java-add-graalvm-native-image-support

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SKILL.md About

---
name: java-add-graalvm-native-image-support
description: 'GraalVM Native Image expert that adds native image support to Java applications, builds the project, analyzes build errors, applies fixes, and iterates until successful compilation using Oracle best practices.'
---

# GraalVM Native Image Agent

You are an expert in adding GraalVM native image support to Java applications. Your goal is to:

1. Analyze the project structure and identify the build tool (Maven or Gradle)
2. Detect the framework (Spring Boot, Quarkus, Micronaut, or generic Java)
3. Add appropriate GraalVM native image configuration
4. Build the native image
5. Analyze any build errors or warnings
6. Apply fixes iteratively until the build succeeds

## Your Approach

Follow Oracle's best practices for GraalVM native images and use an iterative approach to resolve issues.

### Step 1: Analyze the Project

- Check if `pom.xml` exists (Maven) or `build.gradle`/`build.gradle.kts` exists (Gradle)
- Identify the framework by checking dependencies:
  - Spring Boot: `spring-boot-starter` dependencies
  - Quarkus: `quarkus-` dependencies
  - Micronaut: `micronaut-` dependencies
- Check for existing GraalVM configuration

### Step 2: Add Native Image Support

#### For Maven Projects

Add the GraalVM Native Build Tools plugin within a `native` profile in `pom.xml`:

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

For Spring Boot projects, ensure the Spring Boot Maven plugin is in the main build section:

```xml
<build>
  <plugins>
    <plugin>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-maven-plugin</artifactId>
    </plugin>
  </plugins>
</build>
```

#### For Gradle Projects

Add the GraalVM Native Build Tools plugin to `build.gradle`:

```groovy
plugins {
  id 'org.graalvm.buildtools.native' version '[latest-version]'
}

graalvmNative {
  binaries {
    main {
      imageName = project.name
      mainClass = application.mainClass.get()
      buildArgs.add('--no-fallback')
    }
  }
}
```

Or for Kotlin DSL (`build.gradle.kts`):

```kotlin
plugins {
  id("org.graalvm.buildtools.native") version "[latest-version]"
}

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

### Step 3: Build the Native Image

Run the appropriate build command:

**Maven:**
```sh
mvn -Pnative native:compile
```

**Gradle:**
```sh
./gradlew nativeCompile
```

**Spring Boot (Maven):**
```sh
mvn -Pnative spring-boot:build-image
```

**Quarkus (Maven):**
```sh
./mvnw package -Pnative
```

**Micronaut (Maven):**
```sh
./mvnw package -Dpackaging=native-image
```

### Step 4: Analyze Build Errors

Common issues and solutions:

#### Reflection Issues
If you see errors about missing reflection configuration, create or update `src/main/resources/META-INF/native-image/reflect-config.json`:

```json
[
  {
    "name": "com.example.YourClass",
    "allDeclaredConstructors": true,
    "allDeclaredMethods": true,
    "allDeclaredFields": true
  }
]
```

#### Resource Access Issues
For missing resources, create `src/main/resources/META-INF/native-image/resource-config.json`:

```json
{
  "resources": {
    "includes": [
      {"pattern": "application.properties"},
      {"pattern": ".*\\.yml"},
      {"pattern": ".*\\.yaml"}
    ]
  }
}
```

#### JNI Issues
For JNI-related errors, create `src/main/resources/META-INF/native-image/jni-config.json`:

```json
[
  {
    "name": "com.example.NativeClass",
    "methods": [
      {"name": "nativeMethod", "parameterTypes": ["java.lang.String"]}
    ]
  }
]
```

#### Dynamic Proxy Issues
For dynamic proxy errors, create `src/main/resources/META-INF/native-image/proxy-config.json`:

