NoClassDefFoundError when trying to return a custom Object

Question

Hi,
I'm trying to get some system memory info from a Windows machine using Java. I've written the C code and Java code and it all compiles fine. I can also use most of the methods in the two files. I have a problem with one method though. Its a method that is returning an object type that I created that mirrors a windows structure. Below is the code.
// Java Object to store the data
package agent.win32;
public class MemoryInfo{
  int dwLength;
  int dwMemoryLoad;
  int dwTotalPhys;
  int dwAvailPhys;
  int dwTotalPageFile;
  int dwAvailPageFile;
  int dwTotalVirtual;
  int dwAvailVirtual;
  public int get_dwLength() { return dwLength; }
  public int get_dwMemoryLoad() { return dwMemoryLoad; }
  public int get_dwTotalPhys() { return dwTotalPhys; }
  public int get_dwAvailPhys() { return dwAvailPhys; }
  public int get_dwTotalPageFile() { return dwTotalPageFile; }
  public int get_dwAvailPageFile() { return dwAvailPageFile; }
  public int get_dwTotalVirtual() { return dwTotalVirtual; }
  public int get_dwAvailVirtual() { return dwAvailVirtual; }
// Java Class that uses JNI
package agent.win32;
public class NIMSNT {
  //Constructor
  public NIMSNT(){};
  static{
    try{
      System.loadLibrary("NIMSNT");
    catch (java.lang.UnsatisfiedLinkError e) {
      System.out.println (e);
   * check psapi.dll and psapi functions
   * return true if NT process can be enumerate
  public static native boolean Initialize();
   * Description:The EnumProcesses function retrieves the process identifier
   * for each process object in the system
   * return value:the list of process identifiers
   * call psapi function EnumProcesses
  public static native int[] EnumProcesses();
   * Description:The OpenProcess function returns a handle to an existing process object.
   * return value:If the function succeeds, the return value is an open handle to the specified process
   * call kernel32 function OpenProcess
  public static native int OpenProcess(int Pid);
   * Description:The EnumProcessModules function retrieves a handle for each module in the specified process
   * return value:the list of module handles
   * call psapi function EnumProcessModules
  public static native int[] EnumProcessModules(int hProcess);
   * Description:The GetModuleFileNameEx function retrieves the fully qualified path for the specified module
   * return value:the fully qualified path for the specified module
   * call psapi function GetModuleFileNameEx
  public static native String GetModuleFileName(int hProcess,int hModule);
   * Description:The GetModuleBaseName function retrieves the base name of the specified module
   * return value:the base name of the specified module
   * call psapi function GetModuleBaseName
  public static native String GetModuleBaseName(int hProcess,int hModule);
   * Description:function closes an open object handle
   * return value:true if succesfuly
   * call kernel32 function CloseHandle
  public static native boolean CloseHandle(int handle);
   * Description:function gets system memory
   * return value:String
  public static native MemoryInfo GetSystemMemoryInfo();
// C Structure (defined in windows.h)
typedef struct _MEMORYSTATUS {
  DWORD dwLength;
  DWORD dwMemoryLoad;
  SIZE_T dwTotalPhys;
  SIZE_T dwAvailPhys;
  SIZE_T dwTotalPageFile;
  SIZE_T dwAvailPageFile;
  SIZE_T dwTotalVirtual;
  SIZE_T dwAvailVirtual;
} MEMORYSTATUS, *LPMEMORYSTATUS;
// C code
#include <windows.h>
#include <string.h>
#include "agent_win32_NIMSNT.h"
#define MaxProcessNumber 10000
/** Type Definitions                                  **/
typedef BOOL (WINAPI *ENUMPROCESSES)(
