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[Java.Interop] Use Class.forName() as fallback to load Java classes #1326

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[Java.Interop] Use Class.forName() as fallback to load Java classes #1326

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b8e729f
[Java.Interop] Use `Class.forName()` as fallback to load Java classes
jonpryor Mar 19, 2025
6611420
Use Class.ForName(String, boolean, ClassLoader)
jonpryor Mar 19, 2025
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18 changes: 12 additions & 6 deletions src/Java.Interop/Java.Interop/JniEnvironment.Types.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,11 +24,15 @@ static partial class Types {
};

static readonly JniMethodInfo Class_getName;
static readonly JniMethodInfo Class_forName;
static readonly JniObjectReference Class_reference;

static Types ()
{
using (var t = new JniType ("java/lang/Class")) {
Class_reference = t.PeerReference.NewGlobalRef ();
Class_getName = t.GetInstanceMethod ("getName", "()Ljava/lang/String;");
Class_forName = t.GetStaticMethod ("forName", "(Ljava/lang/String;ZLjava/lang/ClassLoader;)Ljava/lang/Class;");
}
}

Expand Down Expand Up @@ -57,12 +61,14 @@ static unsafe JniObjectReference TryFindClass (string classname, bool throwOnErr
LogCreateLocalRef (findClassThrown);
var pendingException = info.Runtime.GetExceptionForThrowable (ref findClassThrown, JniObjectReferenceOptions.CopyAndDispose);

if (info.Runtime.ClassLoader_LoadClass != null) {
if (Class_forName.IsValid) {
var java = info.ToJavaName (classname);
var __args = stackalloc JniArgumentValue [1];
var __args = stackalloc JniArgumentValue [3];
__args [0] = new JniArgumentValue (java);
__args [1] = new JniArgumentValue (true); // initialize the class
__args [2] = new JniArgumentValue (info.Runtime.ClassLoader);

c = RawCallObjectMethodA (info.EnvironmentPointer, out thrown, info.Runtime.ClassLoader.Handle, info.Runtime.ClassLoader_LoadClass.ID, (IntPtr) __args);
c = RawCallStaticObjectMethodA (info.EnvironmentPointer, out thrown, Class_reference.Handle, Class_forName.ID, (IntPtr) __args);
JniObjectReference.Dispose (ref java);
if (thrown == IntPtr.Zero) {
(pendingException as IJavaPeerable)?.Dispose ();
Expand Down Expand Up @@ -169,12 +175,12 @@ static void RawExceptionClear (IntPtr env)
#endif // FEATURE_JNIENVIRONMENT_JI_FUNCTION_POINTERS
}

static IntPtr RawCallObjectMethodA (IntPtr env, out IntPtr thrown, IntPtr instance, IntPtr jmethodID, IntPtr args)
static IntPtr RawCallStaticObjectMethodA (IntPtr env, out IntPtr thrown, IntPtr clazz, IntPtr jmethodID, IntPtr args)
{
#if FEATURE_JNIENVIRONMENT_JI_PINVOKES
return NativeMethods.java_interop_jnienv_call_object_method_a (env, out thrown, instance, jmethodID, args);
return NativeMethods.java_interop_jnienv_call_static_object_method_a (env, out thrown, clazz, instance, jmethodID, args);
#elif FEATURE_JNIENVIRONMENT_JI_FUNCTION_POINTERS
var r = JniNativeMethods.CallObjectMethodA (env, instance, jmethodID, args);
var r = JniNativeMethods.CallStaticObjectMethodA (env, clazz, jmethodID, args);
thrown = JniNativeMethods.ExceptionOccurred (env);
return r;
#else // FEATURE_JNIENVIRONMENT_JI_FUNCTION_POINTERS
Expand Down
23 changes: 6 additions & 17 deletions src/Java.Interop/Java.Interop/JniRuntime.cs
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Expand Up @@ -59,6 +59,7 @@ public partial class CreationOptions {
public IntPtr EnvironmentPointer {get; set;}

public JniObjectReference ClassLoader {get; set;}
[Obsolete ("No longer supported; Class.forName() is now used instead")]
public IntPtr ClassLoader_LoadClass_id {get; set;}

public JniObjectReferenceManager? ObjectReferenceManager {get; set;}
Expand Down Expand Up @@ -152,7 +153,6 @@ public static void SetCurrent (JniRuntime newCurrent)
bool DestroyRuntimeOnDispose;

internal JniObjectReference ClassLoader;
internal JniMethodInfo? ClassLoader_LoadClass;

public IntPtr InvocationPointer {get; private set;}

Expand Down Expand Up @@ -206,25 +206,14 @@ protected JniRuntime (CreationOptions options)
JniEnvironment.SetEnvironmentInfo (env);

ClassLoader = options.ClassLoader;
if (options.ClassLoader_LoadClass_id != IntPtr.Zero) {
ClassLoader_LoadClass = new JniMethodInfo (options.ClassLoader_LoadClass_id, isStatic: false);
}

if (ClassLoader.IsValid) {
ClassLoader = ClassLoader.NewGlobalRef ();
}

if (!ClassLoader.IsValid || ClassLoader_LoadClass == null) {
} else {
using (var t = new JniType ("java/lang/ClassLoader")) {
if (!ClassLoader.IsValid) {
var m = t.GetStaticMethod ("getSystemClassLoader", "()Ljava/lang/ClassLoader;");
var loader = JniEnvironment.StaticMethods.CallStaticObjectMethod (t.PeerReference, m);
ClassLoader = loader.NewGlobalRef ();
JniObjectReference.Dispose (ref loader);
}
if (ClassLoader_LoadClass == null) {
ClassLoader_LoadClass = t.GetInstanceMethod ("loadClass", "(Ljava/lang/String;)Ljava/lang/Class;");
}
var m = t.GetStaticMethod ("getSystemClassLoader", "()Ljava/lang/ClassLoader;");
var loader = JniEnvironment.StaticMethods.CallStaticObjectMethod (t.PeerReference, m);
ClassLoader = loader.NewGlobalRef ();
JniObjectReference.Dispose (ref loader);
}
}

Expand Down