Java

1. Choose the correct forum for your message. Posting a VB.NET question in the C++ forum will end in tears.
   
   
2. Be specific! Don't ask "can someone send me the code to create an application that does 'X'. Pinpoint exactly what it is you need help with.
   
   
3. Keep the subject line brief, but descriptive. eg "File Serialization problem"
   
   
4. Keep the question as brief as possible. If you have to include code, include the smallest snippet of code you can.
   
   
5. Be careful when including code that you haven't made a typo. Typing mistakes can become the focal point instead of the actual question you asked.
   
   
6. Do not remove or empty a message if others have replied. Keep the thread intact and available for others to search and read. If your problem was answered then edit your message and add "[Solved]" to the subject line of the original post, and cast an approval vote to the one or several answers that really helped you.
   
   
7. If you are posting source code with your question, place it inside <pre></pre> tags. We advise you also check the "Encode HTML tags when pasting" checkbox before pasting anything inside the PRE block, and make sure "Ignore HTML tags in this message" check box is unchecked.
   
   
8. Be courteous and DON'T SHOUT. Everyone here helps because they enjoy helping others, not because it's their job.
   
   
9. Please do not post links to your question in one forum from another, unrelated forum (such as the lounge). It will be deleted.
   
   
10. Do not be abusive, offensive, inappropriate or harass anyone on the boards. Doing so will get you kicked off and banned. Play nice.
    
    
11. If you have a school or university assignment, assume that your teacher or lecturer is also reading these forums.
    
    
12. No advertising or soliciting.
    
    
13. We reserve the right to move your posts to a more appropriate forum or to delete anything deemed inappropriate or illegal.

1. Read the question carefully
   
   
2. Understand that English isn't everyone's first language so be lenient of bad spelling and grammar
   
   
3. If a question is poorly phrased then either ask for clarification, ignore it, or mark it down. Insults are not welcome
   
   
4. If the question is inappropriate then click the 'vote to remove message' button
   

/*
 ******************************************************************************
 *
 *    Name     : cpptojava.cpp
 *
 *    Function : Basic Console application to call a Java class.
 *
 *    Created  : 09 Jun 2022
 *
 ******************************************************************************
 */

#include <Windows.h>
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <filesystem> // requires -std:c++17

#include "jni.h"

//
// Find the path to the jvm.dll given the base path to the Java runtime (or JDK if installed)
//
HMODULE LoadDll(
    const char* jrePath
)
{
    const char* pszjvmname = "bin\\server\\jvm.dll";   // Java VM name
    HMODULE hJVMDLL = 0;

    std::filesystem::path jvmpath(jrePath);
    jvmpath /= pszjvmname;
    if (!std::filesystem::exists(jvmpath))
    {
        std::cerr << "JVM library " << jvmpath << " not found." << std::endl;
        // throw an exception 
    }

    // load the Java VM DLL into our address space
    // NB filesystem::path is Unicode
    hJVMDLL = LoadLibraryW(reinterpret_cast<PCWSTR>(jvmpath.c_str()));
    if (hJVMDLL != NULL)
    {
        std::clog << "jvm.dll loaded from: " << jvmpath << std::endl;
    }
    return hJVMDLL; // a Windows HANDLE to the DLL
}


//
// A function to load the Java VM and initialise the JNI interface
// There are a number of diagnostic messages to show progress
//
JNIEnv* AttachJVM(
    const char* jrePath,
    JavaVM* jvm,
    std::string strcwd
)
{
    HMODULE     hJVMDLL = LoadDll(jrePath);
    if (hJVMDLL == 0)
    {
        return nullptr;
    }
    typedef jint(JNICALL* fpCJV)(JavaVM**, void**, void*);
    fpCJV JNI_CreateJavaVM = (fpCJV)::GetProcAddress(hJVMDLL, "JNI_CreateJavaVM");