     DWORD * lpidProcess, 
       DWORD cb,            
       DWORD * cbNeeded     
typedef BOOL (WINAPI *ENUMPROCESSMODULES)(
     HANDLE hProcess,     
     HMODULE * lphModule, 
     DWORD cb,            
     LPDWORD lpcbNeeded   
typedef DWORD (WINAPI *GETMODULEFILENAMEEXA)(
     HANDLE hProcess,          
     HMODULE hModule,          
     LPTSTR lpstrFileName,     
     DWORD nSize               
typedef DWORD (WINAPI *GETMODULEBASENAME)(
     HANDLE hProcess,          
     HMODULE hModule,          
     LPTSTR lpstrFileName,     
     DWORD nSize               
typedef struct _PROCESS_MEMORY_COUNTERS {
    DWORD cb;
    DWORD PageFaultCount;
    DWORD PeakWorkingSetSize;
    DWORD WorkingSetSize;
    DWORD QuotaPeakPagedPoolUsage;
    DWORD QuotaPagedPoolUsage;
    DWORD QuotaPeakNonPagedPoolUsage;
    DWORD QuotaNonPagedPoolUsage;
    DWORD PagefileUsage;
    DWORD PeakPagefileUsage;
} PROCESS_MEMORY_COUNTERS, *PPROCESS_MEMORY_COUNTERS;
typedef BOOL (WINAPI *GETPROCESSMEMORYINFO)(
     HANDLE hProcess,
     PPROCESS_MEMORY_COUNTERS ppsmenCounters,
     DWORD cb
/** Global Variables                                  **/
ENUMPROCESSES EnumProcesses;
ENUMPROCESSMODULES EnumProcessModules;
GETMODULEFILENAMEEXA GetModuleFileNameExA;
GETMODULEBASENAME GetModuleBaseName;
GETPROCESSMEMORYINFO GetProcessMemoryInfo;
/** DLL Entry                                         **/
BOOL APIENTRY DllMain(HANDLE hInst, DWORD ul_reason_being_called, LPVOID lpReserved){    
     return TRUE;
* Class:     nims4_agent_win32_NIMSNT
* Method:    Initialize
* Signature: ()Z
JNIEXPORT jboolean JNICALL Java_agent_win32_NIMSNT_Initialize(JNIEnv * env,jclass clazz){
     HANDLE hpsapi=LoadLibrary("PSAPI.DLL");
     if (hpsapi==NULL) return FALSE;
     EnumProcesses=(ENUMPROCESSES)GetProcAddress((HINSTANCE)hpsapi,"EnumProcesses");
     GetModuleFileNameExA = (GETMODULEFILENAMEEXA)GetProcAddress((HINSTANCE)hpsapi, "GetModuleFileNameExA");
     GetModuleBaseName = (GETMODULEBASENAME)GetProcAddress((HINSTANCE)hpsapi, "GetModuleBaseNameA");
     EnumProcessModules = (ENUMPROCESSMODULES)GetProcAddress((HINSTANCE)hpsapi, "EnumProcessModules");
     GetProcessMemoryInfo = (GETPROCESSMEMORYINFO)GetProcAddress((HINSTANCE)hpsapi, "GetProcessMemoryInfo");
     if (
          NULL == EnumProcesses          ||
          NULL == GetModuleFileName     ||
          NULL == GetModuleBaseName     ||
          NULL == EnumProcessModules  )
        return FALSE;
     return TRUE;   
* Class:     nims4_agent_win32_NIMSNT
* Method:    EnumProcesses
* Signature: ()[I
JNIEXPORT jintArray JNICALL Java_agent_win32_NIMSNT_EnumProcesses(JNIEnv * env, jclass clazz){
     DWORD aPids[MaxProcessNumber];
     DWORD cGot;
     jintArray Pids=0;
     if(EnumProcesses(aPids,sizeof(aPids),&cGot)){
          cGot /= sizeof(aPids[0]);
             Pids= (*env)->NewIntArray(env,cGot);
          (*env)->SetIntArrayRegion(env,Pids,0,cGot,(jint*) aPids);
     return Pids;
* Class:     nims4_agent_win32_NIMSNT
* Method:    OpenProcess
* Signature: (IZI)I
JNIEXPORT jint JNICALL Java_agent_win32_NIMSNT_OpenProcess (JNIEnv * env, jclass clazz,jint Pid){
     return (jint) OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ,FALSE,Pid);
* Class:     nims4_agent_win32_NIMSNT
* Method:    EnumProcessModules
* Signature: (I[I)[I
JNIEXPORT jintArray JNICALL Java_agent_win32_NIMSNT_EnumProcessModules (JNIEnv * env, jclass clazz, jint hProcess){
     HMODULE hModule[MaxProcessNumber];
     jintArray jModule=0;
     DWORD cGot;    
     if (EnumProcessModules((HANDLE)hProcess,hModule,sizeof(hModule),&cGot)){
          cGot/= sizeof(hModule[0]);
