Calling JVM from C++

My biggest dream at the moment is to start Java class "halllo world" from C++. Following environments are being used:Windows 2000, Visual C++ and JBuilder4.0
I�m running out of ideas and it seems to me the more I look for a solution the more contradictory informations I get. In book CORE JAVA (Sun) they say that i need jni.h .O.K. Included...They also say for windows jvm.dll library is needed..I tried it too ..I have put path to this library in all possible paths in Visual c++..Doesn�t work..I have also made include of jvm.h but then I get errors in windows.h???? on a few pages in internet (ibm..) I have found that in this case for Windows javai.lib is needed..? What�s that suppose to mean???? This library doesn`t exist in JBuilder or anywhere else.
I�m stuck with this problem for two weeks,working on my diploma and loosing nervs...So please if somebody has at least new ideas or even better knows the solution contact me...Thanks

I forgot to add what is my biggest problem: Functions as JNI_CreateJavaVM...are not being recognized..I m getting linking errors :Unresolved symbol....JNI_CreateJavaVM...and so on and so on...
Thanks again ...

Similar Messages

Calling JVM from C native code

I'd like to call JVM from C native call.
I work in W2000 enviroment using GCC Cygnus compiler.
I followed JNI instructions.
I read in this forum there was a change in JDK, and instead of attaching javai.dll, jvm.dll must be attached.
Then I made a test using invoke.c example from JDK.
I built following .bat file:
gcc -c invoke.c -Id:\jdk1.3.1\include -Id:\jdk1.3.1\include\win32
DLLTOOL dllname jvm.dll def libjvm.def --output-lib d:\jdk1.3.1\jre\bin\classic\libjvm.a
c++ -o invoke.exe invoke.o -Ld:\jdk1.3.1\jre\bin\classic -ljvm
with libjvm.def :
EXPORTS
imp_JNI_GetDefaultJavaVMInitArgs@4
imp_JNI_CreateJavaVM@12
All seems to work fine, and invoke.exe is generated. But when trying to run it, I get a windows message telling me :
invoke.exe doesn't find the entry point to imp_JNI_CreateJavaVM@12 in jvm.dll.
What am I going wrong ?
Any calling convention issue ?
Thanks in advance. Ignasi Villagrasa.

Have a look at http://www.xraylith.wisc.edu/~khan/software/gnu-win32/. It has examples of how to use gcc, java JNI on cygwin and should work on all versions of Windows. It has the command line options for using dlltool.

Calling JVM from outside

Hello!
A question of possibly not a common nature: are there any ways I can ask a JVM to run a specific Java code.
For example, when MS IE encounters an applet, it somehow instructs JVM to start up, provide an environment for applet's intercommunication with IE, and execute the applet.
How can I do the same thing in my WinXP program - i.e. to make JVM start up and execute something, possibly - applet, or a kind of bean, or...?
Or, a thinner task: there is a file 'CCC.class' with class CCC containing static member function bool LaunchAnthraxMissile(int targetX, int targetY);
Is there any way for me in my external program (possibly, in C++) to execute this function and examine a result? (without, of course, launching java interpreter with CreateProcess :) )
Thanks,
Slicer

Is there any way for me in my external program (possibly, in C++) You could use JNI.
However it is probably just easier to do a operating system call where the execution string is "java MyClass".

