ShadowySpirits commented on code in PR #2112:
URL:
https://github.com/apache/incubator-opendal/pull/2112#discussion_r1177546688
##########
bindings/java/src/lib.rs:
##########
@@ -15,20 +15,97 @@
// specific language governing permissions and limitations
// under the License.
+use std::cell::RefCell;
use std::collections::HashMap;
+use std::ffi::c_void;
use std::str::FromStr;
+use std::sync::Arc;
-use jni::objects::JClass;
use jni::objects::JMap;
use jni::objects::JObject;
use jni::objects::JString;
-use jni::sys::jboolean;
-use jni::sys::jlong;
-use jni::JNIEnv;
+use jni::objects::{JClass, JValue};
+use jni::sys::{jboolean, jint};
+use jni::sys::{jlong, JNI_VERSION_1_8};
+use jni::{JNIEnv, JavaVM};
+use once_cell::sync::OnceCell;
+use tokio::runtime::{Builder, Runtime};
+
use opendal::BlockingOperator;
use opendal::Operator;
use opendal::Scheme;
+static mut RUNTIME: OnceCell<Runtime> = OnceCell::new();
+
+thread_local! {
+ static JAVA_VM: RefCell<Option<Arc<JavaVM>>> = RefCell::new(None);
+ static JENV: RefCell<Option<*mut jni::sys::JNIEnv>> = RefCell::new(None);
+}
+
+fn get_system_property(env: &mut JNIEnv, key: &str) -> Result<String,
jni::errors::Error> {
+ let system_class = env.find_class("java/lang/System")?;
+ let key = env.new_string(key)?;
+ let value = env.call_static_method(
+ system_class,
+ "getProperty",
+ "(Ljava/lang/String;)Ljava/lang/String;",
+ &[JValue::Object(key.as_ref())],
+ )?;
+
+ Ok(env
+ .get_string(JString::from(value.l().unwrap()).as_ref())?
+ .into())
+}
+
+/// # Safety
+///
+/// This function could be only called by java vm when load this lib.
+#[no_mangle]
+pub unsafe extern "system" fn JNI_OnLoad(vm: JavaVM, _: *mut c_void) -> jint {
+ let mut env = vm.get_env().unwrap();
+ let thread_count = match get_system_property(&mut env,
"opendal.thread.count") {
+ Ok(count) => count.parse().unwrap_or(num_cpus::get()),
+ Err(_) => num_cpus::get(),
+ };
+
+ let java_vm = Arc::new(vm);
+ let runtime = Builder::new_multi_thread()
+ .worker_threads(thread_count)
+ .on_thread_start(move || {
+ JENV.with(|cell| {
+ let env = java_vm.attach_current_thread_as_daemon().unwrap();
+ *cell.borrow_mut() = Some(env.get_raw());
+ });
+ JAVA_VM.with(|cell| {
+ *cell.borrow_mut() = Some(java_vm.clone());
+ });
+ })
+ .on_thread_stop(move || {
+ JENV.with(|cell| {
+ *cell.borrow_mut() = None;
+ });
+ JAVA_VM.with(|cell| unsafe {
+ if let Some(vm) = cell.borrow_mut().take() {
+ vm.detach_current_thread();
+ }
+ });
+ })
+ .build()
+ .unwrap();
+ RUNTIME.set(runtime).unwrap();
+ JNI_VERSION_1_8
Review Comment:
> JNI_OnLoad must return the JNI version needed by the native library
Reference:
https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/invocation.html#JNJI_OnLoad
It is better to select a minimum version that fulfills our requirements,
similar to MSRV.
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