    // tell the JVM where to find the class
    JavaVMOption    options[2];
    std::stringstream ssoptions;
    ssoptions << "-Djava.class.path=";
    ssoptions << strcwd;
    std::string stropts = ssoptions.str();
    options[0].optionString = const_cast<char*>(stropts.c_str());
    options[1].optionString = const_cast<char*>("-verbose:jni");   // print JNI-related messages

    JavaVMInitArgs  vm_args; // JDK/JRE 6 VM initialization arguments
    vm_args.version = JNI_VERSION_1_8;
    vm_args.nOptions = 1; // change to 2 for verbose output
    vm_args.ignoreUnrecognized = false;
    vm_args.options = options;
    for (int i = 0; i < vm_args.nOptions; ++i)
    {
        std::clog << "Options[" << i << "]: " << options[i].optionString << std::endl;
    }
    JNIEnv* env;            // pointer to native method interface
    jint res = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);
    if (res != 0)
    {
        std::cerr << "C++: JNI_CreateJavaVM returned: " << res << std::endl;
    }
    jint version = env->GetVersion();
    std::clog << "JVM Version: " << (version >> 16) << "." << (version & 0xffff) << std::endl;

    return env; // the pointer to the jvm dll
}


void CallClass(
    JNIEnv* jniEnv,
    const char* pszClassname,
    const char* pszMethodname,
    const char* pszSignature
)
{
    jclass jvmclass = jniEnv->FindClass(pszClassname);
    if (jvmclass != NULL)
    {
        std::cout << "C++: Found the class: " << pszClassname << std::endl;
        jmethodID jmid = jniEnv->GetStaticMethodID(jvmclass, pszMethodname, pszSignature);
        if (jmid != NULL)
        {
            std::cout << "C++: Found the method: " << pszMethodname << std::endl;
            jniEnv->CallStaticVoidMethod(jvmclass, jmid, NULL);
            std::cout << "C++: env->CallStaticVoidMethod complete" << std::endl;
        }
        else
        {
            std::cerr << "C++: Failed to find the method: " << pszMethodname << std::endl;
        }
    }
    else
    {
        std::cerr << "C++: Failed to find the class: " << pszClassname << std::endl;
    }
}


int main(
    int argc,
    const char** argv
)
{
    const char* jreDir = nullptr;

    // suppress debug messages
    std::clog.setstate(std::ios::badbit);
    for (argv++; argc > 1; ++argv, --argc)
    {
        if (*argv[0] == '-')
        {
            // handle any execution options ...
            if (strstr(*argv, "-d"))
                std::clog.clear();
        }
        else
        {
            jreDir = *argv;
        }
    }
    if (jreDir == nullptr)
    {
        std::cerr << "No root path provided for JVM." << std::endl;
        return 1;
    }
    JNIEnv* jniEnv = NULL;
    std::filesystem::path cwd = std::filesystem::current_path();
    JavaVM jvm;
    jniEnv = AttachJVM(jreDir, &jvm, cwd.string());
    if (jniEnv == NULL)
    {
        std::cerr << "C++: Failed to get Java environment" << std::endl;
        return 1;
    }
        CallClass(jniEnv, "CppToJava", "main", "([Ljava/lang/String;)V");

    // clean up
    jint jvmres = jvm.DestroyJavaVM(); // never returns ???
    std::clog << "C++: DestroyJavaVM and terminate: " << jvmres << std::endl;

}

#include <jni.h>
#include <string>
#include <iostream>
#include <chrono>
#include <thread>

