[GitHub] [arrow] pitrou commented on a diff in pull request #13246: ARROW-16329: [Java][C++] Keep more context when marshalling errors through JNI

[GitBox <gi...@apache.org>]

pitrou commented on code in PR #13246:
URL: https://github.com/apache/arrow/pull/13246#discussion_r884967137


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cpp/src/jni/dataset/jni_util.cc:
##########
@@ -167,9 +167,16 @@ ReservationListenableMemoryPool::~ReservationListenableMemoryPool() {}
 
 Status CheckException(JNIEnv* env) {
   if (env->ExceptionCheck()) {
-    env->ExceptionDescribe();
+    jthrowable t = env->ExceptionOccurred();
     env->ExceptionClear();
-    return Status::Invalid("Error during calling Java code from native code");
+    jclass describer_class =
+        env->FindClass("org/apache/arrow/dataset/jni/JniExceptionDescriber");
+    jmethodID describe_method = env->GetStaticMethodID(
+        describer_class, "describe", "(Ljava/lang/Throwable;)Ljava/lang/String;");
+    std::string description = JStringToCString(
+        env, (jstring)env->CallStaticObjectMethod(describer_class, describe_method, t));
+    return Status::Invalid("Error during calling Java code from native code: " +
+                           description);

Review Comment:
   Hmm... I don't know what is possible exactly, but ideally we should:
   1) map Java exception classes to specific C++ status codes (for example a `IOException` would map to `Status::IOError` while `InvalidTypeException` would map to `Status::TypeError`)
   2) keep the Java exception object in a Java-specific `StatusDetail` subclass, just like we do [for Python exceptions](https://github.com/apache/arrow/blob/master/cpp/src/arrow/python/common.cc#L54-L139)
   
   cc @lwhite1 



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