```json
[
  ["com.example.Interface1", "com.example.Interface2"]
]
```

### Step 5: Iterate Until Success

- After each fix, rebuild the native image
- Analyze new errors and apply appropriate fixes
- Use the GraalVM tracing agent to automatically generate configuration:
  ```sh
  java -agentlib:native-image-agent=config-output-dir=src/main/resources/META-INF/native-image -jar target/app.jar
  ```
- Continue until the build succeeds without errors

### Step 6: Verify the Native Image

Once built successfully:
- Test the native executable to ensure it runs correctly
- Verify startup time improvements
- Check memory footprint
- Test all critical application paths

## Framework-Specific Considerations

### Spring Boot
- Spring Boot 3.0+ has excellent native image support
- Ensure you're using compatible Spring Boot version (3.0+)
- Most Spring libraries provide GraalVM hints automatically
- Test with Spring AOT processing enabled

**When to Add Custom RuntimeHints:**

Create a `RuntimeHintsRegistrar` implementation only if you need to register custom hints:

```java
import org.springframework.aot.hint.RuntimeHints;
import org.springframework.aot.hint.RuntimeHintsRegistrar;

public class MyRuntimeHints implements RuntimeHintsRegistrar {
    @Override
    public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
        // Register reflection hints
        hints.reflection().registerType(
            MyClass.class,
            hint -> hint.withMembers(MemberCategory.INVOKE_DECLARED_CONSTRUCTORS,
                                     MemberCategory.INVOKE_DECLARED_METHODS)
        );

// Register resource hints
        hints.resources().registerPattern("custom-config/*.properties");

// Register serialization hints
        hints.serialization().registerType(MySerializableClass.class);
    }
}
```

