JNI jstring 和char* 的相互转换

最新推荐文章于 2022-07-12 17:48:06 发布

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本文介绍如何在JNI中实现jstring和char*之间的相互转换。通过两个示例函数详细展示了从jstring到char*以及从char*到jstring的具体实现过程。

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JNI jstring 和char* 的相互转换

/+++++++++++++++++++++++++

//jstring to char*
//NOTICE: you need free return value,like free(ch)
char* jstringToChar(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);
env->DeleteLocalRef( 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 jstring
//NOTICE: you need free return value,like  (*env)->DeleteLocalRef( env, myObj );
jstring charToJstring(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");
jstring result= (jstring) env->NewObject(strClass, ctorID, bytes, encoding);
(env)->DeleteLocalRef(bytes);
env->DeleteLocalRef( encoding);
return result;
}
//+++++++++++++++++++++++++