s000_hello.rs

use jni::objects::{JClass, JString};
use jni::sys::jstring;
use jni::JNIEnv;

#[no_mangle]
pub extern "system" fn Java_sample_s000_HelloWorld_hello<'local>(
    mut env: JNIEnv<'local>,
    // This is the class that owns our static method. It's not going to be used,
    // but still must be present to match the expected signature of a static
    // native method.
    _class: JClass<'local>,
    input: JString<'local>,
) -> jstring {
    // First, we have to get the string out of Java. Check out the `strings`
    // module for more info on how this works.
    let input: String = env
        .get_string(&input)
        .expect("Couldn't get java string!")
        .into();

    // Then we have to create a new Java string to return. Again, more info
    // in the `strings` module.
    let output = env
        .new_string(format!("Hello, {}!", input))
        .expect("Couldn't create java string!");

    // Finally, extract the raw pointer to return.
    output.into_raw()
}