Skip to content

JNI updates to work with swift-java-jni-core #8

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
marcprux wants to merge 2 commits into
base: main
Choose a base branch
from
Open

JNI updates to work with swift-java-jni-core #8

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5aa6eb2
JNI updates to work with swift-java-jni-core
marcprux May 22, 2026
9bcdfe7
Fix jniContext
marcprux May 22, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
111 changes: 60 additions & 51 deletions Sources/SwiftJNI/SwiftJNI.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -65,44 +65,6 @@ public var isJNIInitialized: Bool {
JNI.jni != nil
}

/// Establish a context in which to perform JNI operations.
///
/// - Warning: You cannot initiate JNI operations from native code outside of a context.
public func jniContext<T>(_ block: () throws -> T) rethrows -> T {
precondition(JNI.jni != nil, "JNI.jni was unset")
precondition(JNI.jni._jvm.pointee != nil, "JNI.jni._jvm.pointee was nil")

let jvm: JNIInvokeInterface = JNI.jni._jvm.pointee!.pointee
var tenv: UnsafeMutableRawPointer?
let threadStatus = jvm.GetEnv(JNI.jni._jvm, &tenv, JavaInt(JNI_VERSION_1_6))

// Ensure that there is a `JNIEnvPointer` for the current thread
// See: https://developer.android.com/training/articles/perf-jni#threads
switch threadStatus {
case JNI_OK:
return try block()
case JNI_EDETACHED:
// we weren't attached to the Java thread; attach, perform the block, and then detach
var tenv: JNIEnvPointer!
if jvm.AttachCurrentThread(JNI.jni._jvm, &tenv, nil) != JNI_OK {
fatalError("SwiftJNI: unable to attach JNI to current thread")
}
defer {
if jvm.DetachCurrentThread(JNI.jni._jvm) != JNI_OK {
fatalError("SwiftJNI: unable to detach JNI from thread")
}
}

// We set the ClassLoader for the current thread to be the application ClassLoader, otherwise classes defined in the app may not be found when loaded from a natively-created thread when loaded via reflection
JClassLoader.setThreadClassLoader()
return try block()
case JNI_EVERSION:
fatalError("SwiftJNI: unsupported JNI version")
default:
fatalError("SwiftJNI: unexpected JNI thread status: \(threadStatus)")
}
}

#if SWIFT_JAVA_JNI_CORE
public typealias JNI = SwiftJavaJNICore.JavaVirtualMachine

Expand All @@ -124,19 +86,26 @@ extension JNI {
public convenience init(jvm: UnsafeMutablePointer<JavaVM?>) {
self.init(adoptingJVM: jvm)
}
}

/// Our reference to the Java Virtual Machine, to be set on init
var _jvm: UnsafeMutablePointer<JavaVM?> {
get {
var jvm: UnsafeMutablePointer<JavaVM?>? = nil
let env = try! environment()
guard env.pointee!.pointee.GetJavaVM(env, &jvm) == JNI_OK, let jvm else {
fatalError("unable to call getJavaVM")
}
return jvm
}
extension JNI {
/// Perform an operation with the current thread's `JNIEnviPointer`.
public func withEnv<T>(_ block: (JNINativeInterface, JNIEnvPointer) throws -> T) rethrows -> T {
let env = try! environment()
return try block(env.pointee!.pointee, env)
}
}

/// Establish a context in which to perform JNI operations.
///
/// - Warning: You cannot initiate JNI operations from native code outside of a context.
public func jniContext<T>(_ block: () throws -> T) rethrows -> T {
// We set the ClassLoader for the current thread to be the application ClassLoader, otherwise classes defined in the app may not be found when loaded from a natively-created thread when loaded via reflection
// TODO: cache and optimize
JClassLoader.setThreadClassLoader()
try block()
}

#else
/// Gateway to JVM and JNI functionality.
public class JNI {
Expand All @@ -157,7 +126,6 @@ public class JNI {
self._jvm = jvm
}
}
#endif

extension JNI {
/// Perform an operation with the current thread's `JNIEnviPointer`.
Expand All @@ -171,7 +139,48 @@ extension JNI {
let env = tenv!.assumingMemoryBound(to: JNIEnv?.self)
return try block(env.pointee!.pointee, env)
}
}

/// Establish a context in which to perform JNI operations.
///
/// - Warning: You cannot initiate JNI operations from native code outside of a context.
public func jniContext<T>(_ block: () throws -> T) rethrows -> T {
precondition(JNI.jni != nil, "JNI.jni was unset")
precondition(JNI.jni._jvm.pointee != nil, "JNI.jni._jvm.pointee was nil")

let jvm: JNIInvokeInterface = JNI.jni._jvm.pointee!.pointee
var tenv: UnsafeMutableRawPointer?
let threadStatus = jvm.GetEnv(JNI.jni._jvm, &tenv, JavaInt(JNI_VERSION_1_6))

// Ensure that there is a `JNIEnvPointer` for the current thread
// See: https://developer.android.com/training/articles/perf-jni#threads
switch threadStatus {
case JNI_OK:
return try block()
case JNI_EDETACHED:
// we weren't attached to the Java thread; attach, perform the block, and then detach
var tenv: JNIEnvPointer!
if jvm.AttachCurrentThread(JNI.jni._jvm, &tenv, nil) != JNI_OK {
fatalError("SwiftJNI: unable to attach JNI to current thread")
}
defer {
if jvm.DetachCurrentThread(JNI.jni._jvm) != JNI_OK {
fatalError("SwiftJNI: unable to detach JNI from thread")
}
}

// We set the ClassLoader for the current thread to be the application ClassLoader, otherwise classes defined in the app may not be found when loaded from a natively-created thread when loaded via reflection
JClassLoader.setThreadClassLoader()
return try block()
case JNI_EVERSION:
fatalError("SwiftJNI: unsupported JNI version")
default:
fatalError("SwiftJNI: unexpected JNI thread status: \(threadStatus)")
}
}
#endif

extension JNI {
/// Same as `withEnv`, but also checks for any java exceptions. If an exception occurred,
/// it will throw a `JavaException` and clear the JNI exception.
public func withEnvThrowing<T>(options: JConvertibleOptions, _ block: (JNINativeInterface, JNIEnvPointer) throws -> T) throws -> T {
Expand Down Expand Up @@ -1395,7 +1404,7 @@ extension String: JObjectProtocol, JConvertible {
fatalError("Could not get characters from String")
}
defer { jni.ReleaseStringUTFChars(env, obj, chars) }
guard let str = String(validatingUTF8: chars) else {
guard let str = String(validatingCString: chars) else {
fatalError("Could not get valid UTF8 characters from String")
}
return str
Expand Down Expand Up @@ -1578,7 +1587,7 @@ extension JNI {
}
}
let JAVA_HOME = getenv("JAVA_HOME")!
let javaHome = URL(fileURLWithPath: String(validatingUTF8: JAVA_HOME)!)
let javaHome = URL(fileURLWithPath: String(validatingCString: JAVA_HOME)!)

let ext: String
#if os(Windows)
Expand Down
Loading