UnsatisfiedLinkError - Trying to access a DLL from Java

Question

I am trying to use the Java Native Interface (JNI) to run some C++ code from Java. I tried a simple test program to teach myself that, and it worked perfectly. However, now that I'm tackling a bigger project (A data acquisition program), I get an UnsatisfiedLinkError in the line that calls the function from the DLL.
Here is the stacktrace: Exception in thread "AWT-EventQueue-0" java.lang.Error: java.lang.reflect.Invoca
tionTargetException
        at org.jdesktop.application.ApplicationAction.actionFailed(ApplicationAc
tion.java:859)
        at org.jdesktop.application.ApplicationAction.noProxyActionPerformed(App
licationAction.java:665)
        at org.jdesktop.application.ApplicationAction.actionPerformed(Applicatio
nAction.java:698)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:19
95)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.jav
a:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:6263)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
        at java.awt.Component.processEvent(Component.java:6028)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4630)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4574
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
        at java.awt.Container.dispatchEventImpl(Container.java:2085)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Caused by: java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.jdesktop.application.ApplicationAction.noProxyActionPerformed(App
licationAction.java:662)
        ... 26 more
Caused by: java.lang.UnsatisfiedLinkError: fileiotest.dllinterface.startget()V
        at fileiotest.dllinterface.startget(Native Method)
        at fileiotest.dllinterface.start_daq(dllinterface.java:26)
        at fileiotest.FileIOTestView.startrun(FileIOTestView.java:680)
        ... 31 moreI have made sure that the DLL is in the classpath, using both the -classpath tag and by setting the PATH variable. Is something wrong with my DLL itself, perhaps?

Answer 1

Yes, I have.
I didn't include the code yet because I thought if someone had similar trouble, there might be something obvious I am overlooking and they wouldn't even need to see the code. I can provide it, however.
This is the C++ DLL
// consoledaq.cpp : Defines the entry point for the console application.
#include <windows.h>                    /* Compiler's include files's */
#include <string.h>                  
#include <stdio.h>
#include "cbw.h"
#include "stdafx.h"
#include "dllinterface.h"
#include "jni.h" //can copy or give full path
#include <math.h>
BOOL APIENTRY DllMain( HANDLE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
    return TRUE;
#define BOARD_NUM      0                /* Number of A/D board as defined with InstaCal */
#define BUF_SIZE       10048            /* Size of buffer */
#define NUM_SECS       10                /* Number of secs to collect data */
#define ADRANGE        BIP5VOLTS        /* A/D voltage range */
#define TIMER_NUM      1                /* Windows timer used by this program */
static HGLOBAL  MemHandle32;       
/* Variables for AinScan */
static unsigned short *ADValues;    /* Win32 pointer to A/D buffer */
static HGLOBAL   ADMemHandle;
static short     ADCurStatus;       /* Current status for D/A scan */
static long      ADCurCount;        /* Current count for A/D scan  */
static long      ADCurIndex;        /* Current index for A/D scan  */
int              ADOptions;
long       Count, Rate;
float      Voltage, Voltage2;
unsigned short CurValue, CurValue2;
JNIEXPORT void JNICALL
Java_daq_startget(JNIEnv *env, jobject obj)
     cbErrHandling (PRINTALL, STOPALL);  /* Set library's error handling */
     ADCurStatus = RUNNING;
     ADCurIndex = 0l;
     ADCurCount = 0l;
     /* Allocate A/D Windows buffer */
     ADMemHandle = cbWinBufAlloc ((long)BUF_SIZE);
     /* Allocate a local WIN32 buffer to hold A/D Data */
     MemHandle32 = GlobalAlloc(GMEM_FIXED | GMEM_DDESHARE, BUF_SIZE *sizeof(short));
     /* Get a 32-bit pointer to the A/D WIN32 buffer */
     ADValues = (unsigned short *)GlobalLock(MemHandle32);
     /* Start up background A/D scan */
     Count = BUF_SIZE;
     Rate = BUF_SIZE / (NUM_SECS * 2);
     ADOptions = BACKGROUND | CONTINUOUS;
     cbAInScan (BOARD_NUM, 0, 1, Count, &Rate, ADRANGE, ADMemHandle, ADOptions);
JNIEXPORT void JNICALL
Java_daq_stopget(JNIEnv *env, jobject obj)
     cbStopBackground(BOARD_NUM, AIFUNCTION);  /* Stop A/D subsystem background scan */
     if (ADMemHandle)                 
          cbWinBufFree (ADMemHandle);   /* Free allocated memory */
     if (MemHandle32)
          GlobalFree (MemHandle32);
JNIEXPORT jfloatArray JNICALL
Java_daq_getpoint(JNIEnv *env, jobject obj)
     jfloatArray theArray;
     if (ADCurIndex >= 0)
          /* Copy Data from memory to 32 bit memory buffer */
          cbWinBufToArray(ADMemHandle, &ADValues[ADCurIndex], ADCurIndex ,2);
          CurValue = ADValues[ADCurIndex];
          CurValue2 = ADValues[(ADCurIndex + 1)];
     else
          CurValue = 0;
          CurValue2 = 0;
     jfloat tmp[2];
     theArray =  env->NewFloatArray(2);
     cbToEngUnits(BOARD_NUM,ADRANGE,CurValue,&Voltage);                      
     cbToEngUnits(BOARD_NUM,ADRANGE,CurValue2,&Voltage2);
     tmp[0] = Voltage;
     tmp[1] = Voltage2;
     env->SetFloatArrayRegion(theArray, 0, 2, tmp);
     return theArray;
}And this is the Java class:
* To change this template, choose Tools | Templates
* and open the template in the editor.
package fileiotest;
* @author Owner
public class dllinterface {
    public native void startget();
    public native float[] getpoint();
    public native void stopget();
    static {
     System.loadLibrary("daqdll");//This is firstJNI.DLL
     /*if generated by borland
     System.loadLibrary("firstjni");//This is firstjni.dll
    public static void start_daq()
        dllinterface DI=new dllinterface();
        DI.startget();
    public static void stop_daq()
        dllinterface DI=new dllinterface();
        DI.stopget();
    public static float[] get_data_point()
      dllinterface DI=new dllinterface();
      float newtempfloat[];
      newtempfloat = DI.getpoint();
      return newtempfloat;
}