Loading DLL from file not PATH
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You should not do this; Java uses other items in its run-time library. Any client wishing to run your application will need to install Java before they can use it. And it is quite possible that if you install the dll yourself you will be breaching Oracle's licencing conditions.
I thought that is the problem but then what is the solution for this? Having the user to install Java isn't a problem, but even if it is installed, I still need to add something in Visual Studio to know where to look for
jvm.dllas it is the case with/includeand/include/win32, or else it will give me an error with "jvm.dll not found". -
I thought that is the problem but then what is the solution for this? Having the user to install Java isn't a problem, but even if it is installed, I still need to add something in Visual Studio to know where to look for
jvm.dllas it is the case with/includeand/include/win32, or else it will give me an error with "jvm.dll not found".You have to read the documentation about what and where is to be written while installing the Java. Perhaps you will also need to check the registry to find out where Java installer stores the path you need for your application to work properly.
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I thought that is the problem but then what is the solution for this? Having the user to install Java isn't a problem, but even if it is installed, I still need to add something in Visual Studio to know where to look for
jvm.dllas it is the case with/includeand/include/win32, or else it will give me an error with "jvm.dll not found".If the customer correctly installs the Java runtime then it will set the PATH variable with the correct details. Your code should then run correctly. I have done a test on my system and that is all that is needed as far as I can tell. The /include and /include/win32 files are only required to build your application, not to run it. The customer just needs the correct C/C++ libraries installed - Latest supported Visual C++ Redistributable downloads | Microsoft Docs[^].
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I was reading this turorial on how to use Java in your C++ project, and at one step it says to add the location of
jvm.dllto PATH. Well that is fine for developing purpose, but not for a released project. So instead of that I tried the second part, to add it manually to Debug/Release folder and remove the location from PATH, but unfortunately I'm getting the following error:Error occurred during initialization of VM
Failed setting boot class path.What I'm I doing wrong, and how to fix the problem?
For C++ projects, I think in some versions of Visual Studio the 'current directory' is actually the $(SolutionDir) or maybe $(ProjectDir) when you run from the IDE. Using a search engine[^] you will find that the JVM is loaded with
LOAD_WITH_ALTERED_SEARCH_PATHHave a look here: Dynamic-Link Library Search Order - Win32 apps | Microsoft Docs[^] Scroll down to the documentation aboutLOAD_WITH_ALTERED_SEARCH_PATHThis flag means that the path containing the executable will never be checked. The 'current directory' is checked. Which I believe is $(SolutionDir) or maybe $(ProjectDir) when you launch from Visual Studio. -
I was reading this turorial on how to use Java in your C++ project, and at one step it says to add the location of
jvm.dllto PATH. Well that is fine for developing purpose, but not for a released project. So instead of that I tried the second part, to add it manually to Debug/Release folder and remove the location from PATH, but unfortunately I'm getting the following error:Error occurred during initialization of VM
Failed setting boot class path.What I'm I doing wrong, and how to fix the problem?