Calling jvm from c++ code fails the secnd time

Hi all,
i have a dll which calls java code thru jni.
for the first time i am able to successfully call the jvm.
when i execute 2nd time jvm crashes
though i destroy the jvm for the first time.
looks like it doesnot load all native method.
below i have listed the verbose of jvm loading secnd time.
please advice me if i need to use any technique in loading the jvm.
thanks in advance
[Dynamic-linking native method java.lang.Float.intBitsToFloat ... JNI]
[Dynamic-linking native method java.lang.Double.longBitsToDouble ... JNI]
[Dynamic-linking native method java.lang.Float.floatToIntBits ... JNI]
[Dynamic-linking native method java.lang.Double.doubleToLongBits ... JNI]
[Dynamic-linking native method java.lang.Object.registerNatives ... JNI]
[Registering JNI native method java.lang.Object.hashCode]
[Registering JNI native method java.lang.Object.wait]
[Registering JNI native method java.lang.Object.notify]
[Registering JNI native method java.lang.Object.notifyAll]
[Registering JNI native method java.lang.Object.clone]
[Dynamic-linking native method java.lang.Throwable.fillInStackTrace ... JNI]
# HotSpot Virtual Machine Error, Internal Error
# Please report this error at
# http://java.sun.com/cgi-bin/bugreport.cgi
# Error ID: 455843455054494F4E530E43505000DE
# Problematic Thread: prio=139238232 tid=0x84c9b58 nid=0x0 runnable
#

Hallo,
if I understand your problem correctly, you are creating the JVM, doing something, calling DestroyJavaVM() and then creating the JVM once more. You cannot do that! See: http://java.sun.com/j2se/1.3/docs/guide/jni/jni-12.html#DestroyJavaVM . The solution is just to create the JVM once, when you first need it. You can then reuse it as offen as you want.

Increase JVM heap size when calling it from C++

I have a program that loads images and only works properly increasing heap.
java McVImg
gives me an Out of memory error.
java -Xmx120M McVImg
works fine.
If I want to call JVM from a C++ program using Java native interface,
How should I increase JVM heap ?
Thanks in advance. Ignasi Villagrasa.

I'm trying to do what you told me and it doesn't work.
I show the C++ code I'm using:
void JavaParam::LoadJVM()
     JavaVMInitArgs vm_args;
     JavaVMOption options[2];
jint res;
     vm_args.version = JNI_VERSION_1_2;
JNI_GetDefaultJavaVMInitArgs(&vm_args);
     if (res < 0)
fprintf(stderr, " Requested version is not supported\n");
          fputs ("Requested version is not supported\n",traza);
          fflush(traza);
exit(-1);
     //Establecemos classpath
     //Atencion el classpath ser� el jar
     //options[0].optionString = "-Djava.class.path=..";
     options[0].optionString = "-Djava.class.path=..\\mcjava.jar";
     options[1].optionString = "-Xmx120M";
     //Nuevos argumentos
vm_args.options=options;
     vm_args.nOptions = 2;
     vm_args.ignoreUnrecognized = JNI_FALSE;
     //Creamos Maquina Virtual Java
res = JNI_CreateJavaVM(&jvm,(void **)&env,&vm_args);
if (res < 0)
fprintf(stderr, "Can't create Java VM: %d\n",(int)res);
          fprintf(traza, "Can't create Java VM RES: %d \n",(int)res);
          fflush(traza);
exit(1);
     jvm_creada = 1;
Is that right ?
Thanks in advance. Ignasi Villagrasa.

Can I Call method on one JVM from another through a dll?

