JNI C language jstring and char * conversion

char * turn jstring

 

jstring charToJstring(JNIEnv *env, const char *pat) {
    jclass strClass = (*env)->FindClass(env, "java/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);
}

jstring turn char *

 

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;
}