Advantages:

Developers can take the advantage of Java platform.

Legacy code investments need not be abandoned.

Interoperability issues can be addressed

Implements two-way interface that allows java applications to invoke native code and vice versa.

Disadvantages :

It is difficult to debug runtime error in native code

Security risk is high

JVM causes down by the errors in JNI code and do not provide mechanism for recovery

Heavy weight process as all the queries use strings..