Let me explain.
I have this java jar file that I can only have one instance of running at any given time. I'm using a shared data segment in a dll to store a bool indicating whether the program is already running or not. If it's already running, I have to not run the second instance and give focus to the current running instance.
The jar file calls a native method "canInstantiate()" on a dll to see if there's already an app running. If there isn't, the env and obj are stored in the shared data segment of the dll and we return true. If there is already an instance of the program running, I want canInstantiate call a function on the current instance of the jar (like a callback) to tell it to request focus. It's not working. Can someone tell me if my code is right?
The .h file
#include "stdafx.h"
#include <jni.h>
#include "CardServer.h"
#pragma data_seg("SHARED") // Begin the shared data segment.
static volatile bool instanceExists = false;
static JavaVM *theJavaVM = NULL;
static JNIEnv* theJavaEnv= NULL;
static jobject instanceObject = NULL;
static jmethodID mid = NULL;
static jclass cls = NULL;
#pragma data_seg()
#pragma comment(linker, "/section:SHARED,RWS")
jdouble canInstantiate(JNIEnv *env, jobject obj);
jdouble instantiate(JNIEnv *env, jobject obj);
jdouble uninstantiate(JNIEnv *env, jobject obj);
void grabFocus();
</code>
The .cpp file:
<code>
#include "MyFunctions.h"
#include <string.h>
#include <stdlib.h>
#include "stdafx.h"
#include <iostream.h>
jdouble canInstantiate(JNIEnv *env, jobject obj)
printf("In canInstantiate!!");
if (!instanceExists)
printf("No instance exists!!");
return (jdouble)0.0;
else
printf("An instance already exists!!");
grabFocus();
return (jdouble)1.0;
jdouble instantiate(JNIEnv *env, jobject obj)
printf("**In CPP: Instantiate!!\n");
cout << "At start, env is: " << env << endl;
cout << "At start, obj is: " << obj << endl;
if (instanceExists == false)
instanceExists = true;
theJavaEnv = env;
instanceObject = obj;
theJavaEnv->GetJavaVM(&theJavaVM);
cls = (theJavaEnv)->FindClass("TheMainClassOfTheJar");
if (cls == 0) {
fprintf(stderr, "Can't find Prog class\n");
exit(1);
mid = (theJavaEnv)->GetMethodID(cls, "grabFocusInJava", "(I)I");
if (mid == 0) {
fprintf(stderr, "Can't find grabFocusInJava\n");
exit(1);
printf("About to call grabFocusInJava\n");
grabFocus();
printf("CPP: After the grab focus command in instantiate!!\n");
cout << "At end, env is: " << env << endl;
cout << "At end, obj is: " << obj << endl;
return 0.0;
else
printf("CPP: Finished Instantiate!!\n");
return 1.0;
jdouble uninstantiate(JNIEnv *env, jobject obj)
printf("CPP: In uninstantiate!!\n");
if (instanceExists == true)
instanceExists = false;
theJavaVM = NULL;
instanceObject = NULL;
printf("CPP: Finishing uninstantiate!!\n");
return 0.0;
else
printf("CPP: Finishing uninstantiate!!\n");
return 1.0;
void grabFocus()
printf("In CPP::GrabFocus!!\n");
instanceObject = theJavaEnv->NewGlobalRef(instanceObject);
cls = (theJavaEnv)->FindClass("CardFormatter");
if (cls == 0) {
fprintf(stderr, "Can't find Prog class\n");
exit(1);
printf("Got the cls id again!!\n");
if (cls == 0)
printf("IT'S INVALID!!\n");
mid = (theJavaEnv)->GetMethodID(cls, "grabFocusInJava", "(I)I");
if (mid == 0) {
fprintf(stderr, "Can't find grabFocusInJava\n");
exit(1);
theJavaEnv->CallIntMethod(instanceObject, mid, 2);
printf("Called grabFocusInJava\n");
</code>
thanks in advance

Can I Call method on one JVM from another through a dll
...The rest of your question merely expands on your title.
And the answer to that question is no.
When you call a method you are executing a "thread of execution." A thread of execution exists only in a single process. It can not exist in another process.
If the dll is doing some interesting things then you could call a method that sets a flag. Data can move between instances. But you would then have to have a thread in that different process monitoring that flag. And sharing data in a dll is not a normal process, so it would have to be coded appropriately.
If all you want to do is set the current focus to the existing application, then that can be done with existing windows functionality. You don't need to do anything special in your dll. You can probably search these forums to find the exact code. If not there are countless examples in windows repositories (like MSDN) on how to do that.

Create JVM from my own dll

Hi all,
I'm trying to create a JVM from within a windows dlln (vc++6) I'm writing. In the DllMain's DLL_PROCESS_ATTACH method of my dll I call a method called createJavaVM, this method creates the virtual machine.
Using that method in a simple console application works ok, but using it in my dll it hangs and seems to wait forever. If I use -verbose:jni it shows 5 similar lines, all about [Dynamic linking native method java.lang.... JNI].
I'm using jdk1.5.0_04.
Can someone help me with this problem?
TiA
Alexander

see here. You will need the Pro version of LabVIEW or purchase tha application builder from NI
Paul <--Always Learning!!!
sense and simplicity.
Browse my sample VIs?

