java - JNI - 【 java <-> C++ String 的转换 】

jstring 和char* 之间是如何转换的

//jstring to char*char* jstringTostring(JNIEnv* env, jstring jstr){       char* rtn = NULL;       jclass clsstring = env->FindClass("java/lang/String");       jstring strencode = env->NewStringUTF("utf-8");       jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");       jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);       jsize alen = env->GetArrayLength(barr);       jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);       if (alen > 0)       {                 rtn = (char*)malloc(alen + 1);                 memcpy(rtn, ba, alen);                 rtn[alen] = 0;       }       env->ReleaseByteArrayElements(barr, ba, 0);       return rtn;}//char* to jstringjstring stoJstring(JNIEnv* env, const char* pat){       jclass strClass = env->FindClass("Ljava/lang/String;");       jmethodID ctorID = env->GetMethodID(strClass, "<init>", "([BLjava/lang/String;)V");       jbyteArray bytes = env->NewByteArray(strlen(pat));       env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);       jstring encoding = env->NewStringUTF("utf-8");       return (jstring)env->NewObject(strClass, ctorID, bytes, encoding);}//invoke functionJNIEXPORT jstring JNICALL Java_test_cs_web_SWIFTAlianceCASmfTest_strcal  (JNIEnv *env, jclass obj, jstring jstr1, jstring jstr2){    jbyteArray bytes = 0;    jthrowable exc;    char *pszResult = NULL;        char *pszSTR1 = NULL;    char *pszSTR2 = NULL;        pszSTR1 = jstringTostring(env, jstr1);    pszSTR2 = jstringTostring(env, jstr2);    int nlen = sizeof(char)*(strlen(pszSTR1)+strlen(pszSTR2));    pszResult = (char*)malloc(nlen);    strcpy(pszResult, pszSTR1);    strcat(pszResult, pszSTR2);    jstring jstrRe = stoJstring(env, pszResult);    free(pszSTR1);    free(pszSTR2);    free(pszResult);    return(jstrRe);}