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:

1. #![allow(unused)]
2. fn main() {
3. //! Rust <-> Java FFI demo.

5. use jni::objects::{JClass, JString};
6. use jni::sys::jstring;
7. use jni::JNIEnv;

9. /// HelloWorld::hello method implementation.
10. #[no_mangle]
11. pub extern "system" fn Java_HelloWorld_hello(
12. env: JNIEnv,
13. _class: JClass,
14. name: JString,
15. ) -> jstring {
16. let input: String = env.get_string(name).unwrap().into();
17. let greeting = format!("Hello, {input}!");
18. let output = env.new_string(greeting).unwrap();
19. output.into_inner()
20. }
21. }

interoperability/java/Android.bp:

1. rust_ffi_shared {
2. name: "libhello_jni",
3. crate_name: "hello_jni",
4. srcs: ["src/lib.rs"],
5. rustlibs: ["libjni"],
6. }

We then call this function from Java:

interoperability/java/HelloWorld.java:

1. class HelloWorld {
2. private static native String hello(String name);

4. static {
5. System.loadLibrary("hello_jni");
6. }

8. public static void main(String[] args) {
9. String output = HelloWorld.hello("Alice");
10. System.out.println(output);
11. }
12. }

interoperability/java/Android.bp:

1. java_binary {
2. name: "helloworld_jni",
3. srcs: ["HelloWorld.java"],
4. main_class: "HelloWorld",
5. required: ["libhello_jni"],
6. }

最后，您可以构建、同步和运行二进制文件：

1. m helloworld_jni
2. adb sync  # requires adb root && adb remount
3. adb shell /system/bin/helloworld_jni