Shutting down jvm from activex bridge

How can I shut down the jvm from my bean packaged as an activex control. Calling System.exit is crashing the host as well.

All you have to do is call Activatable.inactive().I have tried calling Activatable.Inactive() to terminate the JVM without success. Instead I get an exception stating that the object is already inactive, meanwhile the JVM still lingers.
I called the Activatable.inactive from my client program, perhaps this is my problem. Should I call it from within my remote object?

Calling JPA from a Java Stored Procedure

Is it possible to call JPA from a java stored procedure? If so, does anyone have example? How do you setup the persistence.xml?
How does the peformance compare with straight JDBC in a java stored procedure?
Thanks for any help!
Johnny

Hi Johnny:
Basically you can run any JDK 1.5 framework inside your Oracle 11g JVM, I have experience integrating Lucene IR library as a new [Domain Index for Oracle 11g/10g|http://docs.google.com/View?id=ddgw7sjp_54fgj9kg] .
I am not familiar with JPA internals but my advice is howto handle the connection inside the OJVM and the configuration files.
Some time ago I took a look to SpringFramework integration and I found that writing a new ApplicationContext class which handles the loading of beans.xml from XMLDB repository instead a file should be enough to work.
Another important point is the life cycle of the [Oracle internal JVM|http://download.oracle.com/docs/cd/E11882_01/java.112/e10588/chtwo.htm#BABHGJFI]. Unlike an standard JVM the OJVM is created once you first connect from the middle tier at OCI level and remains in execution during the connection pool existence.
I mean, if you connect using a JDBC pool the JVM will remains running across multiple soft open/close connections of your middle tier application. This is good because you can read your persistence.xml file using a Singleton class and this expensive operation will be re-used by multiple open/close operation done from the middle tier.
I suggest you do a simple Proof of Concept with a Hello World application and check if it works.
Remember that any security issues will be notified to the .trc files, security issues are related to the strong security layer configured by default inside the OJVM, for example you can not read any files from the OS file system without an specific grant, you need another grant to access to the class loader and so on, but you can simply grant this specific needs to a database role and then grant this role to the user which connect to the OJVM.
Another important point is related to the [End-of-Call Optimization|http://download.oracle.com/docs/cd/E11882_01/java.112/e10588/chtwo.htm#BABIFAAI] this can be useful if you want to perform some clean up in your Singleton class at the level of per-statement execution.
Best regards, Marcelo

Calling JavaMethods from C

I have worked on JNI.In that i usually use C methods in and create a dll and use those methods in java.But i want to write my application in C and call Java methods.Is there any way to do this.Tell me step by step so that i can understand well.Thanks a lot

The Sun code sample uses JDK1_1InitArgs which is outdated.
I don't know why they kept showing this sample code in their documentation up to JDK 5.0 version.
The [url http://download.java.net/jdk6/docs/technotes/guides/jni/spec/invocation.html#wp9502]JDK 6.0 documentation is updated though.
Anyway here is an updated sample of code that starts a JVM:
[url http://www.rgagnon.com/javadetails/java-0354.html]Start JVM from C
Regards

