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Fix UTF-8 JniType class lookup fallback #1407

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Merged
jonathanpeppers merged 9 commits into from
Apr 17, 2026
Merged

Fix UTF-8 JniType class lookup fallback #1407

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fd27cca
Fix UTF-8 JniType class lookup fallback
simonrozsival Apr 17, 2026
ae5f5f8
Use NewStringUTF in UTF-8 class fallback
simonrozsival Apr 17, 2026
9fe9c9f
Address Copilot review feedback
simonrozsival Apr 17, 2026
f3bbd31
Unify JniType fallback helper
simonrozsival Apr 17, 2026
fb21aca
Inline UTF-8 fallback callsite
simonrozsival Apr 17, 2026
189ac79
Remove leftover UTF-8 wrapper
simonrozsival Apr 17, 2026
7e7dc88
Inline NewStringUTF call
simonrozsival Apr 17, 2026
e305f12
Move not-found throw to callsites
simonrozsival Apr 17, 2026
498fbf4
Inline UTF-8 classname decode
simonrozsival Apr 17, 2026
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144 changes: 99 additions & 45 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 @@ -3,8 +3,9 @@
using System;
using System.Diagnostics;
using System.Collections.Generic;
using System.Text;
using System.Runtime.ExceptionServices;
using System.Runtime.InteropServices;
using System.Text;

namespace Java.Interop
{
Expand Down Expand Up @@ -56,43 +57,17 @@ static unsafe JniObjectReference TryFindClass (string classname, bool throwOnErr
return r;
}
RawExceptionClear (info.EnvironmentPointer);

var findClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (findClassThrown);
var pendingException = info.Runtime.GetExceptionForThrowable (ref findClassThrown, JniObjectReferenceOptions.CopyAndDispose);

if (Class_forName.IsValid) {
var java = info.ToJavaName (classname);
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 = RawCallStaticObjectMethodA (info.EnvironmentPointer, out thrown, Class_reference.Handle, Class_forName.ID, (IntPtr) __args);
var java = info.ToJavaName (classname);
try {
if (TryLoadClassWithFallback (info, thrown, java, throwOnError, out var result))
return result;
} finally {
JniObjectReference.Dispose (ref java);
if (thrown == IntPtr.Zero) {
(pendingException as IJavaPeerable)?.Dispose ();
var r = new JniObjectReference (c, JniObjectReferenceType.Local);
JniEnvironment.LogCreateLocalRef (r);
return r;
}
RawExceptionClear (info.EnvironmentPointer);

if (pendingException != null) {
JniEnvironment.References.RawDeleteLocalRef (info.EnvironmentPointer, thrown);
}
else {
var loadClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (loadClassThrown);
pendingException = info.Runtime.GetExceptionForThrowable (ref loadClassThrown, JniObjectReferenceOptions.CopyAndDispose);
}
}

if (!throwOnError) {
(pendingException as IJavaPeerable)?.Dispose ();
if (!throwOnError)
return default;
}
throw pendingException!;

throw new InvalidOperationException ($"Could not find Java class '{classname}'.");
#endif // !(FEATURE_JNIENVIRONMENT_JI_PINVOKES || FEATURE_JNIENVIRONMENT_JI_FUNCTION_POINTERS)
#if FEATURE_JNIOBJECTREFERENCE_SAFEHANDLES
var c = info.Invoker.FindClass (info.EnvironmentPointer, classname);
Expand Down Expand Up @@ -135,6 +110,78 @@ static unsafe JniObjectReference TryFindClass (string classname, bool throwOnErr
#endif // !FEATURE_JNIOBJECTREFERENCE_SAFEHANDLES
}

static unsafe bool TryLoadClassWithFallback (JniEnvironmentInfo info, IntPtr thrown, JniObjectReference classNameJavaString, bool throwOnError, out JniObjectReference result)
{
result = default;

var findClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (findClassThrown);
Exception? pendingException = info.Runtime.GetExceptionForThrowable (ref findClassThrown, JniObjectReferenceOptions.CopyAndDispose);

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

var c = RawCallStaticObjectMethodA (info.EnvironmentPointer, out thrown, Class_reference.Handle, Class_forName.ID, (IntPtr) __args);
if (thrown == IntPtr.Zero) {
(pendingException as IJavaPeerable)?.Dispose ();
result = new JniObjectReference (c, JniObjectReferenceType.Local);
JniEnvironment.LogCreateLocalRef (result);
return true;
}
RawExceptionClear (info.EnvironmentPointer);

if (pendingException != null) {
JniEnvironment.References.RawDeleteLocalRef (info.EnvironmentPointer, thrown);
} else {
var loadClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (loadClassThrown);
pendingException = info.Runtime.GetExceptionForThrowable (ref loadClassThrown, JniObjectReferenceOptions.CopyAndDispose);
}
}

if (!throwOnError) {
(pendingException as IJavaPeerable)?.Dispose ();
return false;
}
if (pendingException != null)
throw pendingException;

return false;
}

#if FEATURE_JNIENVIRONMENT_JI_FUNCTION_POINTERS
static unsafe JniObjectReference NewJavaNameFromUtf8 (IntPtr env, ReadOnlySpan<byte> classname)
{
var terminator = classname.IndexOf ((byte) 0);
if (terminator >= 0)
classname = classname.Slice (0, terminator);

