fallback to application class loader if available

Author: madsodgaard

Sources/SwiftJava/AnyJavaObject.swift

@@ -102,23 +102,39 @@ extension AnyJavaObject {
     in environment: JNIEnvironment,
     _ body: (jclass) throws -> Result
   ) throws -> Result {
-    let resolvedClass = try environment.translatingJNIExceptions {
-      environment.interface.FindClass(
-        environment,
-        fullJavaClassNameWithSlashes
-      )
-    }!
-    return try body(resolvedClass)
+    do {
+      let resolvedClass = try environment.translatingJNIExceptions {
+        environment.interface.FindClass(
+          environment,
+          fullJavaClassNameWithSlashes
+        )
+      }!
+      return try body(resolvedClass)
+    } catch {
+      // If we are in a Java environment where we have loaded
+      // SwiftJava dynamically, we have access to the application class loader
+      // so lets try that as as a fallback
+      if let applicationClassLoader = JNI.shared?.applicationClassLoader {
+        return try _withJNIClassFromCustomClassLoader(
+          applicationClassLoader,
+          in: environment
+        ) { applicationLoadedClass in
+          return try body(applicationLoadedClass)
+        }
+      } else {
+        throw error
+      }
+    }
   }
 
   /// Retrieve the Java class for this type using a specific class loader.
   private static func _withJNIClassFromCustomClassLoader<Result>(
     _ classLoader: JavaClassLoader,
     in environment: JNIEnvironment,
-    _ body: (jclass?) throws -> Result
+    _ body: (jclass) throws -> Result
   ) throws -> Result {
-    let resolvedClass = try? classLoader.findClass(fullJavaClassName)
-    return try body(resolvedClass?.javaThis)
+    let resolvedClass = try classLoader.findClass(fullJavaClassName)
+    return try body(resolvedClass!.javaThis)
   }
 
   /// Retrieve the Java class for this type and execute body().
@@ -129,16 +145,15 @@ extension AnyJavaObject {
   ) throws -> Result {
     if let AnyJavaObjectWithCustomClassLoader = self as? AnyJavaObjectWithCustomClassLoader.Type,
        let customClassLoader = try AnyJavaObjectWithCustomClassLoader.getJavaClassLoader(in: environment) {
-      try _withJNIClassFromCustomClassLoader(customClassLoader, in: environment) { clazz in
-        guard let clazz else {
-          // If the custom class loader did not find the class
-          // let's look in the default class loader.
-          return try _withJNIClassFromDefaultClassLoader(in: environment, body)
+      do {
+        return try _withJNIClassFromCustomClassLoader(customClassLoader, in: environment) { clazz in
+          return try body(clazz)
         }
-        return try body(clazz)
+      } catch {
+        return try _withJNIClassFromDefaultClassLoader(in: environment, body)
       }
     } else {
-      try _withJNIClassFromDefaultClassLoader(in: environment, body)
+      return try _withJNIClassFromDefaultClassLoader(in: environment, body)
     }
   }
 }

Sources/SwiftJava/JNI.swift

@@ -22,7 +22,10 @@ import CSwiftJavaJNI
 /// from Java.
 package final class JNI {
   /// The shared JNI object, initialized by `JNI_OnLoad`
-  package fileprivate(set) static var shared: JNI!
+  ///
+  /// This may be `nil` in the case where `SwiftJava` is not loaded as a dynamic lib
+  /// by the Java sources.
+  package fileprivate(set) static var shared: JNI?
 
   /// The default application class loader
   package let applicationClassLoader: JavaClassLoader

Sources/SwiftJavaRuntimeSupport/_JNIMethodIDCache.swift

@@ -55,7 +55,8 @@ public final class _JNIMethodIDCache: Sendable {
       // Clear any ClassNotFound exceptions from FindClass
       environment.interface.ExceptionClear(environment)
 
-      if let javaClass = try? JNI.shared.applicationClassLoader.loadClass(
+      // OK to force unwrap, we are in a jextract environment.
+      if let javaClass = try? JNI.shared!.applicationClassLoader.loadClass(
         className.replacingOccurrences(of: "/", with: ".")
       ) {
         clazz = javaClass.javaThis

Sources/SwiftJavaRuntimeSupport/generated/JavaJNISwiftInstance.swift

@@ -20,6 +20,7 @@ public struct JavaJNISwiftInstance: AnyJavaObjectWithCustomClassLoader {
   public func memoryAddress() -> Int64
 
   public static func getJavaClassLoader(in environment: JNIEnvironment) throws -> JavaClassLoader! {
-    JNI.shared.applicationClassLoader
+    // OK to force unwrap, we are in a jextract environment.
+    JNI.shared!.applicationClassLoader
   }
 }