feat(java): add table names java api (#1279)

Add lancedb-jni and table names API

---------

Co-authored-by: Lei Xu <eddyxu@gmail.com>

java/core/lancedb-jni/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "lancedb-jni"
+description = "JNI bindings for LanceDB"
+# TODO modify lancedb/Cargo.toml for version and dependencies
+version = "0.4.18"
+edition.workspace = true
+repository.workspace = true
+readme.workspace = true
+license.workspace = true
+keywords.workspace = true
+categories.workspace = true
+publish = false
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+lancedb = { path = "../../../rust/lancedb" }
+lance = { workspace = true }
+arrow = { workspace = true, features = ["ffi"] }
+arrow-schema.workspace = true
+tokio = "1.23"
+jni = "0.21.1"
+snafu.workspace = true
+lazy_static.workspace = true
+serde = { version = "^1" }
+serde_json = { version = "1" }

java/core/lancedb-jni/src/connection.rs

@@ -0,0 +1,130 @@
+use crate::ffi::JNIEnvExt;
+use crate::traits::IntoJava;
+use crate::{Error, RT};
+use jni::objects::{JObject, JString, JValue};
+use jni::JNIEnv;
+pub const NATIVE_CONNECTION: &str = "nativeConnectionHandle";
+use crate::Result;
+use lancedb::connection::{connect, Connection};
+
+#[derive(Clone)]
+pub struct BlockingConnection {
+    pub(crate) inner: Connection,
+}
+
+impl BlockingConnection {
+    pub fn create(dataset_uri: &str) -> Result<Self> {
+        let inner = RT.block_on(connect(dataset_uri).execute())?;
+        Ok(Self { inner })
+    }
+
+    pub fn table_names(
+        &self,
+        start_after: Option<String>,
+        limit: Option<i32>,
+    ) -> Result<Vec<String>> {
+        let mut op = self.inner.table_names();
+        if let Some(start_after) = start_after {
+            op = op.start_after(start_after);
+        }
+        if let Some(limit) = limit {
+            op = op.limit(limit as u32);
+        }
+        Ok(RT.block_on(op.execute())?)
+    }
+}
+
+impl IntoJava for BlockingConnection {
+    fn into_java<'a>(self, env: &mut JNIEnv<'a>) -> JObject<'a> {
+        attach_native_connection(env, self)
+    }
+}
+
+fn attach_native_connection<'local>(
+    env: &mut JNIEnv<'local>,
+    connection: BlockingConnection,
+) -> JObject<'local> {
+    let j_connection = create_java_connection_object(env);
+    // This block sets a native Rust object (Connection) as a field in the Java object (j_Connection).
+    // Caution: This creates a potential for memory leaks. The Rust object (Connection) is not
+    // automatically garbage-collected by Java, and its memory will not be freed unless
+    // explicitly handled.
+    //
+    // To prevent memory leaks, ensure the following:
+    // 1. The Java object (`j_Connection`) should implement the `java.io.Closeable` interface.
+    // 2. Users of this Java object should be instructed to always use it within a try-with-resources
+    //    statement (or manually call the `close()` method) to ensure that `self.close()` is invoked.
+    match unsafe { env.set_rust_field(&j_connection, NATIVE_CONNECTION, connection) } {
+        Ok(_) => j_connection,
+        Err(err) => {
+            env.throw_new(
+                "java/lang/RuntimeException",
+                format!("Failed to set native handle for Connection: {}", err),
+            )
+            .expect("Error throwing exception");
+            JObject::null()
+        }
+    }
+}
+
+fn create_java_connection_object<'a>(env: &mut JNIEnv<'a>) -> JObject<'a> {
+    env.new_object("com/lancedb/lancedb/Connection", "()V", &[])
+        .expect("Failed to create Java Lance Connection instance")
+}
+
+#[no_mangle]
+pub extern "system" fn Java_com_lancedb_lancedb_Connection_releaseNativeConnection(
+    mut env: JNIEnv,
+    j_connection: JObject,
+) {
+    let _: BlockingConnection = unsafe {
+        env.take_rust_field(j_connection, NATIVE_CONNECTION)
+            .expect("Failed to take native Connection handle")
+    };
+}
+
+#[no_mangle]
+pub extern "system" fn Java_com_lancedb_lancedb_Connection_connect<'local>(
+    mut env: JNIEnv<'local>,
+    _obj: JObject,
+    dataset_uri_object: JString,
+) -> JObject<'local> {
+    let dataset_uri: String = ok_or_throw!(env, env.get_string(&dataset_uri_object)).into();
+    let blocking_connection = ok_or_throw!(env, BlockingConnection::create(&dataset_uri));
+    blocking_connection.into_java(&mut env)
+}
+
+#[no_mangle]
+pub extern "system" fn Java_com_lancedb_lancedb_Connection_tableNames<'local>(
+    mut env: JNIEnv<'local>,
+    j_connection: JObject,
+    start_after_obj: JObject, // Optional<String>
+    limit_obj: JObject,       // Optional<Integer>
+) -> JObject<'local> {
+    ok_or_throw!(
+        env,
+        inner_table_names(&mut env, j_connection, start_after_obj, limit_obj)
+    )
+}
+
+fn inner_table_names<'local>(
+    env: &mut JNIEnv<'local>,
+    j_connection: JObject,
+    start_after_obj: JObject, // Optional<String>
+    limit_obj: JObject,       // Optional<Integer>
+) -> Result<JObject<'local>> {
+    let start_after = env.get_string_opt(&start_after_obj)?;
+    let limit = env.get_int_opt(&limit_obj)?;
+    let conn =
+        unsafe { env.get_rust_field::<_, _, BlockingConnection>(j_connection, NATIVE_CONNECTION) }?;
+    let table_names = conn.table_names(start_after, limit)?;
+    drop(conn);
+    let j_names = env.new_object("java/util/ArrayList", "()V", &[])?;
+    for item in table_names {
+        let jstr_item = env.new_string(item)?;
+        let item_jobj = JObject::from(jstr_item);
+        let item_gen = JValue::Object(&item_jobj);
+        env.call_method(&j_names, "add", "(Ljava/lang/Object;)Z", &[item_gen])?;
+    }
+    Ok(j_names)
+}

