ArangoDB java driver on executing AQL sometimes return NULL and other times the correct result

ArangoDB java driver on executing AQL sometimes return NULL and other times the correct result

By : 문찬용
Date : November 20 2020, 11:01 PM
To fix the issue you can do As AntJavaDev said, you access bindVar more than once the same time. When one thread modify bindVar and another tried to build the AQL call at the same time by reading bindVar. This leads to the ConcurrentModificationException.
The NullPointerException results from an AQL call with no result. e.g. when you clear bindVar and directly after that, execute the AQL in another thread with no content in bindVar.
code :

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How to return the correct datatype with MongoDB Java Driver

How to return the correct datatype with MongoDB Java Driver

By : Patience
Date : March 29 2020, 07:55 AM
this will help When inserting using mongoshell, you need to explicitly say NumberInt(0) or NumberLong(0) if you want to have integer values. Otherwise, MongoDB will use floating point values.
When you do a find() in mongodb shell, it will also return NumberInt(0) or NumberLong(0) if it is an integer.
Maven is not detecting ArangoDB 2.8.6 java driver

Maven is not detecting ArangoDB 2.8.6 java driver

By : Hillgo
Date : March 29 2020, 07:55 AM
this will help You have mixed up the versions. The latest available version of the driver is 2.7.4 (or 2.7.5-SNAPSHOT if you prefer snapshots), even in the GitHub link you have provided.
However, the ArangoDB version supported includes ArangoDB 2.8.x so even with the 2.7.4 driver you should be able to use ArangoDB 2.8.6, which I suspect is what you want.
code :
ArangoDB Java Driver Caching Not Working

ArangoDB Java Driver Caching Not Working

By : Libdeo Mikael Peliño
Date : March 29 2020, 07:55 AM
it fixes the issue We tested Caching with the following Testcase and saw a performance improvement. Can you post an example of your query?
code :
public class ArangoDriverCacheTest {

    private static final String COLLECTION_NAME = "unitTestCollection";
    private static final String DATABASE_NAME = "unitTestDatabase";
    private static ArangoConfigure configure;
    private static ArangoDriver driver;

    public static void setup() throws ArangoException {

        configure = new ArangoConfigure();
        driver = new ArangoDriver(configure);

        // // create test database
        try {
        } catch (final ArangoException e) {

        // create test collection
        try {
        } catch (final ArangoException e) {

        // create some test data
        for (int i = 0; i < 1000000; i++) {
            final TestEntity value = new TestEntity("user_" + (i % 10), "desc" + (i % 10), i);
            driver.createDocument(COLLECTION_NAME, value);


    public static void shutdown() {
        try {
        } catch (final ArangoException e) {

    private AqlQueryOptions createAqlQueryOptions(
        final Boolean count,
        final Integer batchSize,
        final Boolean fullCount,
        final Boolean cache) {
        return new AqlQueryOptions().setCount(count).setBatchSize(batchSize).setFullCount(fullCount).setCache(cache);

    public void test_withoutCache() throws ArangoException {
        // set cache mode off
        final QueryCachePropertiesEntity properties = new QueryCachePropertiesEntity();


    public void test_withCache() throws ArangoException {
        // set cache mode on
        final QueryCachePropertiesEntity properties = new QueryCachePropertiesEntity();

        // set caching to true for the query

    private void exceuteQuery(final boolean cache) throws ArangoException {

        final AqlQueryOptions aqlQueryOptions = createAqlQueryOptions(true, 1000, null, cache);
        final String query = "FOR t IN " + COLLECTION_NAME + " FILTER t.age >= @age SORT t.age RETURN t";
        final Map<String, Object> bindVars = new MapBuilder().put("age", 90).get();

        DocumentCursor<TestEntity> rs = driver.executeDocumentQuery(query, bindVars, aqlQueryOptions, TestEntity.class);
        // first time, the query isn't cached
        Assert.assertEquals(false, rs.isCached());

        final long start = System.currentTimeMillis();

        // query the cached value
        rs = driver.executeDocumentQuery(query, bindVars, aqlQueryOptions, TestEntity.class);
        Assert.assertEquals(cache, rs.isCached());

        // load all results

        final long time = System.currentTimeMillis() - start;
        System.out.println(String.format("time with cache=%s: %sms", cache, time));

    private static class TestEntity {
        private final String user;
        private final String desc;
        private final Integer age;

        public TestEntity(final String user, final String desc, final Integer age) {
            this.user = user;
            this.desc = desc;
            this.age = age;
ArangoDB - Executing AQL using java driver 4.0.0 using filter returns null

ArangoDB - Executing AQL using java driver 4.0.0 using filter returns null

By : Mona
Date : March 29 2020, 07:55 AM
seems to work fine This is a bug in the DB in version 3.1.RC2. It is fixed in final version 3.1, which we release at the moment. It should be available in the next 1-2 days. With that version you need the driver in version 4.1.0, because we changed the velocystream protocol in the DB version 3.1, to remove the need of an extra velocystream endpoint. Driver version 4.1.0 only works with the final release and not with the RCs.
Single event live data emits null values multiple times will giving the correct result

Single event live data emits null values multiple times will giving the correct result

By : BrownPanick
Date : March 29 2020, 07:55 AM
this will help Each layer has some mistakes with varying importance. Let's go over them one by one.
[1] Fragment attaching observer inside of a click listener
code :
// Create this new function
fun getLoginStatus(): LiveData<SingleLiveEvent<Resource<UserSession>>> {
    return loginMutableData

// Notice this function does not return anything.
fun generalLogin(email: String, encryptedPassword: String) {

    val login = Global.network.login(email, encryptedPassword)

    login.enqueue(object : Callback<LoginResponse> {

        override fun onResponse(call: Call<LoginResponse>, response: Response<LoginResponse>) {

        override fun onFailure(call: Call<LoginResponse>, t: Throwable) {

val userSessionLiveData: LiveData<SingleLiveEvent<Resource<UserSession>>>
// val userSessionLiveData: LiveData<Resource<UserSession>>

init {

    userSessionLiveData = loginRepository.getLoginStatus()

    // Use below if some mapping needs to be done
    // userSessionLiveData = Transformations.map(loginRepository.getLoginStatus()) {
    //     return it?.contentIfNotHandled?
    // }

fun generalLogin(email: String, password: String) {
    val encryptedPassword = MCryptHelper.bytesToHex(MCryptHelper().encrypt(password))
    loginRepository.generalLogin(email, encryptedPassword)
void onCreateView(...): View {
    viewModel.userSEssionLiveData.observe(viewLifecycleOwner, Observer {

        val resource = it?.contentIfNotHandled?
        if (resource == null) return

        val session = resource.data?

        if (resource.status) {
                "Hi, " + session.displayName,

            val sharedPref = PreferenceManager
            val editor = sharedPref.edit()

            editor.putString(getString(R.string.user_id), session.email).apply()
            editor.putString(getString(R.string.user_name), session.email).apply()


        } else {
                "Error, " + resource.message,

private fun onClickLogin(view: View) {

    view.loginButton.setOnClickListener {

        val emailAddress = view.emailTextInputEditText.text.toString()
        val password = view.passwordTextInputEditText.text.toString()

        viewmodel.generalLogin(emailAddress, password)
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