Why You Should Use JNI in Your Project?
JNI stands for Java Native interface. It is basically used to integrate Java code with Native code like C or C++ code. In this blog, I would like to give a brief introduction to JNI, its need, alternatives to JNI, advantages, and disadvantages of JNI and some resources to study JNI in detail.
What is JNI?
JNI is used to call methods or access code written in native languages like C/C++. It is a framework or tool that helps to bridge Java with other programming languages.
When to use JNI?
Now, an important question comes and that is when to use JNI or why to use JNI. Java comes with the benefit of platform independence But sometimes it becomes necessary to write platform/architecture-specific code. Sometimes we need to use/implement hardware-specific features.
Also, sometimes we need to use existing code which is written in native code. Hence instead of writing it completely again in Java, we can use JNI to reuse it.
How JNI works?
We can create Java methods with Native keywords and its implementation is written in the Native language. We can keep Java code and Native code separate. Native code will be in a shared library which can be included in Java project to access it.
Let’s check some example below,
Step 1: Write a Java class with Method declared as Native. And use System.loadLibrary to load shared library (which will have an implementation of declared native method)
Step 2: Generate .h file using Javah, which will have a signature for a native method to be written.
Step 3: Include this .h file in Native code and write an implementation for it and publish it as a shared library.
Step 4: Include a shared library in Java code to call the native method.
Java Code for “Hello World”
C Code for “Hello World”
You can refer to the following link for a detailed description of JNI Hello world example: http://www.lithiumhead.com/notes/windows_jni
Tips to handle common errors with JNI
Common error with getting with JNI is UnsatisfiedLinkError. This error comes when JVM can not find native code (all in case of windows).
To resolve this error, please make sure that native code is in Java library path or included in the PATH variable.
Check some Other options
Below are some of the other earlier options available for integrating Java code with native code.
- RNI – Remote Native Interface by Microsoft
- JRI – Java Runtime Interface by Netscape
- COM – COM interface by Microsoft
Most of the above options are VM (Virtual Machine) specific, which means we can not write a VM independent integration with these and JNI is a better choice.
Other than the above options we have JNA (Java Native Access) which is comparable to JNI It is simpler to implement option but performance-wise it is slower.
Advantages of JNI:
- Use of platform-specific features in Java
- Can use existing code written in native languages
- Increased speed of execution
Disadvantages of JNI:
- As JNI has platform-specific code as well, Write once Run everywhere is not possible.
- JNI code is difficult to debug and knowledge of the native language is needed.
- The security risk is potential.
JNI may not be one of the simplest of technologies, but it’s undoubtedly worth getting acquainted with. If you used it once to complete a project, then surely, next time, you will never deny to use it. It helps to combine C++ and Java Java anymore. Well, if you don’t have expert developers in these programming languages, then don’t hesitate to contact us to get the Java outsourcing service. Our service can aid you to execute out-of-the-box projects in a minimal time frame.