java/core/lancedb-jni/src/error.rs

@@ -0,0 +1,220 @@
+// Copyright 2024 Lance Developers.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::str::Utf8Error;
+
+use arrow_schema::ArrowError;
+use jni::errors::Error as JniError;
+use serde_json::Error as JsonError;
+use snafu::{Location, Snafu};
+
+/// Java Exception types
+pub enum JavaException {
+    IllegalArgumentException,
+    IOException,
+    RuntimeException,
+}
+
+impl JavaException {
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::IllegalArgumentException => "java/lang/IllegalArgumentException",
+            Self::IOException => "java/io/IOException",
+            Self::RuntimeException => "java/lang/RuntimeException",
+        }
+    }
+}
+/// TODO(lu) change to lancedb-jni
+#[derive(Debug, Snafu)]
+#[snafu(visibility(pub))]
+pub enum Error {
+    #[snafu(display("JNI error: {message}, {location}"))]
+    Jni { message: String, location: Location },
+    #[snafu(display("Invalid argument: {message}, {location}"))]
+    InvalidArgument { message: String, location: Location },
+    #[snafu(display("IO error: {message}, {location}"))]
+    IO { message: String, location: Location },
+    #[snafu(display("Arrow error: {message}, {location}"))]
+    Arrow { message: String, location: Location },
+    #[snafu(display("Index error: {message}, {location}"))]
+    Index { message: String, location: Location },
+    #[snafu(display("JSON error: {message}, {location}"))]
+    JSON { message: String, location: Location },
+    #[snafu(display("Dataset at path {path} was not found, {location}"))]
+    DatasetNotFound { path: String, location: Location },
+    #[snafu(display("Dataset already exists: {uri}, {location}"))]
+    DatasetAlreadyExists { uri: String, location: Location },
+    #[snafu(display("Table '{name}' already exists"))]
+    TableAlreadyExists { name: String },
+    #[snafu(display("Table '{name}' was not found"))]
+    TableNotFound { name: String },
+    #[snafu(display("Invalid table name '{name}': {reason}"))]
+    InvalidTableName { name: String, reason: String },
+    #[snafu(display("Embedding function '{name}' was not found: {reason}, {location}"))]
+    EmbeddingFunctionNotFound {
+        name: String,
+        reason: String,
+        location: Location,
+    },
+    #[snafu(display("Other Lance error: {message}, {location}"))]
+    OtherLance { message: String, location: Location },
+    #[snafu(display("Other LanceDB error: {message}, {location}"))]
+    OtherLanceDB { message: String, location: Location },
+}
+
+impl Error {
+    /// Throw as Java Exception
+    pub fn throw(&self, env: &mut jni::JNIEnv) {
+        match self {
+            Self::InvalidArgument { .. }
+            | Self::DatasetNotFound { .. }
+            | Self::DatasetAlreadyExists { .. }
+            | Self::TableAlreadyExists { .. }
+            | Self::TableNotFound { .. }
+            | Self::InvalidTableName { .. }
+            | Self::EmbeddingFunctionNotFound { .. } => {
+                self.throw_as(env, JavaException::IllegalArgumentException)
+            }
+            Self::IO { .. } | Self::Index { .. } => self.throw_as(env, JavaException::IOException),
+            Self::Arrow { .. }
+            | Self::JSON { .. }
+            | Self::OtherLance { .. }
+            | Self::OtherLanceDB { .. }
+            | Self::Jni { .. } => self.throw_as(env, JavaException::RuntimeException),
+        }
+    }
+
+    /// Throw as an concrete Java Exception
+    pub fn throw_as(&self, env: &mut jni::JNIEnv, exception: JavaException) {
+        let message = &format!(
+            "Error when throwing Java exception: {}:{}",
+            exception.as_str(),
+            self
+        );
+        env.throw_new(exception.as_str(), self.to_string())
+            .expect(message);
+    }
+}
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+trait ToSnafuLocation {
+    fn to_snafu_location(&'static self) -> snafu::Location;
+}
+
+impl ToSnafuLocation for std::panic::Location<'static> {
+    fn to_snafu_location(&'static self) -> snafu::Location {
+        snafu::Location::new(self.file(), self.line(), self.column())
+    }
+}
+
+impl From<JniError> for Error {
+    #[track_caller]
+    fn from(source: JniError) -> Self {
+        Self::Jni {
+            message: source.to_string(),
+            location: std::panic::Location::caller().to_snafu_location(),
+        }
+    }
+}
+
+impl From<Utf8Error> for Error {
+    #[track_caller]
+    fn from(source: Utf8Error) -> Self {
+        Self::InvalidArgument {
+            message: source.to_string(),
+            location: std::panic::Location::caller().to_snafu_location(),
+        }
+    }
+}
+
+impl From<ArrowError> for Error {
+    #[track_caller]
+    fn from(source: ArrowError) -> Self {
+        Self::Arrow {
+            message: source.to_string(),
+            location: std::panic::Location::caller().to_snafu_location(),
+        }
+    }
+}
+
+impl From<JsonError> for Error {
+    #[track_caller]
+    fn from(source: JsonError) -> Self {
+        Self::JSON {
+            message: source.to_string(),
+            location: std::panic::Location::caller().to_snafu_location(),
+        }
+    }
+}
+
+impl From<lance::Error> for Error {
+    #[track_caller]
+    fn from(source: lance::Error) -> Self {
+        match source {
+            lance::Error::DatasetNotFound {
+                path,
+                source: _,
+                location,
+            } => Self::DatasetNotFound { path, location },
+            lance::Error::DatasetAlreadyExists { uri, location } => {
+                Self::DatasetAlreadyExists { uri, location }
+            }
+            lance::Error::IO { message, location } => Self::IO { message, location },
+            lance::Error::Arrow { message, location } => Self::Arrow { message, location },
+            lance::Error::Index { message, location } => Self::Index { message, location },
+            lance::Error::InvalidInput { source, location } => Self::InvalidArgument {
+                message: source.to_string(),
+                location,
+            },
+            _ => Self::OtherLance {
+                message: source.to_string(),
+                location: std::panic::Location::caller().to_snafu_location(),
+            },
+        }
+    }
+}
+
+impl From<lancedb::Error> for Error {
+    #[track_caller]
+    fn from(source: lancedb::Error) -> Self {
+        match source {
+            lancedb::Error::InvalidTableName { name, reason } => {
+                Self::InvalidTableName { name, reason }
+            }
+            lancedb::Error::InvalidInput { message } => Self::InvalidArgument {
+                message,
+                location: std::panic::Location::caller().to_snafu_location(),
+            },
+            lancedb::Error::TableNotFound { name } => Self::TableNotFound { name },
+            lancedb::Error::TableAlreadyExists { name } => Self::TableAlreadyExists { name },
+            lancedb::Error::EmbeddingFunctionNotFound { name, reason } => {
+                Self::EmbeddingFunctionNotFound {
+                    name,
+                    reason,
+                    location: std::panic::Location::caller().to_snafu_location(),
+                }
+            }
+            lancedb::Error::Arrow { source } => Self::Arrow {
+                message: source.to_string(),
+                location: std::panic::Location::caller().to_snafu_location(),
+            },
+            lancedb::Error::Lance { source } => Self::from(source),
+            _ => Self::OtherLanceDB {
+                message: source.to_string(),
+                location: std::panic::Location::caller().to_snafu_location(),
+            },
+        }
+    }
+}