Problem calling java from vb via activex bridge

I am trying to call java from vb via ActiveX Bridge and I am running into problems. I would appreciate any help.
I am using Visual Basic 2010 express, and Java JDK 1.6.0_16. I have used the http://download.oracle.com/javase/1.4.2/docs/guide/beans/axbridge/developerguide/index.html page as a guideline. To try to make it work I took the following steps:
1. Wrote a very simple java class (below):
package xxx;
import java.io.Serializable;
public class axb implements Serializable {
public int get_axb_Handle() {
int Address = 12345678;
return Address;
2. After I compiled, and created the jar file. I built the dll using the following command:
"C:\Program Files\Java\jdk1.6.0_16\bin\packager" -out "C:\Program Files\Java\jdk1.6.0_16\jre\axbridge\bin" E:\axb\dist\axb.jar xxx.axb
3. I then registered using: regsvr32 axb.dll
4. In Visual Basic Express IDE I use Project -> Add Reference to add Iterop.axb (dump below), and axb namespace
5. In my basic code I use the following lines
Dim axb1 As axb.axb
axb1 = New axb.axb <== Crash here with AccessViolationException ( full exception below)
What am I missing? Any help would be greatly appreciated
Thanks
Iterop.axb partial dump
___[MOD] C:\Documents and Settings\Elie A. Cohen.USINC022\My Documents\Visual Studio 2010\Projects\Repo API Example\Repo API Example\obj\x86\Release\Interop.axb.dll
| M A N I F E S T
|___[NSP] axb
| |___[INT] axb.axb
| | | .class interface public abstract auto ansi import /*02000006*/
| | | implements axb.axbDispatch/*02000003*/
| | | implements axb.axbSource_Event/*02000005*/
| | | .custom /*0C000018:0A000001*/ instance void [mscorlib/*23000001*/]System.Runtime.InteropServices.GuidAttribute/*01000002*/::.ctor(string) /* 0A000001 */ = ( 01 00 24 34 45 36 44 30 44 41 38 2D 36 41 45 44 // ..$4E6D0DA8-6AED ...
| | | .custom /*0C000019:0A000007*/ instance void [mscorlib/*23000001*/]System.Runtime.InteropServices.CoClassAttribute/*01000009*/::.ctor(class [mscorlib/*23000001*/]System.Type/*01000007*/) /* 0A000007 */ = ( 01 00 0C 61 78 62 2E 61 78 62 43 6C 61 73 73 00 // ...axb.axbClass. ...
| |
| |___[CLS] axb.axbClass
| | | .class public auto ansi import /*02000004*/
| | | implements axb.axbDispatch/*02000003*/
| | | implements axb.axb/*02000006*/
| | | implements axb.axbSource_Event/*02000005*/
| | | .custom /*0C00000F:0A000008*/ instance void [mscorlib/*23000001*/]System.Runtime.InteropServices.ClassInterfaceAttribute/*0100000A*/::.ctor(int16) /* 0A000008 */ = ( 01 00 00 00 00 00 ) ...
| | | .custom /*0C000010:0A000009*/ instance void [mscorlib/*23000001*/]System.Runtime.InteropServices.ComSourceInterfacesAttribute/*0100000B*/::.ctor(string) /* 0A000009 */ = ( 01 00 0F 61 78 62 2E 61 78 62 53 6F 75 72 63 65 // ...axb.axbSource ...
| | | .custom /*0C000011:0A000001*/ instance void [mscorlib/*23000001*/]System.Runtime.InteropServices.GuidAttribute/*01000002*/::.ctor(string) /* 0A000001 */ = ( 01 00 24 43 44 42 46 36 42 33 33 2D 45 32 33 46 // ..$CDBF6B33-E23F ...
| | | .custom /*0C000012:0A000002*/ instance void [mscorlib/*23000001*/]System.Runtime.InteropServices.TypeLibTypeAttribute/*01000003*/::.ctor(int16) /* 0A000002 */ = ( 01 00 02 00 00 00 ) ...
| | |___[MET] method .ctor : void()
| | |___[MET] method equals : bool(object)
| | |___[MET] method getClass : object()
| | |___[MET] method get_axb_Handle : int32()
| | |___[MET] method hashCode : int32()
| | |___[MET] method notify : void()
| | |___[MET] method notifyAll : void()
| | |___[MET] method toString : string()
| | |___[MET] method wait : object(object,object)
AccessViolationException exception
System.AccessViolationException was unhandled
Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Source=mscorlib
StackTrace:
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache)
at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache)
at System.Activator.CreateInstance(Type type, Boolean nonPublic)
at System.Activator.CreateInstance(Type type)
at WindowsApplication1.Form1.getPatientHandle_Click(Object sender, EventArgs e) in C:\Documents and Settings\Elie A. Cohen.USINC022\my documents\visual studio 2010\Projects\Repo API Example\Repo API Example\Repo API Example.vb:line 13
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(ApplicationContext context)
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
at WindowsApplication1.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:

