vc++调用jar包

一、编写jar包

    定义如下接口

static public String GetVersion()

public void SetLucenePath(String LucenePath)

// 添加索引

public void addIndex(Info info) throws IOException

// 关键字查询

public List<Info> search(String q, int pageSize, int pageIndex) throws Exception

// 删除索引索引

public void dellAllIndex() throws Exception

二、c++调用jar包

    加载jvm必须使用loadlibrary方式，否则程序必须运行在jvm.dll同级目录下。

   c++文本需要转换为utf8传输给java，接收的java文本需要转换成gb2312才能正常显示。

三、示例

bool CLuceneJava::Init()

{

JavaVMInitArgs vmArgs;

vmArgs.version = JNI_VERSION_1_8;

const int OPTION_COUNT = 3;

vmArgs.nOptions = OPTION_COUNT;

JavaVMOption options[OPTION_COUNT] = { 0 };

// classpath 指定为我们要调用的 jar 包路径

options[0].optionString = "-Djava.class.path=d://soskp.jar";

options[1].optionString = "-Xmx1024m";  // 最大堆大小

options[2].optionString = "-verbose:NONE"; //用于跟踪运行时的信息

vmArgs.options = options;

vmArgs.ignoreUnrecognized = JNI_TRUE;

HMODULE hModule = LoadLibrary("D:\\Java\\jdk-17.0.14\\bin\\server\\jvm.dll");

if (hModule == NULL)

return false;

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

CreateJavaVMFuncPtr CreateJavaVM = (CreateJavaVMFuncPtr)GetProcAddress(hModule, "JNI_CreateJavaVM");

JavaVM* jvm = nullptr;

JNIEnv* env = nullptr;

try {

jint res = (*CreateJavaVM)(&jvm, (void**)&env, &vmArgs);

if (res != JNI_OK)

return false;

}

catch (exception ex) {

printf("%s\r\n", ex.what());

}

// 找到 MyLucene

jclass class_MyLucene = env->FindClass("com/soskp/MyLucene/MyLucene");

jmethodID method_c = env->GetMethodID(class_MyLucene, "<init>", "()V");

jobject obj = env->NewObject(class_MyLucene, method_c);

// SetLucenePath

jmethodID method_SetLucenePath = env->GetMethodID(class_MyLucene, "SetLucenePath", "(Ljava/lang/String;)V");

jstring _jstrPath = env->NewStringUTF("d:\\luc");

env->CallVoidMethod(obj, method_SetLucenePath, _jstrPath);

env->DeleteLocalRef(_jstrPath);

/*

// dellAllIndex

jmethodID method_dellAllIndex = env->GetMethodID(class_MyLucene, "dellAllIndex", "()V");

env->CallVoidMethod(obj, method_dellAllIndex);

// 检查是否有异常

if (env->ExceptionCheck())

{

env->ExceptionDescribe();

env->ExceptionClear();

}

*/

// GetVersion

jmethodID methodId_GetVersion = env->GetStaticMethodID(class_MyLucene, "GetVersion", "()Ljava/lang/String;");

jstring strVer = (jstring)env->CallStaticObjectMethod(class_MyLucene, methodId_GetVersion, "");

string str_Ver = jstring2string(env, strVer);

printf("%s\r\n", str_Ver.c_str());

// Info

jclass class_Info = env->FindClass("com/soskp/MyLucene/entity/Info");

jmethodID method_Infoc = env->GetMethodID(class_Info, "<init>", "()V");

jobject objInfo = env->NewObject(class_Info, method_Infoc);

// Info setId Integer

jint id = 11;

jclass intClass = env->FindClass("java/lang/Integer");

jmethodID intConstructor = env->GetMethodID(intClass, "<init>", "(I)V");

jobject intObj = env->NewObject(intClass, intConstructor, id);

// Info setId

jmethodID method_setId = env->GetMethodID(class_Info, "setInfoId", "(Ljava/lang/Integer;)V");

if(method_setId!=NULL)

printf("Info method_setId\n");

env->CallVoidMethod(objInfo, method_setId, intObj);

// Info setTitle

jmethodID method_setTitle = env->GetMethodID(class_Info, "setTitle", "(Ljava/lang/String;)V");

string tt1 = ConvertGB2312ToUTF8(t1);

jstring _jsetTitle = env->NewStringUTF(tt1.c_str());

env->CallVoidMethod(objInfo, method_setTitle, _jsetTitle);

env->DeleteLocalRef(_jsetTitle);

