1

Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "registitemuserust"
+version = "0.1.0"
+edition = "2021"
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+jni = { version = "0.21.1", features = ["invocation"] }
+

src/lib.rs

@@ -0,0 +1,48 @@
+use jni::JNIEnv;
+use jni::objects::{JClass, JObject, JString, JValue, JValueGen, JValueOwned};
+use jni::sys::jint;
+
+#[allow(non_snake_case)]
+#[no_mangle]
+pub unsafe extern "system" fn Java_com_example_FFI_init(
+    mut env:JNIEnv,
+    _class: JClass
+) -> jint
+{
+    println!("Hello From Rust!");
+    //all class we need here
+    let JClass_Registries = env.find_class("net/minecraft/registry/Registries").expect("registries find err");
+    let JClass_Registry = env.find_class("net/minecraft/registry/Registry").expect("registry key find err");
+    let JClass_Identifier = env.find_class("net/minecraft/util/Identifier").expect("Couldn't find Iden class");
+    let JClass_Item = env.find_class("net/minecraft/item/Item").expect("Couldn't find `Item` class!");
+    let JClass_Item_Settings = env.find_class("net/minecraft/item/Item$Settings").expect("Couldn't find `Item settings` class!");
+
+
+    //Item my_dirt = new Item(new Item.settings());
+    let item_settings_obj = env.new_object(JClass_Item_Settings,"()V",&[]).expect("create item_settings_obj error!");
+    let Item_my_dirt = env.new_object(JClass_Item,"(Lnet/minecraft/item/Item$Settings;)V",&[JValueGen::from(&item_settings_obj)]).expect("create item obj error!");
+
+
+    //Identifier item_id =Identifier.of("modid","my_shi");
+    let modid = env.new_string("modid").expect("Couldn't create string");
+    let modid_obj = JObject::from(modid);
+    let my_dirt = env.new_string("dirt").expect("Couldn't create string");
+    let my_dirt_obj = JObject::from(my_dirt);
+    let a = [JValueGen::from(&modid_obj),JValueGen::from(&my_dirt_obj)];
+    let Iden_item_id =
+        env.call_static_method(JClass_Identifier, "of",
+                               "(Ljava/lang/String;Ljava/lang/String;)Lnet/minecraft/util/Identifier;",
+                               &a).expect("Couldn't call Identifier");
+
+
+    //Item regItem = Registry.register(Registries.ITEM,itemID,my_dirt);
+    let ITEMfield = env.get_static_field(JClass_Registries,"ITEM","Lnet/minecraft/registry/Registries;ITEM:Lnet/minecraft/registry/DefaultedRegistry;").expect("ITEM field find err");
+    let register_interface = env.call_static_method(JClass_Registry,"register","Lnet/minecraft/registry/Registry;register(Lnet/minecraft/registry/Registry;Lnet/minecraft/util/Identifier;Ljava/lang/Object;)Ljava/lang/Object;",
+        &[ITEMfield.borrow(),Iden_item_id.borrow(),JValueGen::from(&Item_my_dirt)]
+    ).unwrap();
+
+
+    println!("Done From Rust!");
+    return 0;
+}
+