In case you haven't figured it out already... Or if anyone else is curious... Or for myself when I get old and forgetful...
h2. Object Creation
For starters, when you create an ActiveX object from within VB, use:
Set myObject = CreateObject("JavaObject.Bean")When I refer to JavaObject.Bean, I'm meaning the full object name + ".Bean". So, in your case, you should use:
Set myObject = CreateObject("xxx.axb.Bean")h2. Location
The .dll file must be located in the JRE that is used at the time of calling. Meaning, the .dll file must be placed under <jre_home>\axbridge\bin and registered there.
In your case:
DLL:
C:\Program Files\Java\jre6\axbridge\bin
Jar:
C:\Program Files\Java\jre6\axbridge\libh4. A Note:
The only supported JRE is a 32bit version as far as I know with regards to the ActiveX bridge. Just like the packager.exe can only be found in the 32bit JDK.
h2. Methods
h3. Object Types
ActiveX Bridge does not support passing literals or arrays. However, it does support passing java's primitive data types as Objects.
Simply meaning:
h4. Invalid:
public int get_axb_Handle() {
     int Address = 12345678;
     return Address;
}h4. Valid:
public Integer get_axb_Handle() {
     int Address = 12345678;
     return Address;
}On a normal circumstance, there's little difference between the two methods. However, in the second example, the JVM does a typecast from a literal data type to a object data type, resulting in a valid object to pass through to Visual Basic. Now, obviously there are multiple ways to do a proper change, new Integer(int) for example. It doesn't matter to me. At the end of the day, you have to pass an object.
As a side note, the same idea applies when receiving data from Visual Basic.
h4. Invalid:
public void set_axb_Handle(int newHandle) {
     int Address = newHandle;
}h4. Valid:
public void set_axb_Handle(Integer newHandle) {
     int Address =newHandle;

Possible thread issues when calling java from C++/Delphi/C#

Hi,
We have a java API for one of our applications. This API has wrapper API's in C++, Delphi and C#. There are two main top level classes in te API - Client and Receiver. Both haave a receive() method.
We used to ship JRE1.3 with the API installation - this was needed to suport the user applications. Recently we haev moved to java 1.4 as the least suported version.
We have two ways of using the java API in our wrapper API's.
Method one, we instantiate the client, and call client.receive(). There are no threads etc involved here. This is working fine.
In the second method, we set a callback on the client, which starts a thread (in C++/Delphi or C#) which calls receiver.receive() and tries to get the message. This is failing.
It fails at a line which simply says "DocumentBuilderFactory.newInstance()".
This call has already been made when connecting the client and it is successful because we can see the client connected.
Whether we do client.receive() or receiver.receive() in a thread, the code passes through this line.But is throwing the exception only when we come to it through a thread.
Any ideas on what I need to watch out for when calling methods on a JVM from a thread in C++/Delphi or C#?
Thanks
Hari
PS: I know we are using some really old versions, but thats needed and out of my control.

Hi,
I managed to solve this - finally!
This is what was the cause in our case - should apply to all situations though.
We had the Xerces classes packaged in a custom jar file along with other XML stuff we have. And this mega-jar was on the class path.
We were running everything on Java 1.3 and it worked fine.
But Java 1.4 wrecked all havoc.
So here is what I did:
1. I tried explicitly doing Class.forName() with the name of the Xerces class that was not found. I did this at the same point in the code where the exception was being thrown.
2. The class was successfully loaded indicating that it was on the class path somewhere.
3. Java 1.4 made some changes in terms of class loaders - so suspecting that, I tried printing out the System and the Context class loaders at the point where the exception was being thrown - the system class loader was a valid object, but context class loader was null
4. We have another point in the code base where the exact same lines were used, and these are getting successfully executed even in the multi threaded situation - this is the start up sequence.
5. I printed the two class loaders at this point - they are both valid objects, no nulls.
With this, I narrowed down the scope and was convinced that the class loaders are the cause.
A search on Google and after looking the the source code for Xerces, we realized that the Xerces API uses the Context Class Loader to resolve and load the DocumentFactoryImpl class - this change is from Java 1.4 onwards.
In our case, the JNI AttachCurrentThread method called from C++/C# and Delphi was attaching the thread to the JVM, but each time the context class loader was null.
We could not find anything on how we could make the method to put a non null context classloader.
So, we changed all our JNI interfaces to do the following
//attach the current thred
jvm->AttachCurrentThread(...)
//now get the system class loader and set it as the context class loader on the current thread
//get things from the Thread class
jclass thread = get the thread class
jmethod currentThread = get the static method currentThread()
jobject thread_object = get the current thread object into this
jmethod setContextClassLoader = get the setContextClassLoader() method on the thread
//get the SystemClassLoader
jclass clsLoader = get the class for ClassLoader
jmethodid getSysClsLoader = get the method ID for the getSystemClassLoader() method
jobect sysClsLoader = get the system class loader by calling the above method
//set the context class loader on the thread by calling set context class loader with the sys class loader as the argumentUnfortunately I don't have the code with me right now,otherwise would have shared the same.

ResourceBundle throws MissingResourceException when calling Java from C

All,
Our code calls Java from C application.
The C code create JVM using JNI_CreateJavaVM. Due to internal design issues we don't
create the JVM with a "-classpath" option.
After creating the JVM, we create a ClassLoader (URLClassLoader), with a URL list as it's classpath.
The last step in the C code is to load a Java class using the C reference to URLClassLoader.loadClass
(I will refer to this class as classA), and than call one of it's static methods.
Please notice that classA is not instantiated, we call a static method.
At this point we are moving to the Java code...
In the Java static method we call ResourceBundle.getBundle("resources.messages"),
the result is ResourceBundle throws MissingResourceException.
- The JAR hosting "resources/messeges.properties" (refer as jarA) is include in the
ClassLoader URL paths we used for loading the Java class.
- Using a debugger we can see that ClassLoader.getSystemClassLoader() don't contain
jarA in it's URL list.
- Using the debugger we see that classA.class.getClassLoader() does contain
jarA in it's URL list.
After some investigation we see that ResourceBundle.getBundle calles to ResourceBundle.getLoader:
private static ClassLoader getLoader() {
        Class[] stack = getClassContext();
        /* Magic number 2 identifies our caller's caller */
        Class c = stack[2];
        ClassLoader cl = (c == null) ? null : c.getClassLoader();
        if (cl == null) {
            cl = ClassLoader.getSystemClassLoader();
        return cl;
    } getClassContext() - native method, this can explain the why the above work fine for Windows.
I suspect the problem raised in the above code. Since I couldn't get a debug
version of rt.jar for Solaris, I need some help.
Our environment is Solaris 8, Java 1.5.
Please note that the same code works fine on WindowsXP with the same Java version!
Thanks,
Avi

I was thinking JVM should the classpath when it is invoked. But obviously it is not and we need to assign the classpath ourselves when invoking from native side. Thanks for pointing that out. For other people's benefit the following is the code piece I for initializing JVM.
char* str1;
          char* str2;
          char* classpath;
          str1 = "-Djava.class.path=";
          str2 = std::getenv("CLASSPATH");
          classpath = (char*)malloc(strlen(str1) + strlen(str2) + 1);
          strcpy(classpath, str1);
          strcat(classpath, str2);
          if (str2 == NULL)     {
               printf("CLASSPATH environment variable is not defined.");
               exit(1);
          m_VmArgs.version = JNI_VERSION_1_4;
          m_options[0].optionString= classpath;
          m_VmArgs.options = m_options;
          m_VmArgs.nOptions = 1;
          m_VmArgs.ignoreUnrecognized = JNI_TRUE;
          JNI_GetDefaultJavaVMInitArgs(&m_VmArgs);
          /* Create the Java VM */
          m_Res = JNI_CreateJavaVM(&m_Jvm, (void**)&m_Env, &m_VmArgs);
          if (m_Res < 0) {
               printf("Can't create JVM\n");
               exit(1);
thanks,
chancellor

