Java Native Interface Shortcomings

High overheads
Raw method invocation overhead
Marshalling arguments, return values
Expensive array copy between Java and C

Native code is undesirable
Can't verify it stays within the "sandbox"
Native code is non-portable
Native code is error-prone
Strong separation between JVM and native methods

Can only bind native code to method invocation
No "native fields", "native operators", etc.
Limits expressivity
Too coarse-grained