Question

我有一个由Jet excelsior生成的.dll，我试图从他们生成的调用dll中提取类。我正在关注最初在c中完成的示例脚本。尽管经过数小时的研究和排除故障，我仍然无法开始使用LoadLibrary调用工作。我正在运行visual studio 2017社区做一个空白的c ++项目。这是我的电话和我能得到的一点点调试信息。任何解决方案或调试建议都是受欢迎的，因为我变得绝望，也欢迎任何关于我的c ++使用的提示，因为我仍然是一个新手：

1. HINSTANCE test = LoadLibrary(L"C:\\Full Path\\myDll.dll");
2. //Code exits before reaching this point.
3. int er = (int)GetLastError();

是的，我已经尝试将我的dll移动到我的项目目录并只调用文件名。不幸的是我无法看到getlasterror返回的内容，因为代码崩溃了。调试时，在第1行执行之前。其扩展信息是：
Name: test Value: 0xcccccccc{unused=???} unused <Unable to read memory>
我认为这是无关紧要的，因为它实际上没有被执行过？这是完整的代码，如果碰巧是相关的（它在底部失败在main（）的开头：

#include "stdafx.h"
#include <string>
#include <windows.h>
#include <iostream>
#include <C:\Program Files (x86)\Java\jdk1.8.0_131\include\jni.h>

HINSTANCE loadDll(LPCWSTR name)
{
    HINSTANCE hDll = LoadLibrary(name);
    int thing = (int)GetLastError();
    if (!hDll) {
        thing = (int)GetLastError();
        printf("Unable to load %s\n", name);
        exit(1);
    }

    printf("%s loaded\n", name);

    return hDll;
}

typedef jint(JNICALL * JNI_GetDefaultJavaVMInitArgs_func) (void *args);
typedef jint(JNICALL * JNI_CreateJavaVM_func) (JavaVM **pvm, void **penv, void *args);

/*
* Initialize JET run-time.
*/
void initJavaRT(HINSTANCE myDllHandle, JavaVM** pjvm, JNIEnv** penv)
{
    JavaVMInitArgs args;
    JNI_GetDefaultJavaVMInitArgs_func JNI_Init_Args = (jint(JNICALL *) (void *args)) GetProcAddress(myDllHandle, "JNI_GetDefaultJavaVMInitArgs");
    JNI_CreateJavaVM_func JNI_Create_VM = (jint(JNICALL *) (JavaVM **pvm, void **penv, void *args)) GetProcAddress(myDllHandle, "JNI_CreateJavaVM");

    if (!JNI_Init_Args) {
        std::cerr << "!JNI_Init_Args\n";
        printf("%s doesn't contain public JNI_GetDefaultJavaVMInitArgs\n", dllName);
        exit(1);
    }

    if (!JNI_Create_VM) {
        printf("%s doesn't contain public JNI_CreateJavaVM\n", dllName);
        exit(1);
    }

    memset(&args, 0, sizeof(args));

    /*args.version = JNI_VERSION_1_2;
    if (JNI_GetDefaultJavaVMInitArgs_func(&args) != JNI_OK) {
        printf("JNI_GetDefaultJavaVMInitArgs() failed with result %d\n", JNI_GetDefaultJavaVMInitArgs_func(&args));
        exit(1);
    }*/

    /*
    * NOTE: no JVM is actually created
    * this call to JNI_CreateJavaVM is intended for JET RT initialization
    */
    /*if (JNI_CreateJavaVM_func(pjvm, (void **)penv, &args) != JNI_OK) {
        printf("JNI_CreateJavaVM() failed with result %d\n", JNI_CreateJavaVM_func(pjvm, (void **)penv, &args));
        exit(1);
    }*/

    printf("JET RT initialized\n");
    fflush(stdout);
}


/*
* Look for class.
*/
jclass lookForClass(JNIEnv* env, char* name)
{
    jclass clazz = env->FindClass(name);

    if (!clazz) {
        printf("Unable to find class %s\n", name);
        exit(1);
    }

    printf("Class %s found\n", name);
    fflush(stdout);

    return clazz;
}


/*
* Create an object and invoke the "ifoo" instance method
*/
void invokeInstanceMethod(JNIEnv* env, jclass myClassInDll)
{
    jmethodID MID_init, MID_ifoo;
    jobject obj;

    MID_init = env->GetMethodID(myClassInDll, "<init>", "()V");
    if (!MID_init) {
        printf("Error: MyClassInDll.<init>() not found\n");
        return;
    }

    obj = env->NewObject(myClassInDll, MID_init);
    if (!obj) {
        printf("Error: failed to allocate an object\n");
        return;
    }

    MID_ifoo = env->GetMethodID(myClassInDll, "ifoo", "()V");

    if (!MID_ifoo) {
        printf("Error: MyClassInDll.ifoo() not found\n");
        return;
    }

    env->CallVoidMethod(obj, MID_ifoo);
}



/*
* Invoke the "foo" static method
*/
void invokeStaticMethod(JNIEnv* env, jclass myClassInDll)
{
    jmethodID MID_foo;

    MID_foo = env->GetStaticMethodID(myClassInDll, "parse", "()V");
    if (!MID_foo) {
        printf("\nError: MyClassInDll.foo() not found\n");
        return;
    }

    env->CallStaticVoidMethod(myClassInDll, MID_foo);
}


void finalizeJavaRT(JavaVM* jvm)
{
    jvm->DestroyJavaVM();
}


int main()
{
    //Actually just trouble shooting code, not used in full program
    HINSTANCE test = LoadLibrary(L"C:\\Full Path\\stgNativeProject.dll");
    int er = (int)GetLastError();

    //Actual program code
    HINSTANCE myDllHandle;
    JNIEnv *env;
    JavaVM *jvm;
    jclass  myClassInDll;

    /*
    * First of all, load required component.
    * By the time of JET initialization, all components should be loaded.
    */
    std::cerr << dllName << "\n";
    myDllHandle = loadDll(dllName);

    /*
    * Initialize JET run-time.
    * The handle of loaded component is used to retrieve Invocation API.
    */
    initJavaRT(myDllHandle, &jvm, &env);

    /*
    * Look for class.
    */
    myClassInDll = lookForClass(env, "MyClassInDll");

    /*
    * Create an object and invoke instance method.
    */
    invokeInstanceMethod(env, myClassInDll);

    /*
    * Invoke static method.
    */
    invokeStaticMethod(env, myClassInDll);

    /*
    * Finalize JET run-time.
    */
    finalizeJavaRT(jvm);

    return 0;
}

Answer 1

我的问题的解决方案相对简单。我正在测试一个名为Jet Excelsior的实用程序来预编译我的java代码以供本机使用。该实用程序创建一个.dll，用于c ++或c项目。我遇到的问题是，调用dll需要与Jet Pack一起打包以及Jet运行时。检查其上的文档here。如果您已下载Jet，那么Jet示例调用dlls / cmain将对您最有帮助。

c ++ LoadLibrary（）导致程序退出

1 个答案: