Error while creating jvm in DLL

[Swapnil Kale]

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/StringV+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/
PropertiesLjava/sql/Connection;+129
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/util/
Properties;Ljava/lang/ClassLoaderLjava/sql/Connection;+165
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/lang/
String;Ljava/lang/StringLjava/sql/Connection;+41
j SimpleSelect.main([Ljava/lang/StringV+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 = "jdbcdbc: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.

 

[Zig]

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
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6587166, though your
symptoms are indeed somewhat different.

If this is the case, you should be able to write your test app in another
language, and successfully call your ODBC driver.

Your easiest solution is probably to determine if there is a VM associated
with the current thread's process, and if so use that VM instead of
creating a new VM.

HTH,

-Zig

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/StringV+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/
PropertiesLjava/sql/Connection;+129
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/util/
Properties;Ljava/lang/ClassLoaderLjava/sql/Connection;+165
j java.sql.DriverManager.getConnection(Ljava/lang/String;Ljava/lang/
String;Ljava/lang/StringLjava/sql/Connection;+41
j SimpleSelect.main([Ljava/lang/StringV+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 = "jdbcdbc: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.