection metadata management, and an iterative approach to resolving native build failures.

When to Use

Use this skill when:

• Converting a JVM-based Java application to a GraalVM native executable
• Optimizing cold start times for serverless or containerized deployments
• Reducing memory footprint (RSS) of Java microservices
• Configuring Maven or Gradle with GraalVM Native Build Tools
• Resolving ClassNotFoundException, NoSuchMethodException, or missing resource errors in native builds
• Generating or editing reflect-config.json, resource-config.json, or other GraalVM metadata files
• Using the GraalVM tracing agent to collect reachability metadata
• Implementing RuntimeHints for Spring Boot native support
• Building native images with Quarkus or Micronaut

Instructions

1. Contextual Project Analysis

Before any configuration, analyze the project to determine the build tool, framework, and dependencies:

Detect the build tool:

# Check for Maven
if [ -f "pom.xml" ]; then
    echo "Build tool: Maven"
    # Check for Maven wrapper
    [ -f "mvnw" ] && echo "Maven wrapper available"
fi

# Check for Gradle
if [ -f "build.gradle" ] || [ -f "build.gradle.kts" ]; then
    echo "Build tool: Gradle"
    [ -f "build.gradle.kts" ] && echo "Kotlin DSL"
    [ -f "gradlew" ] && echo "Gradle wrapper available"
fi

Detect the framework by analyzing dependencies:

• Spring Boot: Look for spring-boot-starter-* in pom.xml or build.gradle
• Quarkus: Look for quarkus-* dependencies
• Micronaut: Look for micronaut-* dependencies
• Plain Java: No framework dependencies detected

Check the Java version:

java -version 2>&1
# GraalVM Native Image requires Java 17+ (recommended: Java 21+)

Identify potential native image challenges:

• Reflection-heavy libraries (Jackson, Hibernate, JAXB)
• Dynamic proxy usage (JDK proxies, CGLIB)
• Resource bundles and classpath resources
• JNI or native library dependencies
• Serialization requirements

2. Build Tool Configuration

Configure the appropriate build tool plugin based on the detected environment.

For Maven projects, add a dedicated native profile to keep the standard build clean. See the Maven Native Profile Reference for full configuration.

Key Maven setup:

<profiles>
  <profile>
    <id>native</id>
    <build>
      <plugins>
        <plugin>
          <groupId>org.graalvm.buildtools</groupId>
          <artifactId>native-maven-plugin</artifactId>
          <version>0.10.6</version>
          <extensions>true</extensions>
          <executions>
            <execution>
              <id>build-native</id>
              <goals>
                <goal>compile-no-fork</goal>
              </goals>
              <phase>package</phase>
            </execution>
          </executions>
          <configuration>
            <imageName>${project.artifactId}</imageName>
            <buildArgs>
              <buildArg>--no-fallback</buildArg>
            </buildArgs>
          </configuration>
        </plugin>
      </plugins>
    </build>
  </profile>
</profiles>

Build with: ./mvnw -Pnative package

For Gradle projects, apply the org.graalvm.buildtools.native plugin. See the Gradle Native Plugin Reference for full configuration.

Key Gradle setup (Kotlin DSL):

plugins {
    id("org.graalvm.buildtools.native") version "0.10.6"
}

graalvmNative {
    binaries {
        named("main") {
            imageName.set(project.name)
            buildArgs.add("--no-fallback")
        }
    }
}

Build with: ./gradlew nativeCompile

3. Framework-Specific Configuration

Each framework has its own AOT strategy. Apply the correct configuration based on the detected framework.

Spring Boot (3.x+): Spring Boot has built-in GraalVM support with AOT processing. See the Spring Boot Native Reference for patterns including RuntimeHints, @RegisterReflectionForBinding, and test support.

Key points:

• Use spring-boot-starter-parent 3.x+ which includes the native profile
• Register reflection hints via RuntimeHintsRegistrar
• Run AOT processing with process-aot goal
• Build with: ./mvnw -Pnative native:compile or ./gradlew nativeCompile

Quarkus and Micronaut: These frameworks are designed native-first and require minimal additional configuration. See the Quarkus & Micronaut Reference.

4. GraalVM Reachability Metadata

Native Image uses a closed-world assumption — all code paths must be known at build time. Dynamic features like reflection, resources, and proxies require explicit metadata configuration.

Metadata files are placed in META-INF/native-image/<group.id>/<artifact.id>/:

File	Purpose
reachability-metadata.json	Unified metadata (reflection, resources, JNI, proxies, bundles, serialization)
reflect-config.json	Legacy: Reflection registration
resource-config.json	Legacy: Resource inclusion patterns
proxy-config.json	Legacy: Dynamic proxy interfaces
serialization-config.json	Legacy: Serialization registration
jni-config.json	Legacy: JNI access registration

See the Reflection & Resource Config Reference for complete format and examples.

5. The Iterative Fix Engine

Native image builds often fail due to missing metadata. Follow this iterative approach:

Step 1 — Execute the native build:

# Maven
./mvnw -Pnative package 2>&1 | tee native-build.log

# Gradle
./gradlew nativeCompile 2>&1 | tee native-build.log

Step 2 — Parse build errors and identify the root cause:

Common error patterns and their fixes:

Error Pattern	Cause	Fix
ClassNotFoundException: com.example.MyClass	Missing reflection metadata	Add to reflect-config.json or use @RegisterReflectionForBinding
NoSuchMethodException	Method not registered for reflection	Add method to reflection config
MissingResourceException	Resource not included in native image	Add to resource-config.json
Proxy class not found	Dynamic proxy not registered	Add interface list to proxy-config.json
UnsupportedFeatureException: Serialization	Missing serialization metadata	Add to serialization-config.json

Step 3 — Apply fixes by updating the appropriate metadata file or using framework annotations.

Step 4 — Rebuild and verify. Repeat until the build succeeds.

Step 5 — If manual fixes are insufficient, use the GraalVM tracing agent to collect reachability metadata automatically. See the Tracing Agent Reference.

6. Validation and Benchmarking

Once the native build succeeds:

Verify the executable runs correctly:

# Run the native executable
./target/<app-name>

# For Spring Boot, verify the application context loads
curl http://localhost:8080/actuator/health

Measure startup time:

# Time the startup
time ./target/<app-name>

# For Spring Boot, check the startup log
./target/<app-name> 2>&1 | grep "Started .* in"

Measure memory footprint (RSS):

# On Linux