JNA简单范例

• C头文件

#ifndef __JNATEST_H__
#define __JNATEST_H__

#define LOG_HERE() printf("%s-%d\n", __func__, __LINE__)

void test_jna();

#endif

• C代码

#include <stdio.h>
#include "jnatest.h"

void test_jna()
{
    LOG_HERE();
    printf("called from JAVA\n");
}

• JAVA代码

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Platform;

public class JnaTest
{
    //继承Library，用于加载库文件  
    public interface CLibrary extends Library
    {
        CLibrary INSTANCE = (CLibrary) Native.loadLibrary(
            (Platform.isWindows() ? "msvcrt" : "c"), CLibrary.class);

        // 声明一个跟C语言的printf()一样的方法，
        void printf(String format, Object... args);
    } 

    public interface TestLibrary extends Library
    {
        TestLibrary INSTANCE = (TestLibrary) Native.loadLibrary("jnatest", TestLibrary.class);

        void test_jna();
    } 


    public static void main(String[] args)
    {
        //调用  
        CLibrary.INSTANCE.printf("From JAVA To C, year=%d\n", 2022);
        TestLibrary.INSTANCE.test_jna();
    }
}

• 安装依赖库

sudo apt install -y openjdk-8-jdk
sudo apt install -y libjna-java
sudo apt install -y libjna-platform-java

• 编译

gcc -fPIC -shared -o libjnatest.so jnatest.c
sudo ldconfig

javac -extdirs /usr/share/java JnaTest.java

• 测试

USJ_DIR=/usr/share/java
CLASS_DIRS=.
CLASS_DIRS=${CLASS_DIRS}:${USJ_DIR}/jna.jar
CLASS_DIRS=${CLASS_DIRS}:${USJ_DIR}/jna-platform.jar

java  \
    -cp ${CLASS_DIRS} \
    JnaTest