java/core/lancedb-jni/src/ffi.rs

@@ -0,0 +1,199 @@
+// Copyright 2024 Lance Developers.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use core::slice;
+
+use jni::objects::{JByteBuffer, JObjectArray, JString};
+use jni::sys::jobjectArray;
+use jni::{objects::JObject, JNIEnv};
+
+use crate::error::{Error, Result};
+
+/// TODO(lu) import from lance-jni without duplicate
+/// Extend JNIEnv with helper functions.
+pub trait JNIEnvExt {
+    /// Get integers from Java List<Integer> object.
+    fn get_integers(&mut self, obj: &JObject) -> Result<Vec<i32>>;
+
+    /// Get strings from Java List<String> object.
+    fn get_strings(&mut self, obj: &JObject) -> Result<Vec<String>>;
+
+    /// Get strings from Java String[] object.
+    /// Note that get Option<Vec<String>> from Java Optional<String[]> just doesn't work.
+    fn get_strings_array(&mut self, obj: jobjectArray) -> Result<Vec<String>>;
+
+    /// Get Option<String> from Java Optional<String>.
+    fn get_string_opt(&mut self, obj: &JObject) -> Result<Option<String>>;
+
+    /// Get Option<Vec<String>> from Java Optional<List<String>>.
+    fn get_strings_opt(&mut self, obj: &JObject) -> Result<Option<Vec<String>>>;
+
+    /// Get Option<i32> from Java Optional<Integer>.
+    fn get_int_opt(&mut self, obj: &JObject) -> Result<Option<i32>>;
+
+    /// Get Option<Vec<i32>> from Java Optional<List<Integer>>.
+    fn get_ints_opt(&mut self, obj: &JObject) -> Result<Option<Vec<i32>>>;
+
+    /// Get Option<i64> from Java Optional<Long>.
+    fn get_long_opt(&mut self, obj: &JObject) -> Result<Option<i64>>;
+
+    /// Get Option<u64> from Java Optional<Long>.
+    fn get_u64_opt(&mut self, obj: &JObject) -> Result<Option<u64>>;
+
+    /// Get Option<&[u8]> from Java Optional<ByteBuffer>.
+    fn get_bytes_opt(&mut self, obj: &JObject) -> Result<Option<&[u8]>>;
+
+    fn get_optional<T, F>(&mut self, obj: &JObject, f: F) -> Result<Option<T>>
+    where
+        F: FnOnce(&mut JNIEnv, &JObject) -> Result<T>;
+}
+
+impl JNIEnvExt for JNIEnv<'_> {
+    fn get_integers(&mut self, obj: &JObject) -> Result<Vec<i32>> {
+        let list = self.get_list(obj)?;
+        let mut iter = list.iter(self)?;
+        let mut results = Vec::with_capacity(list.size(self)? as usize);
+        while let Some(elem) = iter.next(self)? {
+            let int_obj = self.call_method(elem, "intValue", "()I", &[])?;
+            let int_value = int_obj.i()?;
+            results.push(int_value);
+        }
+        Ok(results)
+    }
+
+    fn get_strings(&mut self, obj: &JObject) -> Result<Vec<String>> {
+        let list = self.get_list(obj)?;
+        let mut iter = list.iter(self)?;
+        let mut results = Vec::with_capacity(list.size(self)? as usize);
+        while let Some(elem) = iter.next(self)? {
+            let jstr = JString::from(elem);
+            let val = self.get_string(&jstr)?;
+            results.push(val.to_str()?.to_string())
+        }
+        Ok(results)
+    }
+
+    fn get_strings_array(&mut self, obj: jobjectArray) -> Result<Vec<String>> {
+        let jobject_array = unsafe { JObjectArray::from_raw(obj) };
+        let array_len = self.get_array_length(&jobject_array)?;
+        let mut res: Vec<String> = Vec::new();
+        for i in 0..array_len {
+            let item: JString = self.get_object_array_element(&jobject_array, i)?.into();
+            res.push(self.get_string(&item)?.into());
+        }
+        Ok(res)