// Class names here are binary/JNI names, so `NewStringUTF()` lets the fallback
// avoid a managed UTF-16 allocation while still calling `Class.forName()`.
Span<byte> javaName = classname.Length + 1 <= 256
? stackalloc byte [classname.Length + 1]
: new byte [classname.Length + 1];

for (int i = 0; i < classname.Length; ++i)
javaName [i] = classname [i] == (byte) '/' ? (byte) '.' : classname [i];
javaName [classname.Length] = 0;

fixed (byte* pJavaName = javaName) {
var s = (*((JNIEnv**) env))->NewStringUTF (env, (IntPtr) pJavaName);
var e = JniEnvironment.GetExceptionForLastThrowable ();
if (e != null)
ExceptionDispatchInfo.Capture (e).Throw ();

var r = new JniObjectReference (s, JniObjectReferenceType.Local);
JniEnvironment.LogCreateLocalRef (r);
return r;
}
}
#endif

static bool TryRawFindClass (IntPtr env, string classname, out IntPtr klass, out IntPtr thrown)
{
#if FEATURE_JNIENVIRONMENT_JI_PINVOKES
Expand Down Expand Up @@ -331,6 +378,9 @@ public static unsafe bool TryFindClass (ReadOnlySpan<byte> classname, out JniObj

static unsafe JniObjectReference TryFindClass (ReadOnlySpan<byte> classname, bool throwOnError)
{
if (classname.Length == 0)
throw new ArgumentException ("'classname' cannot be a zero-length string.", nameof (classname));

var info = JniEnvironment.CurrentInfo;
fixed (byte* _classname_ptr = classname) {
var c = JniNativeMethods.FindClass (info.EnvironmentPointer, (IntPtr) _classname_ptr);
Expand All @@ -342,20 +392,24 @@ static unsafe JniObjectReference TryFindClass (ReadOnlySpan<byte> classname, boo
}

RawExceptionClear (info.EnvironmentPointer);

var findClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (findClassThrown);
var pendingException = info.Runtime.GetExceptionForThrowable (ref findClassThrown, JniObjectReferenceOptions.CopyAndDispose);

if (!throwOnError) {
(pendingException as IJavaPeerable)?.Dispose ();
return default;
var javaName = NewJavaNameFromUtf8 (info.EnvironmentPointer, classname);
try {
if (TryLoadClassWithFallback (info, thrown, javaName, throwOnError, out var result))
return result;
} finally {
JniObjectReference.Dispose (ref javaName);
}
throw pendingException!;
if (!throwOnError)
return default;

var terminator = classname.IndexOf ((byte) 0);
var errorClassName = terminator >= 0
? Encoding.UTF8.GetString (classname.Slice (0, terminator))
: Encoding.UTF8.GetString (classname);
throw new InvalidOperationException ($"Could not find Java class '{errorClassName}'.");
}
}
#endif // FEATURE_JNIENVIRONMENT_JI_FUNCTION_POINTERS
}
}
}

23 changes: 23 additions & 0 deletions tests/Java.Interop-Tests/Java.Interop/JniTypeUtf8Test.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,29 @@ public void FindClass_Utf8_ReturnsValidReference ()
}
}

[Test]
public void FindClass_Utf8_UsesSameFallbackAsStringOverload ()
{
var fromString = JniEnvironment.Types.FindClass ("java.lang.Object");
var fromUtf8 = JniEnvironment.Types.FindClass ("java.lang.Object"u8);
try {
Assert.IsTrue (JniEnvironment.Types.IsSameObject (fromString, fromUtf8));
} finally {
JniObjectReference.Dispose (ref fromString);
JniObjectReference.Dispose (ref fromUtf8);
}
}

[Test]
public void Ctor_Utf8_UsesSameFallbackAsStringOverload ()
{
using (var fromString = new JniType ("java.lang.Object"))
using (var fromUtf8 = new JniType ("java.lang.Object"u8)) {
Assert.IsTrue (JniEnvironment.Types.IsSameObject (fromString.PeerReference, fromUtf8.PeerReference));
Assert.AreEqual ("java/lang/Object", fromUtf8.Name);
}
}

[Test]
public void FindClass_Utf8_ThrowsOnNotFound ()
{
Expand Down