Handling exceptions

Exceptions give you a way to handle errors in your application. Java™ has a clear and consistent strategy for the handling of exceptions, but C/C++ code does not. Therefore, the Java JNI does not throw an exception when it detects a fault. The JNI does not know how, or even if, the native code of an application can handle it.

The JNI specification requires exceptions to be deferred; it is the responsibility of the native code to check whether an exception has occurred. A set of JNI APIs are provided for this purpose. A JNI function with a return code always sets an error if an exception is pending. You do not need to check for exceptions if a JNI function returns success, but you must check for an exception in an error case. If you do not check, the next time you go through the JNI, the JNI code detects a pending exception and throws it. An exception can be difficult to debug if it is thrown later and, possibly, at a different point in the code from the point at which it was created.