Error while creating jvm in DLL

From:
Swapnil Kale <swapnil.kale@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 7 Feb 2008 01:31:08 -0800 (PST)
Message-ID:
<7709689d-19aa-41d0-ab6f-4526644296e1@c23g2000hsa.googlegroups.com>
Hi,
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=4184,
tid=4716
#
# 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/
util/Properties;I)V+984
j sun.jdbc.odbc.JdbcOdbcDriver.connect(Ljava/lang/String;Ljava/util/
Properties;)Ljava/sql/Connection;+129
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/util/
Properties;Ljava/lang/ClassLoader;)Ljava/sql/Connection;+165
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/lang/
String;Ljava/lang/String;)Ljava/sql/Connection;+41
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.net.URL;
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");

       DriverManager.setLogStream(System.out);

       // 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>

typedef _JNI_IMPORT_OR_EXPORT_ jint (JNICALL *JNI_JVMPROC) (JavaVM
**,void **,void *);

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

        options[0].optionString = "-Djava.class.path="required path given
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
\n";
        hinstLib = LoadLibrary("jvm.dll");

        if (hinstLib == NULL)
        {

        cout << "\n\n**************Failed Loading jvm.dll
library****************\n\n";
        }

        ProcAdd = (JNI_JVMPROC) GetProcAddress(hinstLib,
"JNI_CreateJavaVM");

        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())
            {
                env->ExceptionDescribe();
                env->ExceptionClear();
            }
            cout<< "Destroying JVM" << endl;
            jvm->DestroyJavaVM();
        }
    }

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
program

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
ODBC32.dll

Any help would be appreciated.

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