Feature (GraalVM SDK Java API Reference)

```
public interface Feature
```
Features allow clients to intercept the native image generation and run custom initialization code at various stages. All code within feature classes is executed during native image generation, and never at run time.
Features have several advantages over static class initializers (which also run during native image generation):
- The different feature methods are called at different stages during native image generation, which gives clients control over when code is executed.
- Feature methods have an access parameter that allows callbacks into the native image generator.
- Feature methods run when the ImageSingletons is already set up, which allows features to prepare data structures that are then used at run time by querying the ImageSingletons .
Implementation classes must have a no-argument constructor, which is used to instantiate a singleton instance for each feature using reflection. The following features are included during native image generation:
- Features explicitly specified on the command line.
- Features referenced as required by another included feature. Required features are added transitively, and initialization methods of required features are called after invoking the constructor and Feature.isInConfiguration(org.graalvm.nativeimage.hosted.Feature.IsInConfigurationAccess) of the requiring features (unless the feature dependencies are cyclic).
Since:

19.0

Nested Class Summary

Nested Classes
Modifier and Type	Interface and Description
`static interface`	`Feature.AfterAnalysisAccess` Access methods available for `Feature.afterAnalysis(org.graalvm.nativeimage.hosted.Feature.AfterAnalysisAccess)`.
`static interface`	`Feature.AfterCompilationAccess` Access methods available for `Feature.afterCompilation(org.graalvm.nativeimage.hosted.Feature.AfterCompilationAccess)`.
`static interface`	`Feature.AfterHeapLayoutAccess` Access methods available for `Feature.afterHeapLayout(org.graalvm.nativeimage.hosted.Feature.AfterHeapLayoutAccess)`.
`static interface`	`Feature.AfterImageWriteAccess` Access methods available for `Feature.afterImageWrite(org.graalvm.nativeimage.hosted.Feature.AfterImageWriteAccess)`.
`static interface`	`Feature.AfterRegistrationAccess` Access methods available for `Feature.afterRegistration(org.graalvm.nativeimage.hosted.Feature.AfterRegistrationAccess)`.
`static interface`	`Feature.BeforeAnalysisAccess` Access methods available for `Feature.beforeAnalysis(org.graalvm.nativeimage.hosted.Feature.BeforeAnalysisAccess)`.
`static interface`	`Feature.BeforeCompilationAccess` Access methods available for `Feature.beforeCompilation(org.graalvm.nativeimage.hosted.Feature.BeforeCompilationAccess)`.
`static interface`	`Feature.BeforeImageWriteAccess` Access methods available for `Feature.beforeImageWrite(org.graalvm.nativeimage.hosted.Feature.BeforeImageWriteAccess)`.
`static interface`	`Feature.BeforeUniverseBuildingAccess` Access methods available for `Feature.beforeUniverseBuilding(org.graalvm.nativeimage.hosted.Feature.BeforeUniverseBuildingAccess)`.
`static interface`	`Feature.CompilationAccess` Access methods available for `Feature.beforeCompilation(org.graalvm.nativeimage.hosted.Feature.BeforeCompilationAccess)` and `Feature.afterCompilation(org.graalvm.nativeimage.hosted.Feature.AfterCompilationAccess)`.
`static interface`	`Feature.DuringAnalysisAccess` Access methods available for `Feature.duringAnalysis(org.graalvm.nativeimage.hosted.Feature.DuringAnalysisAccess)`.
`static interface`	`Feature.DuringSetupAccess` Access methods available for `Feature.duringSetup(org.graalvm.nativeimage.hosted.Feature.DuringSetupAccess)`.
`static interface`	`Feature.FeatureAccess` Access methods that are available for all feature methods.
`static interface`	`Feature.IsInConfigurationAccess` Access methods available for `Feature.isInConfiguration(org.graalvm.nativeimage.hosted.Feature.IsInConfigurationAccess)`.
`static interface`	`Feature.OnAnalysisExitAccess` Access methods available for `Feature.onAnalysisExit(org.graalvm.nativeimage.hosted.Feature.OnAnalysisExitAccess)`.
`static interface`	`Feature.QueryReachabilityAccess` Access reachability methods available for `Feature.afterAnalysis(org.graalvm.nativeimage.hosted.Feature.AfterAnalysisAccess)` and `Feature.duringAnalysis(org.graalvm.nativeimage.hosted.Feature.DuringAnalysisAccess)`.

