- Native Image
- Build Configuration
- Native Image Compatibility and Optimization Guide
- Class Initialization in Native Image
- Static Native Images
- Native Image Options
- Native Image Hosted and Runtime Options
- Native Image C API
- Implementing Native Methods in Java with Native Image
- LLVM Backend for Native Image
- Debug Info Feature
- Points-to Analysis Reports
- Using System Properties in Native Images
- Profile-Guided Optimizations
- Memory Management at Image Run Time
- Generating Heap Dumps from Native Images
- Native Image Maven Plugin
- JCA Security Services on Native Image
- Dynamic Proxy on Native Image
- Java Native Interface (JNI) on Native Image
- Reflection on Native Image
- Accessing Resources in Native Images
- Logging on Native Image
- URL Protocols on Native Image
- Compiler
- GraalVM Updater
- Embedding Reference
- Polyglot Programming
- JVM Languages Reference
- JavaScript and Node.js Reference
- LLVM Languages Reference
- Python Reference
- Ruby Reference
- R Reference Manual
- WebAssembly Reference
Accessing Resources in Native Images
By default, the native image builder will not integrate any of the resources which are on the classpath during the generation into the final image.
To make calls such as Class.getResource()
or Class.getResourceAsStream()
(or the corresponding ClassLoader methods) return specific resources (instead of null), the resources that should be accessible at image run time need to be explicitly specified. This can be done via a configuration file such as the following:
{
"resources": {
"includes": [
{"pattern": "<Java regexp that matches resource(s) to be included in the image>"},
{"pattern": "<another regexp>"},
...
],
"excludes": [
{"pattern": "<Java regexp that matches resource(s) to be excluded from the image>"},
{"pattern": "<another regexp>"},
...
]
}
}
The configuration file’s path must be provided to native-image
with -H:ResourceConfigurationFiles=/path/to/resource-config.json
. Alternatively, individual resource paths can also be specified directly to native-image
:
native-image -H:IncludeResources=<Java regexp that matches resources to be included in the image> -H:ExcludeResources=<Java regexp that matches resources to be excluded from the image> ...
The -H:IncludeResources
and -H:ExcludeResources
options can be passed several times to define more than one regexp to match or exclude resources, respectively.
To see which resources get ultimately included into the image, you can enable the related logging info with -H:Log=registerResource:
.
Example Usage #
Given this project structure:
my-app-root
└── src
├── main
│ └── com.my.app
│ ├── Resource0.txt
│ └── Resource1.txt
└── resources
├── Resource2.txt
└── Resource3.txt
Then:
- All resources can be loaded with
.*/Resource.*txt$
, specified as{"pattern":".*/Resource.*txt$"}
in a configuration file, or-H:IncludeResources='.*/Resource.*txt$'
on the command line. Resource0.txt
can be loaded with.*/Resource0.txt$
.Resource0.txt
andResource1.txt
can be loaded with.*/Resource0.txt$
and.*/Resource1.txt$
(or alternatively with a single.*/(Resource0|Resource1).txt$
).- Also, if we want to include everything except the
Resource2.txt
file, we can simply exclude it with-H:IncludeResources='.*/Resource.*txt$'
followed by-H:ExcludeResources='.*/Resource2.txt$'
.
See also the guide on assisted configuration of Java resources and other dynamic features.
Resource Bundles in Native Image #
Java localization support (java.util.ResourceBundle
) enables Java code to load L10N resources and show the right user messages suitable for actual runtime settings like time locale and format, etc.
Native Image needs ahead-of-time knowledge of the resource bundles your application needs so that it can load and store the appropriate bundles for usage in the generated binary. The bundles can be specified in the resource configuration file (see above), in the bundles
section:
{
"bundles": [
{"name":"your.pkg.Bundle"},
{"name":"another.pkg.Resource"},
{"name":"etc.Bundle"}
],
"resources": <see above>
}
Alternatively, bundles can be specified directly as options to native-image
as follows:
native-image -H:IncludeResourceBundles=your.pgk.Bundle,another.pkg.Resource,etc.Bundle ...