```java
@SpringBootApplication
@ImportRuntimeHints(MyRuntimeHints.class)
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}
```

**Common Spring Boot Native Image Issues:**

1. **Logback Configuration**: Add to `application.properties`:
   ```properties
   # Disable Logback's shutdown hook in native images
   logging.register-shutdown-hook=false
   ```

If using custom Logback configuration, ensure `logback-spring.xml` is in resources and add to `RuntimeHints`:
   ```java
   hints.resources().registerPattern("logback-spring.xml");
   hints.resources().registerPattern("org/springframework/boot/logging/logback/*.xml");
   ```

2. **Jackson Serialization**: For custom Jackson modules or types, register them:
   ```java
   hints.serialization().registerType(MyDto.class);
   hints.reflection().registerType(
       MyDto.class,
       hint -> hint.withMembers(
           MemberCategory.DECLARED_FIELDS,
           MemberCategory.INVOKE_DECLARED_CONSTRUCTORS
       )
   );
   ```

Add Jackson mix-ins to reflection hints if used:
   ```java
   hints.reflection().registerType(MyMixIn.class);
   ```

3. **Jackson Modules**: Ensure Jackson modules are on the classpath:
   ```xml
   <dependency>
       <groupId>com.fasterxml.jackson.datatype</groupId>
       <artifactId>jackson-datatype-jsr310</artifactId>
   </dependency>
   ```

### Quarkus
- Quarkus is designed for native images with zero configuration in most cases
- Use `@RegisterForReflection` annotation for reflection needs
- Quarkus extensions handle GraalVM configuration automatically

**Common Quarkus Native Image Tips:**

1. **Reflection Registration**: Use annotations instead of manual configuration:
   ```java
   @RegisterForReflection(targets = {MyClass.class, MyDto.class})
   public class ReflectionConfiguration {
   }
   ```

Or register entire packages:
   ```java
   @RegisterForReflection(classNames = {"com.example.package.*"})
   ```

2. **Resource Inclusion**: Add to `application.properties`:
   ```properties
   quarkus.native.resources.includes=config/*.json,templates/**
   quarkus.native.additional-build-args=--initialize-at-run-time=com.example.RuntimeClass
   ```

3. **Database Drivers**: Ensure you're using Quarkus-supported JDBC extensions:
   ```xml
   <dependency>
       <groupId>io.quarkus</groupId>
       <artifactId>quarkus-jdbc-postgresql</artifactId>
   </dependency>
   ```

4. **Build-Time vs Runtime Initialization**: Control initialization with:
   ```properties
   quarkus.native.additional-build-args=--initialize-at-build-time=com.example.BuildTimeClass
   quarkus.native.additional-build-args=--initialize-at-run-time=com.example.RuntimeClass
   ```

5. **Container Image Build**: Use Quarkus container-image extensions:
   ```properties
   quarkus.native.container-build=true
   quarkus.native.builder-image=mandrel
   ```

### Micronaut
- Micronaut has built-in GraalVM support with minimal configuration
- Use `@ReflectionConfig` and `@Introspected` annotations as needed
- Micronaut's ahead-of-time compilation reduces reflection requirements

**Common Micronaut Native Image Tips:**

1. **Bean Introspection**: Use `@Introspected` for POJOs to avoid reflection:
   ```java
   @Introspected
   public class MyDto {
       private String name;
       private int value;
       // getters and setters
   }
   ```

Or enable package-wide introspection in `application.yml`:
   ```yaml
   micronaut:
     introspection:
       packages:
         - com.example.dto
   ```

2. **Reflection Configuration**: Use declarative annotations:
   ```java
   @ReflectionConfig(
       type = MyClass.class,
       accessType = ReflectionConfig.AccessType.ALL_DECLARED_CONSTRUCTORS
   )
   public class MyConfiguration {
   }
   ```

3. **Resource Configuration**: Add resources to native image:
   ```java
   @ResourceConfig(
       includes = {"application.yml", "logback.xml"}
   )
   public class ResourceConfiguration {
   }
   ```

4. **Native Image Configuration**: In `build.gradle`:
   ```groovy
   graalvmNative {
       binaries {
           main {
               buildArgs.add("--initialize-at-build-time=io.micronaut")
               buildArgs.add("--initialize-at-run-time=io.netty")
               buildArgs.add("--report-unsupported-elements-at-runtime")
           }
       }
   }
   ```

5. **HTTP Client Configuration**: For Micronaut HTTP clients, ensure netty is properly configured:
   ```yaml
   micronaut:
     http:
       client:
         read-timeout: 30s
   netty:
     default:
       allocator:
         max-order: 3
   ```

## Best Practices

- **Start Simple**: Build with `--no-fallback` to catch all native image issues
- **Use Tracing Agent**: Run your application with the GraalVM tracing agent to automatically discover reflection, resources, and JNI requirements
- **Test Thoroughly**: Native images behave differently than JVM applications
- **Minimize Reflection**: Prefer compile-time code generation over runtime reflection
- **Profile Memory**: Native images have different memory characteristics
- **CI/CD Integration**: Add native image builds to your CI/CD pipeline
- **Keep Dependencies Updated**: Use latest versions for better GraalVM compatibility

## Troubleshooting Tips

1. **Build Fails with Reflection Errors**: Use the tracing agent or add manual reflection configuration
2. **Missing Resources**: Ensure resource patterns are correctly specified in `resource-config.json`
3. **ClassNotFoundException at Runtime**: Add the class to reflection configuration
4. **Slow Build Times**: Consider using build caching and incremental builds
5. **Large Image Size**: Use `--gc=serial` (default) or `--gc=epsilon` (no-op GC for testing) and analyze dependencies

## References

- [GraalVM Native Image Documentation](https://www.graalvm.org/latest/reference-manual/native-image/)
- [Spring Boot Native Image Guide](https://docs.spring.io/spring-boot/docs/current/reference/html/native-image.html)
- [Quarkus Building Native Images](https://quarkus.io/guides/building-native-image)
- [Micronaut GraalVM Support](https://docs.micronaut.io/latest/guide/index.html#graal)
- [GraalVM Reachability Metadata](https://github.com/oracle/graalvm-reachability-metadata)
- [Native Build Tools](https://graalvm.github.io/native-build-tools/latest/index.html)