An Introduction to JNI using a Bottom Up Approach: Step 2

Continued from An Introduction to JNI using a Bottom Up Approach: Step 1. Note: These steps may be followed without the first step below, if you remove the two references to PrintOpenWindows in the C++ code and remove "PrintOpenWindows.cpp" from the commands to compile and run "CPPHelper.exe".

Step 2: C++ Main Function

1. Comment out the main function in "PrintOpenWindows.cpp".
   /*  Uncomment to compile and run PrintOpenWindows.exe 
   int main()
   {
       cout << "PRINT_OPEN_WINDOWS ENTRY START" << endl;
       printOpenWindowsEntryPoint();
       cout << "PRINT_OPEN_WINDOWS ENTRY FINISH" << endl;
   }
   */
2. In your working directory, add an empty file, named "CPPHelper.h"
   #ifndef _CPP_HELPER_H
   #define _CPP_HELPER_H
   
   #ifdef __cplusplus
           extern "C" {
   #endif
           void cppHelperEntryPoint();
   #ifdef __cplusplus
           }
   #endif
   
   #endif
   

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3. In your working directory, add the following code, in a file named "CPPHelper.cpp":
   #include "CPPHelper.h"
   #include "PrintOpenWindows.h" // Comment to ignore PrintOpenWindows
   #include  <iostream>
   
   using namespace std;
   
   void cppHelperExitPoint()
   {
       cout << "CPP_HELPER EXIT START" << endl;
       printOpenWindowsEntryPoint(); // Comment to ignore PrintOpenWindows
       cout << "CPP_HELPER EXIT FINISH" << endl;
   }
   
   int main()
   {
       cout << "CPP_HELPER MAIN START" << endl;
       cppHelperExitPoint();
       cout << "CPP_HELPER MAIN FINISH" << endl;
   }
   
   void cppHelperEntryPoint()
   {
       cout << "CPP_HELPER ENTRY START" << endl;
       cppHelperExitPoint(); // Comment to ignore PrintOpenWindows
       cout << "CPP_HELPER ENTRY FINISH" << endl;
   }
4. Compile the code and run "CPPHelper.exe", using the following commands:
   cd /D "C:\Users\Scott\workspace\myrepo\my-app\src\main\resources\dlls"
   
   "C:\MinGW64\bin\g++.exe" -o CPPHelper.exe CPPHelper.cpp PrintOpenWindows.cpp
   
   CPPHelper.exe
   

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Continued at An Introduction to JNI using a Bottom Up Approach: Step 3.

This post was reposted from http://scottizu.wordpress.com/2013/08/21/an-introduction-to-jni-using-a-bottom-up-approach-step-2/, originally written on August 21st, 2013.