findClass

FindClass is a function in the Java Native Interface (JNI) used by native code to locate a Java class. It is a member of the JNIEnv interface and returns a local reference to the requested class, which can be used with other JNI calls such as GetMethodID or GetStaticMethodID.

Signature and behavior: jclass FindClass(JNIEnv *env, const char *name); The name uses slash-separated internal form, for example "java/lang/String" or "com/example/MyClass$Inner" for nested classes. If the class cannot be found, FindClass raises a java/lang/ClassNotFoundException and returns NULL. After a successful call, the returned value is a local reference tied to the current JNI frame.

Usage considerations: The thread that calls FindClass must be attached to the JVM. In native threads not yet attached, you must attach the thread (and detach when finished) before calling JNI functions. The reference returned is a local reference; it will be released automatically when the native method returns, but if you need to keep it beyond the current frame you should create a global reference with NewGlobalRef and later delete it with DeleteGlobalRef.

Error handling: After calling FindClass, check for a NULL return and inspect exceptions with ExceptionOccurred. If an exception has been raised, you may clear it with ExceptionClear or let it propagate back to Java.

Pitfalls and tips: Class loader behavior can affect FindClass in complex environments; on some platforms you may need to obtain a specific class loader or use a helper to locate classes. Use slash notation for package names, and use '$' in the name for inner classes. When storing class references for later use, prefer a global reference to avoid premature release and resource leaks.

See also: JNI reference types, NewGlobalRef, DeleteGlobalRef, ExceptionOccurred.