I wanted to try Java 1.8.0_202 to test some other stuff, but after changing in PATH the location for
jvm.dllfor this version, and also in Visual Studio the location for the folders /include,/include/win32, and /jdk1.8.0_202/lib forjvm.lib, now I'm getting that it can't find the class file. I tried the following (solution name "Article-JNI-1", project name "Example3", class file name "MyTest.class"): - Leaving the class in "\Article-JNI-1\Exemple3" folder; - Moving it to "\Article-JNI-1"; - Moving it to "\Article-JNI-1\x64\Debug"; - Changing code tooptions[0].optionString = "-Djava.class.path=D:\\";and moving the class there. In all those situations I'm getting the same thing, the error from line 58:cerr << "ERROR: class not found !";
While working with
jdk-17.0.1it was working fine when running from Visual Studio. What am I missing/doing wrong? -
I wanted to try Java 1.8.0_202 to test some other stuff, but after changing in PATH the location for
jvm.dllfor this version, and also in Visual Studio the location for the folders /include,/include/win32, and /jdk1.8.0_202/lib forjvm.lib, now I'm getting that it can't find the class file. I tried the following (solution name "Article-JNI-1", project name "Example3", class file name "MyTest.class"): - Leaving the class in "\Article-JNI-1\Exemple3" folder; - Moving it to "\Article-JNI-1"; - Moving it to "\Article-JNI-1\x64\Debug"; - Changing code tooptions[0].optionString = "-Djava.class.path=D:\\";and moving the class there. In all those situations I'm getting the same thing, the error from line 58:cerr << "ERROR: class not found !";
While working with
jdk-17.0.1it was working fine when running from Visual Studio. What am I missing/doing wrong?This is the code I use to load a class from C++:
//
// A function to start the Java VM and initialise the JNI interface
//
JNIEnv* createJVM(
JavaVM* jvm,
std::string strcwd
)
{
// tell the JVM where to find the class
JavaVMOption options{};
std::stringstream ssoptions;
ssoptions << "-Djava.class.path=";
// the class files are in the current directory.
// change this if yours are somewhere else
ssoptions << strcwd;
std::string stropts = ssoptions.str();
options.optionString = const_cast(stropts.c_str());JavaVMInitArgs vm\_args; // JDK/JRE 6 VM initialization arguments vm\_args.version = JNI\_VERSION\_1\_8; vm\_args.nOptions = 1; vm\_args.ignoreUnrecognized = false; vm\_args.options = &options; JNIEnv\* env; // pointer to native method interface // this should load the jvm.dll based on the PATH variable jint res = JNI\_CreateJavaVM(&jvm, (void\*\*)&env, &vm\_args); if (res != 0) { std::cout << "C++: JNI\_CreateJavaVM returned: " << res << std::endl; } return env;}
The caller then uses the
envpointer to access the remaining JNI functions. -
This is the code I use to load a class from C++:
//
// A function to start the Java VM and initialise the JNI interface
//
JNIEnv* createJVM(
JavaVM* jvm,
std::string strcwd
)
{
// tell the JVM where to find the class
JavaVMOption options{};
std::stringstream ssoptions;
ssoptions << "-Djava.class.path=";
// the class files are in the current directory.
// change this if yours are somewhere else
ssoptions << strcwd;
std::string stropts = ssoptions.str();
options.optionString = const_cast(stropts.c_str());JavaVMInitArgs vm\_args; // JDK/JRE 6 VM initialization arguments vm\_args.version = JNI\_VERSION\_1\_8; vm\_args.nOptions = 1; vm\_args.ignoreUnrecognized = false; vm\_args.options = &options; JNIEnv\* env; // pointer to native method interface // this should load the jvm.dll based on the PATH variable jint res = JNI\_CreateJavaVM(&jvm, (void\*\*)&env, &vm\_args); if (res != 0) { std::cout << "C++: JNI\_CreateJavaVM returned: " << res << std::endl; } return env;}
The caller then uses the
envpointer to access the remaining JNI functions.I added your function but I have the same result. And so I decided to do a little bit of testing. In Visual Studio I left the locations for
jdk1.8.0_202in properties, but I changed in PATH the location forjvm.dll. IF I'm using the PATH forjdk-17.0.1it is working fine, but as soon as I change it tojdk1.8.0_202it doesn't find the class anymore. -
I added your function but I have the same result. And so I decided to do a little bit of testing. In Visual Studio I left the locations for
jdk1.8.0_202in properties, but I changed in PATH the location forjvm.dll. IF I'm using the PATH forjdk-17.0.1it is working fine, but as soon as I change it tojdk1.8.0_202it doesn't find the class anymore. -
There should be no difference between the two. But Without access to your system it is impossible to guess what might be the problem.
I just created 2 new VM's (Windows 10 x64), in one I installed Java SE 8 with Visual Studio, and I was getting the same thing, class not found, then I installed Java SE 17 and just like on host, no problem it is running fine. Then on the second machine I installed Java from oracle ^, which the user would do, and copied the working executable (with no errors) to it (after installing needed redistributable of curse) but I'm getting "jvm.dll" not found error.
