diff --git a/dist/java/src/mp/code/Workspace.java b/dist/java/src/mp/code/Workspace.java
index dcc94f0d..a122c4a2 100644
--- a/dist/java/src/mp/code/Workspace.java
+++ b/dist/java/src/mp/code/Workspace.java
@@ -1,6 +1,7 @@
 package mp.code;
 
 import java.util.Optional;
+import java.util.UUID;
 
 import mp.code.data.DetachResult;
 import mp.code.exceptions.CodeMPException;
@@ -57,8 +58,8 @@ public void fetchUsers() throws CodeMPException {
 		fetch_buffers(this.ptr);
 	}
 
-	private static native String[] list_buffer_users(long self, String path) throws CodeMPException;
-	public String[] listBufferUsers(String path) throws CodeMPException {
+	private static native UUID[] list_buffer_users(long self, String path) throws CodeMPException;
+	public UUID[] listBufferUsers(String path) throws CodeMPException {
 		return list_buffer_users(this.ptr, path);
 	}
 
@@ -104,8 +105,10 @@ public Optional<String> getUserLeft() {
 			} else return Optional.empty();
 		}
 
-		public boolean hasFileTreeUpdated() {
-			return type == Type.FILE_TREE_UPDATED;
+		public Optional<String> getTargetBuffer() {
+			if(this.type == Type.FILE_TREE_UPDATED) {
+				return Optional.of(this.argument);
+			} else return Optional.empty();
 		}
 
 		private enum Type {
diff --git a/src/ffi/java/buffer.rs b/src/ffi/java/buffer.rs
index 01dec829..41e915df 100644
--- a/src/ffi/java/buffer.rs
+++ b/src/ffi/java/buffer.rs
@@ -1,4 +1,4 @@
-use jni::{objects::{JClass, JObject, JString, JValueGen}, sys::{jlong, jobject, jstring}, JNIEnv};
+use jni::{objects::{JClass, JObject, JValueGen}, sys::{jlong, jobject, jstring}, JNIEnv};
 
 use crate::api::Controller;
 
diff --git a/src/ffi/java/mod.rs b/src/ffi/java/mod.rs
index 982f1161..368c4fa2 100644
--- a/src/ffi/java/mod.rs
+++ b/src/ffi/java/mod.rs
@@ -79,3 +79,25 @@ impl<T> JExceptable<T> for Result<T, uuid::Error> where T: Default {
 		self.unwrap_or_default()
 	}
 }
+
+/// Allows easy conversion for various types into Java objects.
+/// This is essentially the same as [TryInto], but that can't be emplemented on non-local types.
+pub(crate) trait JObjectify<'local> {
+	/// The error type, likely to be [jni::errors::Error].
+	type Error;
+
+	/// Attempts to convert the given object to a [jni::objects::JObject].
+	fn jobjectify(self, env: &mut jni::JNIEnv<'local>) -> Result<jni::objects::JObject<'local>, Self::Error>;
+}
+
+impl<'local> JObjectify<'local> for uuid::Uuid {
+	type Error = jni::errors::Error;
+	fn jobjectify(self, env: &mut jni::JNIEnv<'local>) -> Result<jni::objects::JObject<'local>, jni::errors::Error> {
+		env.find_class("java/util/UUID").and_then(|class| {
+			let (msb, lsb) = self.as_u64_pair();
+			let msb = i64::from_ne_bytes(msb.to_ne_bytes());
+			let lsb = i64::from_ne_bytes(lsb.to_ne_bytes());
+			env.new_object(&class, "(JJ)V", &[jni::objects::JValueGen::Long(msb), jni::objects::JValueGen::Long(lsb)])
+		})
+	}
+}
diff --git a/src/ffi/java/workspace.rs b/src/ffi/java/workspace.rs
index 6dd2cb70..de8cf88d 100644
--- a/src/ffi/java/workspace.rs
+++ b/src/ffi/java/workspace.rs
@@ -1,7 +1,7 @@
 use jni::{objects::{JClass, JObject, JString, JValueGen}, sys::{jlong, jobject, jobjectArray, jstring}, JNIEnv};
 use crate::Workspace;
 
-use super::{JExceptable, RT};
+use super::{JExceptable, JObjectify, RT};
 
 /// Gets the workspace id.
 #[no_mangle]
@@ -166,11 +166,11 @@ pub extern "system" fn Java_mp_code_Workspace_list_1buffer_1users<'local>(
 	let users = RT.block_on(workspace.list_buffer_users(&buffer))
 		.jexcept(&mut env);
 
-	env.find_class("java/lang/String")
-		.and_then(|class| env.new_object_array(users.len() as i32, class, JObject::null()))
+	env.find_class("java/util/UUID")
+		.and_then(|class| env.new_object_array(users.len() as i32, &class, JObject::null()))
 		.map(|arr| {
 			for (idx, user) in users.iter().enumerate() {
-				env.new_string(&user.id)
+				user.id.jobjectify(&mut env)
 					.and_then(|id| env.set_object_array_element(&arr, idx as i32, id))
 					.jexcept(&mut env);
 			}
@@ -204,17 +204,14 @@ pub extern "system" fn Java_mp_code_Workspace_event(
 	RT.block_on(workspace.event())
 		.map(|event| {
 			let (name, arg) = match event {
-				crate::api::Event::FileTreeUpdated => ("FILE_TREE_UPDATED", None),
-				crate::api::Event::UserJoin(arg) => ("USER_JOIN", Some(arg)),
-				crate::api::Event::UserLeave(arg) => ("USER_LEAVE", Some(arg)),
+				crate::api::Event::FileTreeUpdated(arg) => ("FILE_TREE_UPDATED", env.new_string(arg).unwrap_or_default()),
+				crate::api::Event::UserJoin(arg) => ("USER_JOIN", env.new_string(arg).unwrap_or_default()),
+				crate::api::Event::UserLeave(arg) => ("USER_LEAVE", env.new_string(arg).unwrap_or_default()),
 			};
 			let event_type = env.find_class("mp/code/Workspace$Event$Type")
 				.and_then(|class| env.get_static_field(class, name, "Lmp/code/Workspace/Event/Type;"))
 				.and_then(|f| f.l())
 				.jexcept(&mut env);
-			let arg = arg.map(|s| env.new_string(s).jexcept(&mut env))
-				.unwrap_or_default();
-
 			env.find_class("mp/code/Workspace$Event").and_then(|class|
 				env.new_object(
 					class,