+    }
+
+    fn get_string_opt(&mut self, obj: &JObject) -> Result<Option<String>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_string_obj = java_obj_gen.l()?;
+            let jstr = JString::from(java_string_obj);
+            let val = env.get_string(&jstr)?;
+            Ok(val.to_str()?.to_string())
+        })
+    }
+
+    fn get_strings_opt(&mut self, obj: &JObject) -> Result<Option<Vec<String>>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_list_obj = java_obj_gen.l()?;
+            env.get_strings(&java_list_obj)
+        })
+    }
+
+    fn get_int_opt(&mut self, obj: &JObject) -> Result<Option<i32>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_int_obj = java_obj_gen.l()?;
+            let int_obj = env.call_method(java_int_obj, "intValue", "()I", &[])?;
+            let int_value = int_obj.i()?;
+            Ok(int_value)
+        })
+    }
+
+    fn get_ints_opt(&mut self, obj: &JObject) -> Result<Option<Vec<i32>>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_list_obj = java_obj_gen.l()?;
+            env.get_integers(&java_list_obj)
+        })
+    }
+
+    fn get_long_opt(&mut self, obj: &JObject) -> Result<Option<i64>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_long_obj = java_obj_gen.l()?;
+            let long_obj = env.call_method(java_long_obj, "longValue", "()J", &[])?;
+            let long_value = long_obj.j()?;
+            Ok(long_value)
+        })
+    }
+
+    fn get_u64_opt(&mut self, obj: &JObject) -> Result<Option<u64>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_long_obj = java_obj_gen.l()?;
+            let long_obj = env.call_method(java_long_obj, "longValue", "()J", &[])?;
+            let long_value = long_obj.j()?;
+            Ok(long_value as u64)
+        })
+    }
+
+    fn get_bytes_opt(&mut self, obj: &JObject) -> Result<Option<&[u8]>> {
+        self.get_optional(obj, |env, inner_obj| {
+            let java_obj_gen = env.call_method(inner_obj, "get", "()Ljava/lang/Object;", &[])?;
+            let java_byte_buffer_obj = java_obj_gen.l()?;
+            let j_byte_buffer = JByteBuffer::from(java_byte_buffer_obj);
+            let raw_data = env.get_direct_buffer_address(&j_byte_buffer)?;
+            let capacity = env.get_direct_buffer_capacity(&j_byte_buffer)?;
+            let data = unsafe { slice::from_raw_parts(raw_data, capacity) };
+            Ok(data)
+        })
+    }
+
+    fn get_optional<T, F>(&mut self, obj: &JObject, f: F) -> Result<Option<T>>
+    where
+        F: FnOnce(&mut JNIEnv, &JObject) -> Result<T>,
+    {
+        if obj.is_null() {
+            return Ok(None);
+        }
+        let is_empty = self.call_method(obj, "isEmpty", "()Z", &[])?;
+        if is_empty.z()? {
+            // TODO(lu): put get java object into here cuz can only get java Object
+            Ok(None)
+        } else {
+            f(self, obj).map(Some)
+        }
+    }
+}
+
+#[no_mangle]
+pub extern "system" fn Java_com_lancedb_lance_test_JniTestHelper_parseInts(
+    mut env: JNIEnv,
+    _obj: JObject,
+    list_obj: JObject, // List<Integer>
+) {
+    ok_or_throw_without_return!(env, env.get_integers(&list_obj));
+}
+
+#[no_mangle]
+pub extern "system" fn Java_com_lancedb_lance_test_JniTestHelper_parseIntsOpt(
+    mut env: JNIEnv,
+    _obj: JObject,
+    list_obj: JObject, // Optional<List<Integer>>
+) {
+    ok_or_throw_without_return!(env, env.get_ints_opt(&list_obj));
+}

