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Summary

Thursday Mar 1st 2001

What you’ve seen in this appendix are the most common techniques to call non-Java code from a Java application. Each technique has its pros and cons, but currently the major problem is that not all of these features are available on all JVMs, so a Java program that calls native methods on a specific platform might not work on a different platform with a different JVM.

Bruce Eckel's Thinking in Java Contents | Prev | Next

What you’ve seen in this appendix are the most common techniques to call non-Java code from a Java application. Each technique has its pros and cons, but currently the major problem is that not all of these features are available on all JVMs, so a Java program that calls native methods on a specific platform might not work on a different platform with a different JVM.

Sun’s JNI is flexible, reasonably simple (although it requires a lot of control over the JVM internals), powerful, and it’s available on most JVMs, but not all. Microsoft, at the time of this writing, does not support JNI, but offers J/Direct, a simple way to call Win32 DLL functions, and RNI, which is designed for high-performance code but requires a good understanding of the JVM internals. Microsoft also offers its proprietary Java/COM integration feature, which is powerful and makes Java an interesting language for writing COM servers and clients. J/Direct, RNI, and Java/COM integration are supported only by the Microsoft compiler and JVM.

Finally, we took a look at CORBA, which allows your Java objects to talk to other objects regardless of their physical location and implementation language. CORBA is different from the techniques above because it is not integrated with the Java language, but instead uses third-party integration technology and requires that you buy a third-party ORB. CORBA is an interesting and general solution, but it might not be the best approach if you just want to make calls into the operating system.

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