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I just created 2 new VM's (Windows 10 x64), in one I installed Java SE 8 with Visual Studio, and I was getting the same thing, class not found, then I installed Java SE 17 and just like on host, no problem it is running fine. Then on the second machine I installed Java from oracle ^, which the user would do, and copied the working executable (with no errors) to it (after installing needed redistributable of curse) but I'm getting "jvm.dll" not found error.
I just installed the 1.8 version of Java and rebuilt my project and it works fine. Have you checked that you are not trying to mix x86 and x64 code? Version 17 is x64 only, but 1.8 offers both. So if you have the x86 version installed that could be the problem.
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Yeah, to be sure there isn't a problem with the installation, I even just uninstalled everything Java related, and reinstalled them. I don't even have a folder in "Program files (x86)", and in x64 I have these only 17 and 1.8 (and what I'm working on right now it is for x64 only anyway): https://i.ibb.co/X3xcDcf/image.png[^] When I have in PATH location from 1.8: https://i.ibb.co/K0vzM4J/image.png[^] And when I have in PATH location from 17: https://i.ibb.co/d23HNTv/image.png[^] It is the project from that tutorial with unmodified files. I even did some Java socket call tests from C++ and they worked fine with 17. That is kinda the main reason I need this Java/C++ combination for, as I already have some systems made in Java that this new project (made in Unreal Engine which is C++) will relay on.
Make sure that you build the C++ part and the Java part with the same version of Java, they may not be fully compatible across different versions. Also, rather than using pictures to post simple text information, please use copy and paste and add it to your question.
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Make sure that you build the C++ part and the Java part with the same version of Java, they may not be fully compatible across different versions. Also, rather than using pictures to post simple text information, please use copy and paste and add it to your question.
Yeah that was the problem for saying that it can't find the class, I just added target and source and now it is working, but the second part is still a problem. I copied the released executable and the class file to a freshly created VM with only Java and redistributable installed and I'm getting the same error:
Example3.exe - System Error
The code execution cannot proceed because jvm.dll was not found. Reinstalling the program may fix this problem.
Off topic: They should add an image preview, because those are really useful.
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I just installed the 1.8 version of Java and rebuilt my project and it works fine. Have you checked that you are not trying to mix x86 and x64 code? Version 17 is x64 only, but 1.8 offers both. So if you have the x86 version installed that could be the problem.
Yeah, to be sure there isn't a problem with the installation, I even just uninstalled everything Java related, and reinstalled them. I don't even have a folder in "Program files (x86)", and in x64 I have these only 17 and 1.8 (and what I'm working on right now it is for x64 only anyway): https://i.ibb.co/X3xcDcf/image.png[^] When I have in PATH location from 1.8: https://i.ibb.co/K0vzM4J/image.png[^] And when I have in PATH location from 17: https://i.ibb.co/d23HNTv/image.png[^] It is the project from that tutorial with unmodified files. I even did some Java socket call tests from C++ and they worked fine with 17. That is kinda the main reason I need this Java/C++ combination for, as I already have some systems made in Java that this new project (made in Unreal Engine which is C++) will relay on.
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Yeah that was the problem for saying that it can't find the class, I just added target and source and now it is working, but the second part is still a problem. I copied the released executable and the class file to a freshly created VM with only Java and redistributable installed and I'm getting the same error:
Example3.exe - System Error
The code execution cannot proceed because jvm.dll was not found. Reinstalling the program may fix this problem.
Off topic: They should add an image preview, because those are really useful.
Valentinor wrote:
The code execution cannot proceed because jvm.dll was not found.
I think I have answered that more than once.
Valentinor wrote:
They should add an image preview
This has been rejected a number of times as it would be open to abuse by spammers.
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Valentinor wrote:
The code execution cannot proceed because jvm.dll was not found.
I think I have answered that more than once.