java/core/lancedb-jni/src/lib.rs

@@ -0,0 +1,68 @@
+// Copyright 2024 Lance Developers.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use lazy_static::lazy_static;
+
+// TODO import from lance-jni without duplicate
+#[macro_export]
+macro_rules! ok_or_throw {
+    ($env:expr, $result:expr) => {
+        match $result {
+            Ok(value) => value,
+            Err(err) => {
+                Error::from(err).throw(&mut $env);
+                return JObject::null();
+            }
+        }
+    };
+}
+
+macro_rules! ok_or_throw_without_return {
+    ($env:expr, $result:expr) => {
+        match $result {
+            Ok(value) => value,
+            Err(err) => {
+                Error::from(err).throw(&mut $env);
+                return;
+            }
+        }
+    };
+}
+
+#[macro_export]
+macro_rules! ok_or_throw_with_return {
+    ($env:expr, $result:expr, $ret:expr) => {
+        match $result {
+            Ok(value) => value,
+            Err(err) => {
+                Error::from(err).throw(&mut $env);
+                return $ret;
+            }
+        }
+    };
+}
+
+mod connection;
+pub mod error;
+mod ffi;
+mod traits;
+
+pub use error::{Error, Result};
+
+lazy_static! {
+    static ref RT: tokio::runtime::Runtime = tokio::runtime::Builder::new_multi_thread()
+        .enable_all()
+        .build()
+        .expect("Failed to create tokio runtime");
+}

