与 Java 的互操作性

Java可以通过 Java 本地接口 (JNI) 加载共享对象。jni crate 允许您创建一个兼容的库。

首先，我们创建一个可以导出到 Java 的 Rust 函数：

interoperability/java/src/lib.rs:

#![allow(unused)]
fn main() {
//! Rust <-> Java FFI demo.
use jni::objects::{JClass, JString};
use jni::sys::jstring;
use jni::JNIEnv;
/// HelloWorld::hello method implementation.
#[no_mangle]
pub extern "system" fn Java_HelloWorld_hello(
    env: JNIEnv,
    _class: JClass,
    name: JString,
) -> jstring {
    let input: String = env.get_string(name).unwrap().into();
    let greeting = format!("Hello, {input}!");
    let output = env.new_string(greeting).unwrap();
    output.into_inner()
}
}

interoperability/java/Android.bp:

rust_ffi_shared {
    name: "libhello_jni",
    crate_name: "hello_jni",
    srcs: ["src/lib.rs"],
    rustlibs: ["libjni"],
}

We then call this function from Java:

interoperability/java/HelloWorld.java:

class HelloWorld {
    private static native String hello(String name);
    static {
        System.loadLibrary("hello_jni");
    }
    public static void main(String[] args) {
        String output = HelloWorld.hello("Alice");
        System.out.println(output);
    }
}

interoperability/java/Android.bp:

java_binary {
    name: "helloworld_jni",
    srcs: ["HelloWorld.java"],
    main_class: "HelloWorld",
    required: ["libhello_jni"],
}

最后，您可以构建、同步和运行二进制文件：

m helloworld_jni
adb sync  # requires adb root && adb remount
adb shell /system/bin/helloworld_jni