Valentinor wrote:
They should add an image preview
This has been rejected a number of times as it would be open to abuse by spammers.
Richard MacCutchan wrote:
If the customer correctly installs the Java runtime then it will set the PATH variable with the correct details. Your code should then run correctly. I have done a test on my system and that is all that is needed as far as I can tell.
You did said this, and I've done it, even on 2 new separate VM's, installed Java and needed redistributable and on both I get the same error.
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Richard MacCutchan wrote:
If the customer correctly installs the Java runtime then it will set the PATH variable with the correct details. Your code should then run correctly. I have done a test on my system and that is all that is needed as far as I can tell.
You did said this, and I've done it, even on 2 new separate VM's, installed Java and needed redistributable and on both I get the same error.
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So you keep saying. But I cannot see what is happening on your system. I have tried multiple tests of this issue with Java versions 1.8, 14 and 17 and cannot recreate the problem you are having.
unknown 2022 06 16 11 59 - YouTube[^] Here is a video, first run is on host where I have jdk, Visual Studio..., and second is on VM.
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unknown 2022 06 16 11 59 - YouTube[^] Here is a video, first run is on host where I have jdk, Visual Studio..., and second is on VM.
I owe you an apology. I do not have a VM to run this on so my reinstalls of Java were missing something that I had set up in the past. The jvm.dll is not in the bin directory of the JRE installation, but in a subdirectory named server. This was in my PATH variable and was not removed when I uninstalled one of the Java versions. So you need to add that location to the PATH variable manually. Sorry again for the confusion.
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I owe you an apology. I do not have a VM to run this on so my reinstalls of Java were missing something that I had set up in the past. The jvm.dll is not in the bin directory of the JRE installation, but in a subdirectory named server. This was in my PATH variable and was not removed when I uninstalled one of the Java versions. So you need to add that location to the PATH variable manually. Sorry again for the confusion.
The thing is that when Java is installed it doesn't add some kind of dynamic link in PATH to where
jvm.dllis located, well it doesn't add one at all. Yes, if I'm compiling the class with 1.8 and then on VM I can manually add in PATH the server folder, but here is a problem, the user should not go though this process of opening variables and find PATH to add it there. A solution would be that when the app is opened, it would check if Java in installed, if it is not, then the user would be prompted to download it, or I have to search and see if you can legally distributeJavaSetup8uxxx.exefile and if you can the app would automatically run the file and the user would go though the process of installing Java. After Java is installed by either way then the app will search what version is installed to know what location to add in PATH, which it would do after knowing that. At this point the app will run fine. BUT then you run into another problem, if the user updates Java then the location will change forjvm.dll, so you would have to add another variable to PATH with the new location for it, and remove the old one. Adding a variable to PATH shouldn't be a problem, as Java and other programs do it too, I'll just have to see how that is done from C++ code. If this is actually the only way to do it, then I guess I can do it this way, but having another solution that wouldn't involve adding variables to PATH would have been better. -
The thing is that when Java is installed it doesn't add some kind of dynamic link in PATH to where
jvm.dllis located, well it doesn't add one at all. Yes, if I'm compiling the class with 1.8 and then on VM I can manually add in PATH the server folder, but here is a problem, the user should not go though this process of opening variables and find PATH to add it there. A solution would be that when the app is opened, it would check if Java in installed, if it is not, then the user would be prompted to download it, or I have to search and see if you can legally distributeJavaSetup8uxxx.exefile and if you can the app would automatically run the file and the user would go though the process of installing Java. After Java is installed by either way then the app will search what version is installed to know what location to add in PATH, which it would do after knowing that. At this point the app will run fine. BUT then you run into another problem, if the user updates Java then the location will change forjvm.dll, so you would have to add another variable to PATH with the new location for it, and remove the old one. Adding a variable to PATH shouldn't be a problem, as Java and other programs do it too, I'll just have to see how that is done from C++ code. If this is actually the only way to do it, then I guess I can do it this way, but having another solution that wouldn't involve adding variables to PATH would have been better.
