A summary of CORBA learning

What we're discussing in this appendix are the basic techniques for invoking non-Java code from a Java application. Each technology has its own advantages and disadvantages. But the main problem at the moment is that not all of these features can be found in all JVMs. Therefore, even if a Java program can invoke an intrinsic method that resides on a particular platform, it may not be appropriate for another platform with different JVMs installed.

The JNI provided by sun is flexible, simple (although it requires a lot of control over the JVM kernel), powerful, and common to most JVMs. By the time this book was finalized, Microsoft had not yet provided support for JNI, but instead provided its own j/direct (an easy way to invoke the Win32 DLL function) and RNI (particularly suited to writing efficient code, but required a deep understanding of the JVM kernel). Microsoft has also provided its own proprietary Java/com integration program. This program has powerful features and turns Java into a valid language for writing COM servers and customers. Only Microsoft's compilers and JVMs can provide support for J/direct, RNI, and java/com.

Our final study is CORBA, which enables our Java objects to communicate with other objects-regardless of where they are physically located or in which language they are implemented. CORBA is different from all the techniques mentioned above, because it is not integrated into the Java language, but instead uses the integration technology of other vendors (third parties) and asks us to buy orb from other vendors. CORBA is an interesting and common scenario, but it may not be the best solution if you just want to make calls to the operating system.