JNA入门（一）

JNA入门，代码在github写得明明白白：https://github.com/java-native-access/jna/blob/master/www/GettingStarted.md

一、显示调用 kernel32.dll

首先知道kernel32.dll中获取系统时间的函数

// GetSystemTime(SYSTEMTIME result)
typedef struct _SYSTEMTIME {
  WORD wYear;
  WORD wMonth;
  WORD wDayOfWeek;
  WORD wDay;
  WORD wHour;
  WORD wMinute;
  WORD wSecond;
  WORD wMilliseconds;
} SYSTEMTIME, *PSYSTEMTIME, *LPSYSTEMTIME;

Maven

<dependency>
    <groupId>net.java.dev.jna</groupId>
    <artifactId>jna</artifactId>
    <version>5.10.0</version>
</dependency>

编写java接口，对应dll的接口

import com.sun.jna.Native;
import com.sun.jna.Structure;
import com.sun.jna.win32.StdCallLibrary;

/**
 * @author lingkang
 * @date 2021/12/20
 */
public interface Kernel32 extends StdCallLibrary {
    Kernel32 INSTANCE = (Kernel32)
            Native.load("kernel32", Kernel32.class);

    @Structure.FieldOrder({"wYear", "wMonth", "wDayOfWeek", "wDay", "wHour", "wMinute", "wSecond", "wMilliseconds"})
    public static class SYSTEMTIME extends Structure {
        public short wYear;
        public short wMonth;
        public short wDayOfWeek;
        public short wDay;
        public short wHour;
        public short wMinute;
        public short wSecond;
        public short wMilliseconds;
    }

    void GetSystemTime(SYSTEMTIME result);
}

编写调用的main方法

/**
 * @author lingkang
 * @date 2021/12/20
 */
public class Helloworld {

    public static void main(String[] args) {
        Kernel32 lib = Kernel32.INSTANCE;
        Kernel32.SYSTEMTIME time = new Kernel32.SYSTEMTIME();
        lib.GetSystemTime(time);

        System.out.println(time.wYear+"-"+time.wMonth+"-"+time.wDay);
    }
}

输出：

还有现成的依赖库：

<dependency>
    <groupId>net.java.dev.jna</groupId>
    <artifactId>jna-platform</artifactId>
    <version>5.10.0</version>
</dependency>

直接调用 Kernel32 .Dll

import com.sun.jna.platform.win32.Kernel32;

/**
 * @author lingkang
 * @date 2021/12/20
 */
public class Helloworld {

    public static void main(String[] args) {
//        Kernel32 lib = Kernel32.INSTANCE;
//        Kernel32.SYSTEMTIME time = new Kernel32.SYSTEMTIME();
//        lib.GetSystemTime(time);
//
//        System.out.println(time.wYear+"-"+time.wMonth+"-"+time.wDay);
        Kernel32 kernel32=Kernel32.INSTANCE;
        Kernel32.SYSTEMTIME time = new Kernel32.SYSTEMTIME();
        kernel32.GetSystemTime(time);
        System.out.println(time.wYear+"-"+time.wMonth+"-"+time.wDay);
    }
}