// Info setContent

jmethodID method_setContent = env->GetMethodID(class_Info, "setContent", "(Ljava/lang/String;)V");

string tt2 = ConvertGB2312ToUTF8(t2);

jstring _jsetContent = env->NewStringUTF(tt2.c_str());

env->CallVoidMethod(objInfo, method_setContent, _jsetContent);

env->DeleteLocalRef(_jsetContent);

// addIndex

jmethodID method_addIndex = env->GetMethodID(class_MyLucene, "addIndex", "(Lcom/soskp/MyLucene/entity/Info;)V");

env->CallVoidMethod(obj, method_addIndex, objInfo);

// 检查是否有异常

if (env->ExceptionCheck())

{

env->ExceptionDescribe();

env->ExceptionClear();

}

printf("addIndex\n");

// search

jmethodID method_search = env->GetMethodID(class_MyLucene, "search", "(Ljava/lang/String;II)Ljava/util/List;");

string keyword = ConvertGB2312ToUTF8("驱动器");

jstring jQuery = env->NewStringUTF(keyword.c_str());

jobject objSearchResult = (jobject)env->CallObjectMethod(obj, method_search, jQuery, 20, 0);

env->DeleteLocalRef(jQuery);

// 检查是否有异常

if (env->ExceptionCheck())

{

env->ExceptionDescribe();

env->ExceptionClear();

}

printf("search\n");

//5. 遍历List并打印所有Info对象

if (objSearchResult == nullptr)

return 0;

jclass listClass = env->FindClass("java/util/List");

// 获取List的size方法

jmethodID listSizeMethod = env->GetMethodID(listClass, "size", "()I");

if (listSizeMethod == nullptr) {

return nullptr;

}

int size = env->CallIntMethod(objSearchResult, listSizeMethod);

printf("search result size: %d\n", size);

// 获取List的get方法

jmethodID listGetMethod = env->GetMethodID(listClass, "get", "(I)Ljava/lang/Object;");

// 遍历每个元素

for (int i =0; i < size; i++)

{

jobject infoObj = env->CallObjectMethod(objSearchResult, listGetMethod, i);

// 获取Info类

jclass infoClass = env->FindClass("com/soskp/MyLucene/entity/Info");

// 获取Info的getTitle方法

jmethodID getTitleMethod = env->GetMethodID(infoClass, "getTitle", "()Ljava/lang/String;");

// 获取Info的getId方法

jmethodID getInfoIdMethod = env->GetMethodID(infoClass, "getInfoId", "()Ljava/lang/Integer;");

// 调用getTitle方法

jstring strTitle = (jstring)env->CallObjectMethod(infoObj, getTitleMethod);

const char* nameChars = env->GetStringUTFChars(strTitle, nullptr);

string cppName(nameChars);

env->ReleaseStringUTFChars(strTitle, nameChars);

// 调用getId方法

jobject objInfoId = env->CallObjectMethod(infoObj, getInfoIdMethod);

//5. 将返回的Integer对象转换为C++的int类型

jclass integerClass = env->FindClass("java/lang/Integer");

// 获取intValue方法的ID

jmethodID intValueMethod = env->GetMethodID(integerClass, "intValue", "()I");

// 调用intValue方法获取int值

jint id = env->CallIntMethod(objInfoId, intValueMethod);

// 打印Info对象的信息

cppName = ConvertUTF8toGB2312(cppName);

printf("Info: Name = %s, Id = %d\n",cppName.c_str(), id);

// 删除局部引用

env->DeleteLocalRef(infoObj);

env->DeleteLocalRef(strTitle);

}

// 删除局部引用

env->DeleteLocalRef(objSearchResult);

env->DeleteLocalRef(listClass);

printf("OK result\n");

// 检查是否发生了Java异常

jthrowable exception = env->ExceptionOccurred();

if (exception != NULL)

{

// 打印Java异常的堆栈跟踪信息

env->ExceptionDescribe();

// 抛出新的Java异常，类型为java.lang.RuntimeException，信息为"JNI error"

jclass runtimeExceptionClass = env->FindClass("java/lang/RuntimeException");

env->ThrowNew(runtimeExceptionClass, "JNI error");

}

jvm->DestroyJavaVM();

FreeLibrary(hModule);

return true;

}