          jModule= (*env)->NewIntArray(env,cGot);
          (*env)->SetIntArrayRegion(env,jModule,0,cGot,(jint*)hModule);
     return jModule;
* Class:     nims4_agent_win32_NIMSNT
* Method:    GetModuleFileName
* Signature: (II)Ljava/lang/String;
JNIEXPORT jstring JNICALL Java_agent_win32_NIMSNT_GetModuleFileName(JNIEnv * env, jclass clazz, jint hProcess, jint hModule){
     jstring jName=0;
     char FileName[MAX_PATH];
     if(GetModuleFileNameExA((HANDLE)hProcess,(HMODULE)hModule,FileName,sizeof(FileName))!=0){
          jName=(*env)->NewStringUTF(env,FileName);
     return jName;
* Class:     nims4_agent_win32_NIMSNT
* Method:    GetModuleBaseName
* Signature: (II)Ljava/lang/String;
JNIEXPORT jstring JNICALL Java_agent_win32_NIMSNT_GetModuleBaseName(JNIEnv * env, jclass clazz, jint hProcess, jint hModule){
     jstring jName=0;
     char FileName[MAX_PATH];
     if(GetModuleBaseName((HANDLE)hProcess,(HMODULE)hModule,FileName,sizeof(FileName))!=0){
          jName=(*env)->NewStringUTF(env,FileName);
     return jName;
* Class:     nims4_agent_win32_NIMSNT
* Method:    CloseHandle
* Signature: (I)Z
JNIEXPORT jboolean JNICALL Java_agent_win32_NIMSNT_CloseHandle(JNIEnv * env, jclass clazz, jint handle)
     return CloseHandle((HANDLE) handle);
* Class:     nims_agent_win32_NIMSNT
* Method:    GetSystemMemoryInfo
* Signature: (I)Lagent/win32/MemoryInfo;
JNIEXPORT jobject JNICALL Java_agent_win32_NIMSNT_GetSystemMemoryInfo(JNIEnv * env, jclass clazz){
     jfieldID jfield;
     jobject jobj=0;
     MEMORYSTATUS stat;
     stat.dwLength = sizeof(stat);
     GlobalMemoryStatus(&stat);
     clazz=(*env)->FindClass(env,"agent.win32.NIMSMemoryInfo");
     if (clazz==0) return 0;
     jobj = (*env)->AllocObject (env,clazz);
     //set NIMSMemoryInfo object field
     // dwLength
     jfield=(*env)->GetFieldID(env,clazz,"dwLength","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwLength);
     // dwMemoryLoad
     jfield=(*env)->GetFieldID(env,clazz,"dwMemoryLoad","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwMemoryLoad);
     // dwTotalPhys
     jfield=(*env)->GetFieldID(env,clazz,"dwTotalPhys","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwTotalPhys);
     // dwAvailPhys
     jfield=(*env)->GetFieldID(env,clazz,"dwAvailPhys","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwAvailPhys);
     // dwTotalPageFile
     jfield=(*env)->GetFieldID(env,clazz,"dwTotalPageFile","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwTotalPageFile);
     // dwAvailPageFile
     jfield=(*env)->GetFieldID(env,clazz,"dwAvailPageFile","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwAvailPageFile);
     // dwTotalVirtual
     jfield=(*env)->GetFieldID(env,clazz,"dwTotalVirtual","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwTotalVirtual);
     // dwAvailVirtual
     jfield=(*env)->GetFieldID(env,clazz,"dwAvailVirtual","I");
     (*env)->SetIntField (env,jobj, jfield,stat.dwAvailVirtual);
     return jobj;
};I can use all of the methods in the Java/C code except for the the last native method   public static native MemoryInfo GetSystemMemoryInfo(); . I get a NoClassDefFoundError when I try to use this method. I have a feeling that I'm just doing something stupid.
Thanks in advance,
John

Answer 1

Yes, exactly. I changed the name of that class and forgot to change it in the c code. Thanks for the feedback.
Also, if anyone is using this code as an example, you need to change "agent.win32.MemoryInfo" to "agent/win32/MemoryInfo" in the c code. If it is left as "agent.win32.MemoryInfo" you will get a ClassCircularityError when trying to make multiple calls to the NIMSNT.GetSystemMemoryInfo();.