Method Summary

All Methods Instance Methods Default Methods
Modifier and Type	Method and Description
`default void`	`afterAnalysis(Feature.AfterAnalysisAccess access)` Handler for initializations after analysis and before universe creation.
`default void`	`afterCompilation(Feature.AfterCompilationAccess access)` Handler for initializations after compilation, i.e., before the native image is written.
`default void`	`afterHeapLayout(Feature.AfterHeapLayoutAccess access)` Handler for initializations after the native image heap and code layout.
`default void`	`afterImageWrite(Feature.AfterImageWriteAccess access)` Handler for altering the image (or shared object) that the linker command produced.
`default void`	`afterRegistration(Feature.AfterRegistrationAccess access)` Handler for initializations after all features have been registered and all options have been parsed; but before any initializations for the static analysis have happened.
`default void`	`beforeAnalysis(Feature.BeforeAnalysisAccess access)` Handler for initializations before the static analysis.
`default void`	`beforeCompilation(Feature.BeforeCompilationAccess access)` Handler for initializations before compilation.
`default void`	`beforeImageWrite(Feature.BeforeImageWriteAccess access)` Handler for altering the linker command after the native image has been built and before it is written.
`default void`	`beforeUniverseBuilding(Feature.BeforeUniverseBuildingAccess access)` Handler for code that needs to run before universe building, but after hosted meta-access has been created.
`default void`	`cleanup()` Handler for cleanup.
`default void`	`duringAnalysis(Feature.DuringAnalysisAccess access)` Handler for performing operations during the static analysis.
`default void`	`duringSetup(Feature.DuringSetupAccess access)` Handler for initializations at startup time.
`default String`	`getDescription()` A short description of the feature (e.g., "Enables Truffle support").
`default List<Class<? extends Feature>>`	`getRequiredFeatures()` Returns the list of features that this feature depends on.
`default String`	`getURL()` A URL to documentation or the sources of the feature.
`default boolean`	`isInConfiguration(Feature.IsInConfigurationAccess access)` This method is called immediately after the constructor, to check whether the feature is part of the configuration or not.
`default void`	`onAnalysisExit(Feature.OnAnalysisExitAccess access)` Handler for code that needs to run after the analysis, even if an error has occurred, e.g., like reporting code.

- Method Detail
  - getURL
```
default String getURL()
```
    A URL to documentation or the sources of the feature. The URL will be used as a link for the feature in the build output (if supported by the user's terminal).
    
    Since:
    
    22.2
  - getDescription
```
default String getDescription()
```
    A short description of the feature (e.g., "Enables Truffle support"). The description is displayed to users as part of the build output.
    
    Since:
    
    22.2
  - isInConfiguration
```
default boolean isInConfiguration(Feature.IsInConfigurationAccess access)
```
    This method is called immediately after the constructor, to check whether the feature is part of the configuration or not. If this method returns false, the feature is not included in the list of features and no other methods are called (in particular, the required features are not processed).
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - getRequiredFeatures
```
default List<Class<? extends Feature>> getRequiredFeatures()
```
    Returns the list of features that this feature depends on. As long as the dependency chain is non-cyclic, all required features are processed before this feature.
    
    Since:
    
    19.0
  - afterRegistration
```
default void afterRegistration(Feature.AfterRegistrationAccess access)
```
    Handler for initializations after all features have been registered and all options have been parsed; but before any initializations for the static analysis have happened.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - duringSetup
```
default void duringSetup(Feature.DuringSetupAccess access)
```
    Handler for initializations at startup time. It allows customization of the static analysis setup.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - beforeAnalysis
```
default void beforeAnalysis(Feature.BeforeAnalysisAccess access)
```
    Handler for initializations before the static analysis.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - duringAnalysis
```
default void duringAnalysis(Feature.DuringAnalysisAccess access)
```
    Handler for performing operations during the static analysis. This handler is called after analysis is complete. So all analysis meta data is available. If the handler performs changes, e.g., makes new types or methods reachable, it needs to call Feature.DuringAnalysisAccess.requireAnalysisIteration(). This triggers a new iteration: analysis is performed again and the handler is called again.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - afterAnalysis
```
default void afterAnalysis(Feature.AfterAnalysisAccess access)
```
    Handler for initializations after analysis and before universe creation.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - onAnalysisExit
```
default void onAnalysisExit(Feature.OnAnalysisExitAccess access)
```
    Handler for code that needs to run after the analysis, even if an error has occurred, e.g., like reporting code.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - beforeUniverseBuilding
```
default void beforeUniverseBuilding(Feature.BeforeUniverseBuildingAccess access)
```
    Handler for code that needs to run before universe building, but after hosted meta-access has been created.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    21.1
  - beforeCompilation
```
default void beforeCompilation(Feature.BeforeCompilationAccess access)
```
    Handler for initializations before compilation.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - afterCompilation
```
default void afterCompilation(Feature.AfterCompilationAccess access)
```
    Handler for initializations after compilation, i.e., before the native image is written.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - afterHeapLayout
```
default void afterHeapLayout(Feature.AfterHeapLayoutAccess access)
```
    Handler for initializations after the native image heap and code layout. Objects and methods have their offsets assigned. At this point, no additional objects must be added to the native image heap, i.e., modifying object fields of native image objects that are part of the native image heap is not allowed at this point.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time
    
    Since:
    
    19.0
  - beforeImageWrite
```
default void beforeImageWrite(Feature.BeforeImageWriteAccess access)
```
    Handler for altering the linker command after the native image has been built and before it is written.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time.
    
    Since:
    
    19.0
  - afterImageWrite
```
default void afterImageWrite(Feature.AfterImageWriteAccess access)
```
    Handler for altering the image (or shared object) that the linker command produced.
    
    Parameters:
    
    access - The supported operations that the feature can perform at this time.
    
    Since:
    
    19.0
  - cleanup
```
default void cleanup()
```
    Handler for cleanup. Can be used to cleanup static data. This can avoid memory leaks if native image generation is done many times, e.g. during unit tests.
    Usually, overriding this method can be avoided by putting a configuration object into the ImageSingletons.
    
    Since:
    
    19.0

Interface Feature

Nested Class Summary

Method Summary

Method Detail

getURL

getDescription

isInConfiguration

getRequiredFeatures

afterRegistration

duringSetup

beforeAnalysis

duringAnalysis

afterAnalysis

onAnalysisExit

beforeUniverseBuilding

beforeCompilation

afterCompilation

afterHeapLayout

beforeImageWrite

afterImageWrite

cleanup