How to include 'jni.h' file using CMake [duplicate] - c++

Question

This question already has answers here:
How to use FIND_JNI on cmake
(2 answers)
Closed 9 months ago.
I am trying to compile my C++ project using CMake on my Mac M1 Pro 12.0.1.
This is my simple directory structure:
In my foo.cpp, I am including jni.h header file:
#include <iostream>
#include "foo.h"
#include <vector>
#include <jni.h>
void foo()
{
std::cout << "Hello World!\n";
}
This is my CMakeLists.txt:
cmake_minimum_required(VERSION 3.4.1)
project("myapplication")
add_library(my_app SHARED main.cpp foo.cpp)
target_include_directories(my_app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
if(APPLE)
set(JAVA_INCLUDE_PATH "$ENV{JAVA_HOME}/include")
set(JAVA_INCLUDE_PATH2 "$ENV{JAVA_HOME}/include/darwin")
set(JAVA_AWT_INCLUDE_PATH "$ENV{JAVA_HOME}/include")
message("JAVA_INCLUDE_PATH = ${JAVA_INCLUDE_PATH}")
find_package(JNI REQUIRED)
if (JNI_FOUND)
message (STATUS "JNI_INCLUDE_DIRS=${JNI_INCLUDE_DIRS}")
message (STATUS "JNI_LIBRARIES=${JNI_LIBRARIES}")
endif()
target_include_directories(my_app PUBLIC ${JNI_INCLUDE_DIRS})
endif()
I am getting CMake output as:
-- Found JNI: /System/Library/Frameworks/JavaVM.framework
-- JNI_INCLUDE_DIRS=/Users/vmangal/Library/Java/JavaVirtualMachines/jdk1.8.0_202.jdk/Contents/Home/include;/Users/vmangal/Library/Java/JavaVirtualMachines/jdk1.8.0_202.jdk/Contents/Home/include/darwin;/Users/vmangal/Library/Java/JavaVirtualMachines/jdk1.8.0_202.jdk/Contents/Home/include
-- JNI_LIBRARIES=/System/Library/Frameworks/JavaVM.framework;/System/Library/Frameworks/JavaVM.framework
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/vmangal/my/practice/cmake/build
My JAVA_HOME environment variable is set to /Users/vmangal/Library/Java/JavaVirtualMachines/jdk1.8.0_202.jdk
But during make command, I am getting compilation error:
/Users/vmangal/my/practice/cmake/foo.cpp:4:10: fatal error: 'jni.h' file not found
#include <jni.h>
Am I missing something in CMakeLists.txt ?

Answer 1

I had a similar problem and found that when setting variables this way
set(JAVA_INCLUDE_PATH "$ENV{JAVA_HOME}/include")
i was getting wrong imports for C_INCLUDES and CXX_INCLUDES. Like this (see in CMakeFiles/my_app.dir/flags.make):
C_INCLUDES = -I/include -I/include/darwin
CXX_INCLUDES = -I/include -I/include/darwin
Which basically which meant that $ENV{JAVA_HOME} was an empty string.
After I set the full paths in CMakeLists
set(JAVA_INCLUDE_PATH /usr/local/Cellar/openjdk#17/17.0.3/libexec/openjdk.jdk/Contents/Home/include)
everything started working correctly.
So the conclusion is that if you want to run cmake and use $ENV{JAVA_HOME} – use syntax JAVA_HOME=/path/to/java/home cmake ...