Java Implant: Java Native Interface (JNI)

In your C/C++ file we must include JNI export and JNICAL libraries.
JNI compiles our code into native languages.
JNI helps us to write low level code that allows access to hardware directly.
Weekend reuse legacy code of product.
Creates an interface between the legacy code and Java so that you can build upon it.
The native keyword before a method indicates that implementation will be provided by a native code.
This keyword transforms our method into an abstract method.
We can use static or shared library while creating a native implementation program.

In static libraries all the code is included in our executable file, leading to an increase of its size.
In shared library The code used is only referenced, hence the executable needs to run in an environment that has access to all the files needed.

JNIEXPORT Void JNICALL java_com_jniapplication_JniMainApp_hello (JNIEnv*,Jobject,jstring) {
Std::count<<“Hello”<<name<<std::endl;
}

This table contains pointers in the memory to the implementation of all our native methods to help us call them from our Java code.

JNICALL ensures that our methods are available and ready to be used by the JNI framework.
Arguments passed are (JNIEnv*,Jobject,jstring)

The environment pointer (JNIENV) is passed as an argument for each native function mapped to a Java Method, it allows us to interact with the JNI Environment within the native method.
jobject is instance of our JniMainaApp class.
Jstring is actual parameter used by our hello method.

Function calls to JNI methods are expensive.
You will lose platform portability which is the main advantage of using Java.
Add an external layer of communication between the cord running in the JVM and our native code.

Source Code at javacodes/jniapplication at master · gauravmatta/javacodes (github.com)

Java Implant