The Java Native Interface (JNI) - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 621

If you want only to check on the existence of a pending exception without
creating a local reference to the jthrowable exception object, the Excep-
tionCheck() function may be used. It returns JNI - TRUE if an exception is
pending and JNI - FALSE if not.
Often, after detecting an exception in native code, what you really want to do
is handle the exception in Java code by throwing your own exception, perhaps
with a bit more description about what went wrong. Or sometimes, by careful
coding, you might detect an error condition in your own native code even before
calling a JNI function that would raise an exception. In these cases, you need to
throw your own exceptions back to Java, the subject of the next section.
22.10.2 Throwing exceptions in native code
Suppose we determine, either by detecting an exception thrown by a JNI function
we called, or by our own error checking of the arguments received from the Java
side, that some of the arguments are invalid. In that case we might want to throw
a java.lang.IllegalArgumentException back to the Java code.
On the Java side, throwing an IllegalArgumentException is simple:
throw new IllegalArgumentException ( " ... " );
Throwing an exception on the native side is only slightly more complicated. The
ThrowNew() function is used to throw an exception from native code to Java.
This function takes a jclass specifying the exception class to be thrown and
a string message to include with the exception. Therefore we must first find the
jclass representing the IllegalArgumentException .Wecan find that
jclass using FindClass() , just like finding any other class:
jclass iae - cls =
jenv- > FindClass ( " java/lang/IllegalArgumentException " );
if (iae - cls == NULL)
// just give up if we can't even find the
// IllegalArgumentException class
return;
With the desired exception jclass in hand, we throw it as follows:
jenv- > ThrowNew (iae - cls,
" illegal argument detected in native code " );
The second parameter to ThrowNew() is the message to be used when con-
structing the java.lang.Exception or java.lang.Throwable object.
On the Java side, J2SE 1.4 added the ability to chain exceptions by specifying a
Throwable as a cause parameter to the Exception and Throwable construc-
tors. As of this writing, there is no simple way to provide a Throwable cause