JNI is a mechanism by which you can invoke method written in native language like C and C++. Native languages allow you to use a platform specific feature which is not in control of java language. For instance if you want java to interact directly with some specific type of hardware it will extremely difficult to achieve it. So you can write a C code and declare its native methods and call the same in Java.
See the rightside video on Batch Processing in Hibernate: -
