调用dll函数java [英] calling dll function java

问题描述

我是java的新手，我有第三方dll用于在led显示屏中显示数据。

i试图调用存在于dll中的SendColorTp（）函数我的代码是dll.i试图在java中使用system.load（）加载dll，但它显示异常java.lang.UnsatisfiedLinkError：led_data_send.SendColorTp（IIIILjava / lang / String; IIII）I

请给出一个从java调用dll的正确方法..

解决方案

我建​​议Java Native Access（JNA）比使用JNI更容易。

请找一个例子（来自维基百科）：

 import com.sun.jna.Library; 
 import com.sun.jna.Native; 
 
  / *   * Windows本机库声明和用法的简单示例。 * /  
  public   class  BeepExampl {
  public   interface  Kernel32扩展了库{
  //   FREQUENCY以赫兹表示，范围从37到32767  
  //   DURATION以毫秒表示 
  public  boolean Beep（ int  FREQUENCY， int  DURATION）; 
  public   void 睡眠（ int  DURATION）; 
} 
  public   static   void  main（ String  [] args）{
 Kernel32 lib =（Kernel32）Native.loadLibrary（   kernel32，
 Kernel32。 class ）; 
 lib.Beep（ 698 ， 500 ）; 
 lib.Sleep（ 500 ）; 
 lib.Beep（ 698 ， 500 ）; 
} 
} 

假设你有一个带有某些功能的DLL，

创建一个java接口，它具有与DLL中的函数相同的方法签名。

例如

  public   interface  NativeExample {
 
  public   int  method1（ String  param1）; 
  public  boolean mehthod2（）; 
 
} 

以下是加载DLL的方式（假设其名称为NativeLib.dll）

 NativeExample nativeExample =（NativeExample）Native.loadLibrary（ < span class =code-string> NativeLib，NativeExample。 class ）; 

一旦你有了这个，就可以通过java方法从DLL调用方法。

`nativeExample.method（  test）;`
`naturalExample.method2（）;`

iam new to java ,i have third party dll which are used to display a data in led display.
i trying to call SendColorTp() fuction which are present in dll i dint have a code of dll.i tried to load dll using system.load() in java but it showing an exception java.lang.UnsatisfiedLinkError: led_data_send.SendColorTp(IIIILjava/lang/String;IIII)I
please give an proper way to call dll from java..

解决方案

I would recommend Java Native Access (JNA) as its easier than using JNI.
Please find an example (from Wikipedia):

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

/** Simple example of Windows native library declaration and usage. */
public class BeepExampl{
   public interface Kernel32 extends Library {
       // FREQUENCY is expressed in hertz and ranges from 37 to 32767
       // DURATION is expressed in milliseconds
       public boolean Beep(int FREQUENCY, int DURATION);
       public void Sleep(int DURATION);
   }
   public static void main(String[] args) {
    Kernel32 lib = (Kernel32) Native.loadLibrary("kernel32", 
           Kernel32.class);
    lib.Beep(698, 500);
    lib.Sleep(500);
    lib.Beep(698, 500);
   }
}

Lets say you have a DLL with some functions,
Create an java interface which has the same method signatures as the functions in DLL.
For example

public interface NativeExample{

  public int method1(String param1);
  public boolean mehthod2();

}

Now following is the way you load the DLL (assuming its name is NativeLib.dll)

NativeExample nativeExample= (NativeExample)Native.loadLibrary("NativeLib", NativeExample.class);

Once you have this, you can call the method from the DLL via java methods.

`nativeExample.method("test");`
`nativeExample.method2();`

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