JavaVM* jvm = nullptr;

std::string createVM(std::string location) {
	//Here what I need to add to load the dll from location + ThirdParty\Eclipse Adoptium\jre-17.0.7.7-hotspot\bin\server
	location.insert(0, "-Djava.class.path=");
	location.append("Data\\Java");
	JavaVMInitArgs vm_args;
	JavaVMOption* options = new JavaVMOption[1];
	options[0].optionString = &location[0];
	vm_args.version = JNI_VERSION_10;
	vm_args.nOptions = 1;
	vm_args.options = options;
	vm_args.ignoreUnrecognized = false;
	JNIEnv* env = nullptr;
	jint rc = JNI_OK;
	if (jvm == nullptr) {
		rc = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);
	}
	else {
		rc = jvm->AttachCurrentThread((void**)&env, NULL);
	}
	delete[] options;
	if (rc != JNI_OK) {
		if (rc == JNI_EVERSION)
			return "JNI_EVERSION";
		else if (rc == JNI_ENOMEM)
			return "JNI_ENOMEM";
		else if (rc == JNI_EINVAL)
			return "JNI_EINVAL";
		else if (rc == JNI_EEXIST)
			return "JNI_EEXIST";
		else
			return "JNI_FATALERROR";
	}
	return "JNI_CREATED";
}

std::string createIdentification() {
	JNIEnv* env;
	jvm->AttachCurrentThread((void**)&env, NULL);
	jclass jClass = env->FindClass("JavaMethods");

	if (jClass == nullptr) {
		return "ClassNotFound cI";
	}
	else {
		jmethodID methodID = env->GetStaticMethodID(jClass, "createIdentification", "()Ljava/lang/String;");
		if (methodID == nullptr) {
			return "MethodNotFound cI";
		}
		else {
			jboolean isCopy;
			jstring jResult = (jstring)env->CallStaticObjectMethod(jClass, methodID);
			const char* string = env->GetStringUTFChars(jResult, &isCopy);
			std::string result = string;
			env->ReleaseStringUTFChars(jResult, string);

			return result;
		}
	}
}

int main() {
	//As an example I wrote a possible location
	std::cout << createVM("D:\\Program Files\\MyApp\\").c_str() << std::endl;
	std::cout << createIdentification().c_str();

	std::this_thread::sleep_for(std::chrono::milliseconds(2000));
	return 0;
}

System.out.println("Starting client");
Socket socket = new Socket("localhost", port);
System.out.println("Client sending data");
ObjectOutputStream dataOut = new ObjectOutputStream(socket.getOutputStream());
BufferedInputStream is = new BufferedInputStream(new FileInputStream(inFile));
byte[] buffer = new byte[8192];
int sizeRead = 0;
while ((sizeRead = is.read(buffer, 0, 8192)) >= 0) {
    printByte(buffer, "in"); //Function that writes to a file as strings the byte[], and after 8192 you can see it is the first byte[] each time, also it writes at the end of file
    dataOut.writeObject(true);
    dataOut.writeObject(buffer);
    dataOut.writeObject(sizeRead);
    dataOut.flush();
}
is.close();
System.out.println("Done sending file");
dataOut.writeObject(false);
socket.close();
System.out.println("Client closed");

System.out.println("Starting server");
ServerSocket server = new ServerSocket(port);
System.out.println("Server waiting");
Socket socket = server.accept();
System.out.println("Client connected");
ObjectInputStream dataIn = new ObjectInputStream(socket.getInputStream());
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(outFile));
Object auxKeepReading = dataIn.readObject();
if (auxKeepReading instanceof Boolean) {
    while ((boolean) auxKeepReading) {
        Object auxBuffer = dataIn.readObject();
        if (!(auxBuffer instanceof byte[])) {
            System.out.println("Broke byte");
            break;
        }
        Object auxSize = dataIn.readObject();
        if (!(auxSize instanceof Integer)) {
            System.out.println("Broke int");
            break;
        }
        printByte((byte[]) auxBuffer, "out"); //Same as on client but different file, it writes at the end of file each time
        bos.write((byte[]) auxBuffer, 0, (int) auxSize);

        auxKeepReading = dataIn.readObject();
        if (!(auxKeepReading instanceof Boolean)) {
            System.out.println("Broke boolean");
            break;
        }
    }
} else {
    System.out.println("Broke boolean");
}
bos.close();
socket.close();
server.close();
System.out.println("Server stopped");