JNI中 jstring与 char* 格式互转

//以下gcc能编译过，且正确，vc++下可能错误

char* jstringtochar( JNIEnv *env, jstring jstr )
{
char* rtn = NULL;
jclass clsstring = (*env)->FindClass(env,"java/lang/String");
jstring strencode = (*env)->NewStringUTF(env,"utf-8");
jmethodID mid = (*env)->GetMethodID(env,clsstring, "getBytes", "(Ljava/lang/String;)[B");
jbyteArray barr= (jbyteArray)(*env)->CallObjectMethod(env,jstr, mid, strencode);
jsize alen = (*env)->GetArrayLength(env,barr);
jbyte* ba = (*env)->GetByteArrayElements(env,barr, JNI_FALSE);
if (alen > 0)
{
rtn = (char*)malloc(alen + 1);
memcpy(rtn, ba, alen);
rtn[alen] = 0;
}
(*env)->ReleaseByteArrayElements(env,barr, ba, 0);
return rtn;
}

jstring chartojstring( JNIEnv* env, char* pat )
{
jclass strClass = (*env)->FindClass(env,"Ljava/lang/String;");
jmethodID ctorID = (*env)->GetMethodID(env,strClass, "<init>", "([BLjava/lang/String;)V");
jbyteArray bytes = (*env)->NewByteArray(env,strlen(pat));
(*env)->SetByteArrayRegion(env,bytes, 0, strlen(pat), (jbyte*)pat);
jstring encoding = (*env)->NewStringUTF(env,"utf-8");
return (jstring)(*env)->NewObject(env,strClass, ctorID, bytes, encoding);
}