java/core/lancedb-jni/src/traits.rs

@@ -0,0 +1,122 @@
+// Copyright 2024 Lance Developers.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use jni::objects::{JMap, JObject, JString, JValue};
+use jni::JNIEnv;
+
+use crate::Result;
+
+pub trait FromJObject<T> {
+    fn extract(&self) -> Result<T>;
+}
+
+/// Convert a Rust type into a Java Object.
+pub trait IntoJava {
+    fn into_java<'a>(self, env: &mut JNIEnv<'a>) -> JObject<'a>;
+}
+
+impl FromJObject<i32> for JObject<'_> {
+    fn extract(&self) -> Result<i32> {
+        Ok(JValue::from(self).i()?)
+    }
+}
+
+impl FromJObject<i64> for JObject<'_> {
+    fn extract(&self) -> Result<i64> {
+        Ok(JValue::from(self).j()?)
+    }
+}
+
+impl FromJObject<f32> for JObject<'_> {
+    fn extract(&self) -> Result<f32> {
+        Ok(JValue::from(self).f()?)
+    }
+}
+
+impl FromJObject<f64> for JObject<'_> {
+    fn extract(&self) -> Result<f64> {
+        Ok(JValue::from(self).d()?)
+    }
+}
+
+pub trait FromJString {
+    fn extract(&self, env: &mut JNIEnv) -> Result<String>;
+}
+
+impl FromJString for JString<'_> {
+    fn extract(&self, env: &mut JNIEnv) -> Result<String> {
+        Ok(env.get_string(self)?.into())
+    }
+}
+
+pub trait JMapExt {
+    #[allow(dead_code)]
+    fn get_string(&self, env: &mut JNIEnv, key: &str) -> Result<Option<String>>;
+
+    #[allow(dead_code)]
+    fn get_i32(&self, env: &mut JNIEnv, key: &str) -> Result<Option<i32>>;
+
+    #[allow(dead_code)]
+    fn get_i64(&self, env: &mut JNIEnv, key: &str) -> Result<Option<i64>>;
+
+    #[allow(dead_code)]
+    fn get_f32(&self, env: &mut JNIEnv, key: &str) -> Result<Option<f32>>;
+
+    #[allow(dead_code)]
+    fn get_f64(&self, env: &mut JNIEnv, key: &str) -> Result<Option<f64>>;
+}
+
+fn get_map_value<T>(env: &mut JNIEnv, map: &JMap, key: &str) -> Result<Option<T>>
+where
+    for<'a> JObject<'a>: FromJObject<T>,
+{
+    let key_obj: JObject = env.new_string(key)?.into();
+    if let Some(value) = map.get(env, &key_obj)? {
+        if value.is_null() {
+            Ok(None)
+        } else {
+            Ok(Some(value.extract()?))
+        }
+    } else {
+        Ok(None)
+    }
+}
+
+impl JMapExt for JMap<'_, '_, '_> {
+    fn get_string(&self, env: &mut JNIEnv, key: &str) -> Result<Option<String>> {
+        let key_obj: JObject = env.new_string(key)?.into();
+        if let Some(value) = self.get(env, &key_obj)? {
+            let value_str: JString = value.into();
+            Ok(Some(value_str.extract(env)?))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn get_i32(&self, env: &mut JNIEnv, key: &str) -> Result<Option<i32>> {
+        get_map_value(env, self, key)
+    }
+
+    fn get_i64(&self, env: &mut JNIEnv, key: &str) -> Result<Option<i64>> {
+        get_map_value(env, self, key)
+    }
+
+    fn get_f32(&self, env: &mut JNIEnv, key: &str) -> Result<Option<f32>> {
+        get_map_value(env, self, key)
+    }
+
+    fn get_f64(&self, env: &mut JNIEnv, key: &str) -> Result<Option<f64>> {
+        get_map_value(env, self, key)
+    }
+}