结合使用Java和JNA中的C ++ DLL [英] Use C++ DLL from Java with JNA
问题描述
我尝试通过JNA使用C ++中的DLL与Java程序的Fanuc数字控件进行通信,但始终会收到以下错误消息: 线程主"中的异常java.lang.Error:无效的内存访问
I try to use a DLL from C++ with JNA to communicate with a Fanuc numeric control, from a Java program but always get this error: Exception in thread "main" java.lang.Error: Invalid memory access
我尝试使用的特定C ++方法是此 https://www.inventcom.net/fanuc-focas-library/handle/cnc_allclibhndl3
The specific C++ method that I tried to use is this https://www.inventcom.net/fanuc-focas-library/handle/cnc_allclibhndl3
FWLIBAPI short WINAPI cnc_allclibhndl3(const char *ipaddr, unsigned short port, long timeout, unsigned short *FlibHndl);
在Java的声明中,我使用以下代码:
And in the declaration in Java I use this:
short cnc_allclibhndl3(String ipaddr, short port, NativeLong timeout, short FlibHndl);
我尝试使用不同的类型映射,但始终会遇到相同的错误.
I tried with different type mappings but always get the same error.
您能告诉我此声明是否正确吗?
Can you tell me if this declaration is correct?
这是我的最后一个程序:
This is my last program:
import com.sun.jna.Library;
import com.sun.jna.Native;
public class JnaFanuc {
public interface Fwlib32 extends Library {
short cnc_allclibhndl3(String ipaddr, short port, long timeout, short FlibHndl);
}
public static void main(String[] args) {
short p = 0;
int handle = 0;
short ret;
Fwlib32 fwl = (Fwlib32) Native.load("Fwlib32", Fwlib32.class);
ret = fwl.cnc_allclibhndl3("192.168.1.100", (short)8193, 10, p);
System.out.println("cnc_allclibhndl3 Ret: " + ret);
System.out.println("hndl: " + handle);
}
}
在Daniel Widdis响应后进行编辑.
EDIT AFTER Daniel Widdis RESPONSE.
您好,我尝试了您的解决方案,这是我第一次工作.应用程序以"ret = -16"响应,这意味着"EW_SOCKET(-16)套接字错误".这是正常的,因为另一侧没有任何CNC. 当我用真实IP连接真实CNC时出现问题,然后出现与第一次相同的错误.
Hello, I tried your solution and for the first time I work. The application responds with "ret = -16" which means "EW_SOCKET (-16) Socket error". It is normal, for not having any CNC on the other side. The problem appears when I connect a real CNC with real IP, then appears the same error that the first time.
这是我的实际代码:
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.ptr.ShortByReference;
public class TestJNA {
public interface Fwlib32 extends Library {
Fwlib32 INSTANCE = (Fwlib32) Native.load("Fwlib32", Fwlib32.class);
short cnc_allclibhndl3(String ipaddr, short port, long timeout, ShortByReference FlibHndl);
}
public static void main(String[] args) {
ShortByReference handle = new ShortByReference((short)0);
short ret = 0;
Fwlib32 fwl = Fwlib32.INSTANCE;
ret = fwl.cnc_allclibhndl3("192.168.1.100", (short) 8193, 4, handle);
System.out.println("cnc_allclibhndl3 Ret: " + ret);
System.out.println("hndl: " + handle.getValue());
}
}
这是错误:
Exception in thread "main" java.lang.Error: Invalid memory access
at com.sun.jna.Native.invokeInt(Native Method)
at com.sun.jna.Function.invoke(Function.java:422)
at com.sun.jna.Function.invoke(Function.java:361)
at com.sun.jna.Library$Handler.invoke(Library.java:265)
at com.sun.proxy.$Proxy0.cnc_allclibhndl3(Unknown Source)
at testjna.TestJNA.main(TestJNA.java:38)
推荐答案
cnc_allclibhndl3()
函数中的最后一个参数是指向short
的指针:
The last argument in the cnc_allclibhndl3()
function is a pointer to a short
:
unsigned short *FlibHndl
So the proper mapping of that should be a ShortByReference
. That will initialize a pointer to a short
elsewhere in memory. Currently you're passing a null (0) pointer and asking the native method to access that memory!
此外,您需要在Java中将C long
变量映射到NativeLong
,而不是long
. Java long始终为64位,但是C long
随操作系统和位的不同而不同.在Windows中,实际上始终是32位,因此,如果您的代码仅用于Windows,则甚至可以使用int
,但是在一般/跨平台中,应使用NativeLong
进行该映射.
Also, you need the C long
variable mapped to NativeLong
in Java rather than long
. Java long is always 64 bit, but C long
varies based on OS and bitness. In Windows, that's actually always 32-bit so if your code is Windows-only you could even use int
, but in general/cross-platform you should be using NativeLong
for that mapping.
此外,惯例是Native.load()
调用必须在接口中作为静态INSTANCE
变量,而不是像您已经完成的那样直接内联定义.
Additionally the convention is for the Native.load()
call to be in the interface as a static INSTANCE
variable, rather than defining it inline as you've done.
尝试一下:
public class JnaFanuc {
public interface Fwlib32 extends Library {
Fwlib32 INSTANCE = (Fwlib32) Native.load("Fwlib32", Fwlib32.class);
short cnc_allclibhndl3(String ipaddr, short port, NativeLong timeout, short FlibHndl);
}
public static void main(String[] args) {
ShortByReference handle = new ShortByReference();
short ret;
String ip = "192.168.1.100";
short port = (short) 8193;
NativeLong timeout = new NativeLong(10);
Fwlib32 fwl = Fwlib32.INSTANCE;
ret = fwl.cnc_allclibhndl3(ip, port, timeout, handle);
System.out.println("cnc_allclibhndl3 Ret: " + ret);
System.out.println("hndl: " + handle.getValue());
}
}
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