Java Native Interface (JNI) in Netbeans with C/C++ and Java Hello World Sample Source Code

Hi all,

Today I configured the Netbeans IDE to work with Java Native Interface (JNI).

Pre-Requisites:

1. Java Development Kit (JDK)
2. Cygwin (or) MinGW & MSYS
3. NetBeans IDE with Java and C/C++ Bundle

Installation:

• Install JDK
• Install Cygwin (or) MinGW&MSYS
• Note: While installing please choose the destination directory name without spaces
• I have installed NetBeans IDE All Version, because I thought, I will need all the technologies. That is different approach.

Configuration:

• Set the environment variables like JAVA_HOME and PATH with Java Installation Directory and JDK bin, Cygwin/MinGW&MSYS bin directories respectively
• Cygwin/MinGW integration with NetBeans
• Configure the C/C++ with Tools MinGW bin directory, which automatically fills the corresponding compilers
• 

Source Code:

• Create a sample java application with the following detail

package javaapp1.JavaApp1;

public class JavaApp1
{
public static void main(String [] args)
{
  new JavaApp1.nativePrint();
}

private native void nativePrint();
}

• Clean and Build the java project

• In Command Prompt, Navigate to Netbeans Project Directory

• cmd> cd Netbeans/ProjectDir

• Create the Java header file

• cmd> javah -o JavaApp1.h -classpath JavaApp1\build\classes javaapp1.JavaApp1

• Create a C/C++ Dynamic Library Project in Netbeans (In this example, it is CppDll1)

• Change some of the project properties

• Make sure that, you have downloaded and configured the proper Cygwin/MinGW with exact Architecture 32bit/64bit

•  Make sure that you are using proper gcc for 32bit/64bit dll creation

• Linker must be of same architecture, 32bit/64bit

• Include the Java header file, which we have created in Java Project.

• Right click on the "Source Files"-> Select "Add an Existing Item"

• Select the created header file from Project Home Directory
• (OR)
• Manually copy the created header file from Project home directory to CppDll directory

• Create a C Source file in "Source Files" in CppDll1 project

 #include "JavaApp1.h"

JNIEXPORT void JNICALL Java_javaapp1_JavaApp1_nativePrint(JNIEnv *env, jobject obj)
{
    printf("\nHello World from C\n");  
}

• Clean and Build the C code. I have faced the following issue.

• Issues Faced:

• I am using Windows 7 64-bit and installed Jdk 64-bit. But initially I have installed MinGW 32 bit and it is generating only 32 bit DLL which is not suitable to run the Java application in NetBeans.

• Resolution:

• Downloaded MinGW 64 bit and configured in the NetBeans C/C++ Options

• Copy the .dll file path

• In Java project, open the main class and add the following content

package javaapp1.JavaApp1;

public class JavaApp1
{
static
{
  System.load("dll file path");
}
public static void main(String [] args)
{
  new JavaApp1.nativePrint();
}

private native void nativePrint();
}

• Clean and Build the project

• Run the Java project to see the final JNI output.

References:
http://java.sun.com/docs/books/jni/html/jniTOC.html
http://java.sun.com/developer/onlineTraining/Programming/JDCBook/jni.html
http://www.cygwin.com/
http://sourceforge.net/projects/mingw-w64/
http://netbeans.org/community/releases/71/install.html

Please send your feedback to psrdotcom@gmail.com