Using External Dependencies

The Jextract plugin can consume native headers and binaries from external dependencies. These might be produced by the C++ plugins from Gradle Native.

Dependency Scopes

Each library configuration in the plugin DSL offers a custom dependencies block where native dependencies can be added to certain dependency scopes.

• header dependencies contain public header and binary files.
• headerOnly dependencies contain header files.
• include dependencies contain headers to be added to the include path and corresponding binary files.
• inclodeOnly dependencies contain header files to be added to the include path.
• runtimeOnly dependencies contain binary files.

Header files are used by Jextract, whereas binary files are added to the library path of Java execution tasks like test or run. Local headers, includes, and binaries added to the library configuration take precedence over those coming from dependencies.

Note

In the example project, the app subproject demonstrates this use-case by using a Gradle Native dependency.

Finding the Header File

The Jextract plugin needs exactly one header file. In case the header dependencies contain multiple header files, a headerFilter property can be configured with a set of glob search patterns to narrow down the set to one file. This enables traversing subdirectories or resolving file name ambiguities. Per convention, this set is configured with a pattern inferred from the library’s name. For a library named foo, the plugin would look for a header file named foo.h by default.

Example Configuration

The following example demonstrates the usage of a Gradle Native subproject as dependency in a library named foo, setting bar.h as its header file.

Kotlin

Configuring a library with external dependencies

// build.gradle.kts
jextract.libraries {
    register("foo") {
        dependencies {
            header(project(":foo-project")) // Headers and binaries
            headerFilter = setOf("bar.h")
        }
    }
}

Groovy

Configuring a library with external dependencies

// build.gradle
jextract.libraries {
    register('foo') {
        dependencies {
            header(project(":foo-project")) // Headers and binaries
            headerFilter = ["bar.h"]
        }
    }
}