Calling report from form. Need PDF output

I am calling a report from a form using RUN_PRODUCT. I need to display the form in PDF format. When the user clicks the button in the form to run the report, acrobat reader should open up and the report displayed there. Please help.
Thanks

Thanks for the response. The first part worked. I am able to get the output in PDF format. In the 2nd part where I want to open acrobat and display the output, I am having some trouble with the code. When I compile, it says
win_api_environment.read_registry must be declared. Is there some package I need to attach?
Also, in the After reports trigger, how do I pass vFile (I am assuming this is the PDF file name)?
Thanks
The first thing you'll want to do is pass parameters to the report IE DESTYPE, DESNAME and DESFORMAT where these could be FILE, 'c:\temp\report' and PDF.
Then, you can try this piece of code I wrote (with some help from other people at Metalink and here) sometime back. Now, I call it from forms, but in your case, you'd have to run it in the after report trigger. Since with RUN_PRODUCT you don't know when the report is finished, if you did it from the form, it wouldn't work correctly.
PROCEDURE OPEN_PDF(vFile IN VARCHAR2)
IS
vcServerApp varchar2(40);
vcServerTag varchar2(600);
vcCommand varchar2(2000);
iArgPos pls_integer;
dummy NUMBER;
BEGIN
-- 1 get the Server App for .PDF files
vcServerApp := win_api_environment.read_registry('HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES\.PDF','',true);
-- 2 get the executable
vcServerTag := 'HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES\'||
vcServerApp||'\SHELL\OPEN\COMMAND';
vcCommand:= win_api_environment.read_registry(vcServerTag,'',true);
-- 3 Sort out how to specify the Filename
iArgPos:= instr(vcCommand,'%1');
if iArgPos = 0 then --no substitution Var on the command line
vcCommand := vcCommand||' '||vFile;
else
vcCommand := substr(vcCommand,1,(iArgPos-1))||
vFile||substr(vcCommand,(iArgPos+2));
end if;
-- 4 Run using Winexec (or Host if preferred).
win_api_shell.winexec(vcCommand);
EXCEPTION
when no_data_found then
abortt('Acrobat Reader was not found! Please consult with your help desk to install it and try again.','N');
END;
Chad
I am calling a report from a form using RUN_PRODUCT. I need to display the form in PDF format. When the user clicks the button in the form to run the report, acrobat reader should open up and the report displayed there. Please help.
Thanks

Contact name not showing in call/sms log even when I call/sms from my address book.

Two things have changed on my phone recently.
1. I ran the latest update 4.3.2
2. My phone was not showing all the contacts in my address book that is in my Mobile Me account. Mobile me had 166 contacts. The iPhone 4 had 136. I I unchecked the syncing of my contacts on my phone. This removed all the contacts from my phone. Then I check the syncing options again. All 166 appeared on the phone.
I'm not sure which of the two caused the issue but now anytime someone who calls their name does not appear on the display or log, just their number. I can even call people from my address book and the display shows that I am calling them with their name and photo on display. However, in the call log the name does not show just their number. This applies for text messages. I send a message directly from within the contact card in the address book and in my text log it shows only the number and not the name.
I've turned the phone off and on a couple of times.
I would appreciate any advice.
Cheers

Thanks iraghib,
In the end I reset my phone to factory settings. I created a back up of my address book and ical. Reset the phone and did a sync again. This fixed it all. I didn't need to use the backups but is was nice to know they were there. I felt entering the various passwords for all my installed apps was a much better deal than adding the international area code to the 166 contacts I have in my address book.
Good luck. And thanks for the post.

Calling JVM from C++

Similar Messages

Maybe you are looking for