harden JNI.applicationClassLoader for cases when we're not loading libs

Author: ktoso

Samples/JavaKitSampleApp/Tests/JavaKitExampleTests/JavaKitMethodCalledInitTests.swift

@@ -21,15 +21,6 @@ import Testing
 @Suite
 struct JavaKitMethodCalledInitTests {
 
-  @Test
-  func test() throws {
-    let jvm = try JavaKitSampleJVM.shared()
-    let env = try jvm.environment()
-
-    let hello = HelloSwift(environment: env)
-    
-    let reply = hello.`init`(128)
-    #expect(reply == 128)
-  }
+  
 
 }

Samples/JavaKitSampleApp/Tests/JavaKitExampleTests/JavaKitOptionalTests.swift

@@ -21,10 +21,11 @@ import Testing
 @Suite
 struct ManglingTests {
 
+  let jvm = try JavaKitSampleJVM.shared
+
   @Test
   func methodMangling() throws {
-    let jvm = try JavaKitSampleJVM.shared()
-    let env = try! jvm.environment()
+    let env = try jvm.environment()
 
     let helper = ThreadSafeHelperClass(environment: env)
 
@@ -49,4 +50,14 @@ struct ManglingTests {
     #expect(#"Optional(21)"# == String(describing: longOpt))
   }
 
+  @Test
+  func methodNamedInit() throws {
+    let env = try jvm.environment()
+
+    let hello = HelloSwift(environment: env)
+    
+    let reply = hello.`init`(128)
+    #expect(reply == 128)
+  }
+
 }

Samples/JavaKitSampleApp/Tests/JavaKitExampleTests/JavaKitSampleJVM.swift

@@ -21,15 +21,15 @@ import JavaUtilFunction
 /// classes defined in this JavaKitExample project
 struct JavaKitSampleJVM {
 
-  static func shared() throws -> JavaVirtualMachine {
-    try JavaVirtualMachine.shared(
+  static var shared: JavaVirtualMachine = {
+    try! JavaVirtualMachine.shared(
       classpath: [
         ".build/plugins/outputs/javakitsampleapp/JavaKitExample/destination/JavaCompilerPlugin/Java",
       ],
       vmOptions: [
         KnownJavaVMOptions.javaLibraryPath(".build/\(SwiftPlatform.debugOrRelease)/"),
       ]
     )
-  }
+  }()
 
 }

Sources/SwiftJava/JNI.swift

@@ -28,15 +28,28 @@ package final class JNI {
   package fileprivate(set) static var shared: JNI?
 
   /// The default application class loader
-  package let applicationClassLoader: JavaClassLoader
+  package let applicationClassLoader: JavaClassLoader?
 
   init(fromVM javaVM: JavaVirtualMachine) {
     // Update the global JavaVM
     JavaVirtualMachine.sharedJVM.withLock {
       $0 = javaVM
     }
     let environment = try! javaVM.environment()
-    self.applicationClassLoader = try! JavaClass<JavaThread>(environment: environment).currentThread().getContextClassLoader()
+    do {
+      let clazz = try JavaClass<JavaThread>(environment: environment)
+      guard let thread: JavaThread = clazz.currentThread() else {
+        applicationClassLoader = nil
+        return 
+      }
+      guard let cl = thread.getContextClassLoader() else {
+        applicationClassLoader = nil
+        return 
+      }
+      self.applicationClassLoader = cl
+    } catch {
+      fatalError("Failed to get current thread's ContextClassLoader: \(error)")
+    }
   }
 }