[JExtract] Generate JNI code for classes (static methods and initializers)

Samples/JExtractJNISampleApp/Sources/MySwiftLibrary/MySwiftClass.swift

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+public class MySwiftClass {
+  let x: Int64
+  let y: Int64
+
+  public static func method() {
+    p("Hello from static method in a class!")
+  }
+
+  public init(x: Int64, y: Int64) {
+    self.x = x
+    self.y = y
+    p("\(self)")
+  }
+
+  public init() {
+    self.x = 10
+    self.y = 5
+  }
+
+  deinit {
+    p("deinit called!")
+  }
+}

Samples/JExtractJNISampleApp/build.gradle

@@ -156,6 +156,11 @@ dependencies {
 
 tasks.named('test', Test) {
     useJUnitPlatform()
+
+    testLogging {
+        events "failed"
+        exceptionFormat "full"
+    }
 }
 
 application {

Samples/JExtractJNISampleApp/ci-validate.sh

@@ -3,4 +3,5 @@
 set -x
 set -e
 
-./gradlew run
+./gradlew run
+./gradlew test

Samples/JExtractJNISampleApp/src/main/java/com/example/swift/HelloJava2SwiftJNI.java

@@ -40,6 +40,11 @@ static void examples() {
         long i = MySwiftLibrary.globalMakeInt();
         SwiftKit.trace("globalMakeInt() = " + i);
 
+        MySwiftClass.method();
+
+        MySwiftClass myClass = MySwiftClass.init(10, 5);
+        MySwiftClass myClass2 = MySwiftClass.init();
+
         System.out.println("DONE.");
     }
 }

Samples/JExtractJNISampleApp/src/test/java/com/example/swift/MySwiftClassTest.java

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+package com.example.swift;
+
+import com.example.swift.MySwiftLibrary;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class MySwiftClassTest {
+    @Test
+    void init_noParameters() {
+        MySwiftClass c = MySwiftClass.init();
+        assertNotNull(c);
+    }
+
+    @Test
+    void init_withParameters() {
+        MySwiftClass c = MySwiftClass.init(1337, 42);
+        assertNotNull(c);
+    }
+
+}

Samples/JExtractJNISampleApp/src/test/java/com/example/swift/MySwiftLibraryTest.java

@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+package com.example.swift;
+
+import com.example.swift.MySwiftLibrary;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.concurrent.CountDownLatch;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class MySwiftLibraryTest {
+    @Test
+    void call_helloWorld() {
+        MySwiftLibrary.helloWorld();
+    }
+
+    @Test
+    void call_globalTakeInt() {
+        MySwiftLibrary.globalTakeInt(12);
+    }
+
+    @Test
+    void call_globalMakeInt() {
+        long i = MySwiftLibrary.globalMakeInt();
+        assertEquals(42, i);
+    }
+
+    @Test
+    void call_globalTakeIntInt() {
+        MySwiftLibrary.globalTakeIntInt(1337, 42);
+    }
+
+    @Test
+    void call_writeString_jextract() {
+        var string = "Hello Swift!";
+        long reply = MySwiftLibrary.globalWriteString(string);
+
+        assertEquals(string.length(), reply);
+    }
+}

Sources/JExtractSwiftLib/Convenience/JavaType+Extensions.swift

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import JavaTypes
+
+extension JavaType {
+  var jniTypeSignature: String {
+    switch self {
+    case .boolean: "Z"
+    case .byte: "B"
+    case .char: "C"
+    case .short: "S"
+    case .int: "I"
+    case .long: "J"
+    case .float: "F"
+    case .double: "D"
+    case .class(let package, let name):
+      if let package {
+        "L\(package.replacingOccurrences(of: ".", with: "/"))/\(name);"
+      } else {
+        "L\(name);"
+      }
+    case .array(let javaType): "[\(javaType.jniTypeSignature)"
+    case .void: fatalError("There is no type signature for 'void'")
+    }
+  }
+}

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -439,7 +439,7 @@ extension FFMSwift2JavaGenerator {
   }
 }
 
-extension JavaConversionStep {
+extension FFMSwift2JavaGenerator.JavaConversionStep {
   /// Whether the conversion uses SwiftArena.
   var requiresSwiftArena: Bool {
     switch self {