Re: Error while creating jvm in DLL

Zig <>
Mon, 11 Feb 2008 00:51:53 -0500
Just a guess, but I believe there is currently a bug in the Java =

invocation API on Windows & Mac where a process may have at most 1 VM =

associated with it. Supposedly, on Linux this becomes 1 VM per thread, =

since threads run with seperate process IDs. Ultimately, attempting to =

invoke a new VM from within an existing VM will crash. I think this is =

caused by the same bug as =, though you=
r =

symptoms are indeed somewhat different.

If this is the case, you should be able to write your test app in anothe=
r =

language, and successfully call your ODBC driver.

Your easiest solution is probably to determine if there is a VM associat=
ed =

with the current thread's process, and if so use that VM instead of =

creating a new VM.



On Thu, 07 Feb 2008 04:31:08 -0500, Swapnil Kale <



I've written a custom odbc driver to execute some complex queries
using Tomcat Server.

MS ACCESS loads the dll (through system DSN) I created and links the
table to oracle using my odbc drier.

The problem:

Inside the dll I'm creating a jvm which talks to the tomcat server.

When I run a sample application locally it works just fine (in the
sense, the jvm gets created and connection to tomcat etc etc.)

But when I try to run it through ODBC bridge, the dll is not able to
create the JVM:

It throws an exception :

# An unexpected error has been detected by HotSpot Virtual Machine:
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x10004e86, pid=4=


# Java VM: Java HotSpot(TM) Client VM (1.5.0-b64 mixed mode)
# Problematic frame:
# C [aces_odbc_driver.dll+0x4e86]

Stack: [0x00040000,0x00080000), sp=0x0007ecf0, free space=251k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code,=

C=native code)
C [aces_odbc_driver.dll+0x4e86]
C [aces_odbc_driver.dll+0x1ad2d]
C [ODBC32.dll+0x9260]
C [ODBC32.dll+0x3004]
C [ODBC32.dll+0x2fbc]
C [ODBC32.dll+0x328f9]
C [JdbcOdbc.dll+0x4c6d]
j sun.jdbc.odbc.JdbcOdbc.driverConnect(J[B[B)V+0
j sun.jdbc.odbc.JdbcOdbc.SQLDriverConnect(JLjava/lang/String;)V+93
j sun.jdbc.odbc.JdbcOdbcConnection.initialize(Ljava/lang/String;Ljava=


j sun.jdbc.odbc.JdbcOdbcDriver.connect(Ljava/lang/String;Ljava/util/
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/util/
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/lang/
j SimpleSelect.main([Ljava/lang/String;)V+23

I' was trying to use a simple java program to test the functionality.

Here is the sample java code.

import java.sql.*;

class SimpleSelect {

      public static void main (String args[]) {
       String url = "jdbc:odbc:aptest";
       String query = "SELECT * FROM emp";

       try {

       // Load the jdbc-odbc bridge driver

       Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver");


       // Attempt to connect to a driver. Each one
       // of the registered drivers will be loaded until
       // one is found that can process this URL

       Connection con = DriverManager.getConnection (
       url, "abc", "abc");

       // If we were unable to connect, an exception
       // would have been thrown. So, if we get here,
       // we are successfully connected to the URL

<Here is the code in the myodbc dll for which the DSN is created>

**,void **,void *);

    JNI_JVMPROC ProcAdd;
    if(env == NULL || jvm == NULL)

        options[0].optionString = "-Djava.class.path="required path give=

for jars"
    // options[1].optionString = "-verbose:jni";

        vm_args.version = JNI_VERSION_1_2;
        vm_args.options = options;
        vm_args.nOptions = 1;

        vm_args.ignoreUnrecognized = JNI_TRUE;

        // JNI_GetDefaultJavaVMInitArgs(&vm_args);

  if (!getcwd(buffer, 512)) { /* returns null if path is too long */
    cout << "Path name is too long \n" ;
  else {
    cout << "Current Working Directory is " << buffer;

        cout << "\n\n**************Loading jvm.dll library****************\n=

        hinstLib = LoadLibrary("jvm.dll");

        if (hinstLib == NULL)

        cout << "\n\n**************Failed Loading jvm.dll

        ProcAdd = (JNI_JVMPROC) GetProcAddress(hinstLib,

        if(ProcAdd != NULL ) {

            cout << "------------Proc address got is : --------" << ProcAdd;

        res = (ProcAdd) (&jvm,(void**)&env,&vm_args);
        //res = JNI_CreateJavaVM(&jvm,(void**)&env,&vm_args);
        cout <<res;
        if (res < 0)
            cerr<< "\n\n Can't create Java VM FROM Swapnil" << endl;
            if (env->ExceptionOccurred())
            cout<< "Destroying JVM" << endl;

I tried using the simple way of creating the jvm also but didn't work
out. The same code works when I load the dll directly in a sample

I checked the path , environment variables as well. The only problem
is jvm is not created when I try to invoke it from dll through

Any help would be appreciated.

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