I wanted to call a C++ method from Java. I rea开发者_JS百科d about JNI, but I am not getting how to get all the library files and where I should keep it in order to run the program from command line.
Is there any way to call a C++ method from Eclipse itself, because I am using it to run Java classes.
While I've used JNI-C++ bridging in the past (only a little though) - it can be a bit ugly. You might want to consider using SWIG to help you generate all the messy boiler plate code.
If JNI is too complicated you can take a look at JNA. In first case you have to create native wrapper code (in C or C++) to join Java and native (C++/C/...) code. In second case it is done at runtime (so you only need Java code + config).
I use JNR/FFI https://github.com/jnr/jnr-ffi which I have found to be faster than JNA and easier than SWIG. It's as close to JNI for speed I have found but less error prone.
I have used JNA before for simple interfaces and it was simple and elegant enough. It is advised though, that if there is a complex interface then it's better to use SWIG.
There are some good answers that compare SWIG with JNI and JNA. It's a while since the question was asked though.
SWIG vs JNI and JNA
JavaCPP - https://github.com/bytedeco/javacpp
It provides efficient access to native C++ inside Java. Under the hood, it uses JNI, so it works with all implementations of Java SE.
Much easier than JNA/JNI
Call c++ code from java program.
Follow the below Step
- write java code
- that contian declaration of native methods
- load shared library contain native code
- call native method
public class Sample1
{
public native int intMethod(int n);
public static void main(String[] args)
{
System.loadLibrary("Sample1");
Sample1 sample = new Sample1();
int square = sample.intMethod(5);
System.out.println("intMethod: " + square);
}
}
- Compile java code
javac Sample2.java
- create c++ header file
javac Sample2.java
- Write c++ code
#include "Sample1.h"
#include <string.h>
JNIEXPORT jint JNICALL Java_Sample1_intMethod
(JNIEnv *env, jobject obj, jint num) {
return num * num;
}
void main(){}
- compile c++ code
cc -G Sample1.c -o Sample1.so
- Run java program
java Sample1
JNA can be used instead of JNI .
All you need is to download JNA jar( https://github.com/java-native-access/jna#download ) Which should be included in your java project.
You need to give the location of your c++ library in your project properties.
- Right click project
- Run
- In VM options include this -Djava.library.path="C:Your dll location".
Visit this site for an example which also has a source code for Java and c++ project to know how this works. ( http://blog.mwrobel.eu/how-to-call-dll-methods-from-java/#a_downloads )
How to call a C/C++ function from Java then you can use Java Native Interface (JNI), part of the Java platform, is an interface that enables communication between Java applications running on a Java Virtual Machine (JVM) and native applications or libraries written in other programming languages (e.g. C, C++). You can use some below URLs for as examples.
http://malinsky.eu/blog/how-to-call-a-c-function-from-java/ https://www3.ntu.edu.sg/home/ehchua/programming/java/JavaNativeInterface.html
精彩评论