As i am working in a Project where i want to rewrite the Uni to Multi for a method "findall" to get all the mongodb Document from a collection. I tried to rewrite but not able to find a solution
original:
public Uni<List<Book>> findAll(List<String> authors)
{
return getCollection().
find(Filters.all("authors",authors)).map(Book::from).collectItems().asList();
}
What i tried (But not working)
public Multi<Book> findAll(List<String> authors)
{
return getCollection().find(Filters.all("authors",authors)).transform().
byFilteringItemsWith(Objects::nonNull).onCompletion().ifEmpty().
failWith(new NoSuchElementException("couldn't find the Authors")).onItem().transform(Book::from);
}
I suppose you are using the ReactiveMongoClient provided by Quarkus.
In this case, your method should be:
ReactiveMongoClient client;
public ReactiveMongoCollection<Book> getCollection() {
return client.getDatabase("db").getCollection("books", Book.class);
}
public Multi<Book> findAll(List<String> authors) {
return getCollection()
.find(Filters.all("authors",authors))
.onItem().transform(Book::from)
.onCompletion().ifEmpty()
.failWith(new NoSuchElementException("..."));
}
You don't need to do thebyFilteringItemsWith, as a Multi cannot contain null items.
Related
Okay so at work we are developing a system using MVC C# & MongoDB. When first developing we decided it would probably be a good idea to follow the Repository pattern (what a pain in the ass!), here is the code to give an idea of what is currently implemented.
The MongoRepository class:
public class MongoRepository { }
public class MongoRepository<T> : MongoRepository, IRepository<T>
where T : IEntity
{
private MongoClient _client;
private IMongoDatabase _database;
private IMongoCollection<T> _collection;
public string StoreName {
get {
return typeof(T).Name;
}
}
}
public MongoRepository() {
_client = new MongoClient(ConfigurationManager.AppSettings["MongoDatabaseURL"]);
_database = _client.GetDatabase(ConfigurationManager.AppSettings["MongoDatabaseName"]);
/* misc code here */
Init();
}
public void Init() {
_collection = _database.GetCollection<T>(StoreName);
}
public IQueryable<T> SearchFor() {
return _collection.AsQueryable<T>();
}
}
The IRepository interface class:
public interface IRepository { }
public interface IRepository<T> : IRepository
where T : IEntity
{
string StoreNamePrepend { get; set; }
string StoreNameAppend { get; set; }
IQueryable<T> SearchFor();
/* misc code */
}
The repository is then instantiated using Ninject but without that it would look something like this (just to make this a simpler example):
MongoRepository<Client> clientCol = new MongoRepository<Client>();
Here is the code used for the search pages which is used to feed into a controller action which outputs JSON for a table with DataTables to read. Please note that the following uses DynamicLinq so that the linq can be built from string input:
tmpFinalList = clientCol
.SearchFor()
.OrderBy(tmpOrder) // tmpOrder = "ClientDescription DESC"
.Skip(Start) // Start = 99900
.Take(PageLength) // PageLength = 10
.ToList();
Now the problem is that if the collection has a lot of records (99,905 to be exact) everything works fine if the data in a field isn't very large for example our Key field is a 5 character fixed length string and I can Skip and Take fine using this query. However if it is something like ClientDescription can be much longer I can 'Sort' fine and 'Take' fine from the front of the query (i.e. Page 1) however when I page to the end with Skip = 99900 & Take = 10 it gives the following memory error:
An exception of type 'MongoDB.Driver.MongoCommandException' occurred
in MongoDB.Driver.dll but was not handled in user code
Additional information: Command aggregate failed: exception: Sort
exceeded memory limit of 104857600 bytes, but did not opt in to
external sorting. Aborting operation. Pass allowDiskUse:true to opt
in..
Okay so that is easy to understand I guess. I have had a look online and mostly everything that is suggested is to use Aggregation and "allowDiskUse:true" however since I use IQueryable in IRepository I cannot start using IAggregateFluent<> because you would then need to expose MongoDB related classes to IRepository which would go against IoC principals.
Is there any way to force IQueryable to use this or does anyone know of a way for me to access IAggregateFluent without going against IoC principals?
One thing of interest to me is why the sort works for page 1 (Start = 0, Take = 10) but then fails when I search to the end ... surely everything must be sorted for me to be able to get the items in order for Page 1 but shouldn't (Start = 99900, Take = 10) just need the same amount of 'sorting' and MongoDB should just send me the last 5 or so records. Why doesn't this error happen when both sorts are done?
ANSWER
Okay so with the help of #craig-wilson upgrading to the newest version of MongoDB C# drivers and changing the following in MongoRepository will fix the problem:
public IQueryable<T> SearchFor() {
return _collection.AsQueryable<T>(new AggregateOptions { AllowDiskUse = true });
}
I was getting a System.MissingMethodException but this was caused by other copies of the MongoDB drivers needing updated as well.
When creating the IQueryable from an IMongoCollection, you can pass in the AggregateOptions which allow you to set AllowDiskUse.
https://github.com/mongodb/mongo-csharp-driver/blob/master/src/MongoDB.Driver/IMongoCollectionExtensions.cs#L53
i have an oData enabled web api function
[EnableQuery()]
public IQueryable<StoreCommand> Get()
{
return _storeCommandService.GetAllStoreCommands().AsQueryable();
}
the service layer calling Mongodb based Repository pattern's implementation.
public IEnumerable<StoreCommand> GetAllStoreCommands()
{
return _uow.StoreCommands.GetAll();
}
where GetAll is implemented in Repository layer like
public IList<TEntity> GetAll()
{
return _collection.FindAllAs<TEntity>().ToList();
}
where _collection is a MongoCollection of c# driver.
when i make a call like
http://localhost:xxxx/api/storeCommandsrest?$skip=0&$top=10&$orderby=Name
i get top 10 records but it pulls all the records from the DB and send me back top 10.
Please guide how we can pull only the required set from the DB.
Comment moved to answer:
You aren't returning an IQueryable from GetAllStoreCommands(). Your return type must be an IQueryable(). To get that from the driver, it should be _collection.AsQueryable().
I can't really understand when to use flatmap instead of map, nor do I find a good example.
Can you come up with a good scenrio to choose flat map over map?
Thanks.
For example, we want to do 2 requests, A and B, over web. However, request B must be requested after request A finishes because request B needs some result of request A. This is a good scenrio of flatMap. The example codes are as follow:
interface Movie {
}
interface UserInfo {
List<Long> getFavoriteMovies();
}
public Observable<UserInfo> requestUserInfo(long userId) {
// ...
}
public Observable<List<Movie>> requestMovieList(List<Long> movieIds) {
// ...
}
public Observable<List<Movie>> requestUserMovieList(long userId) {
return requestUserInfo(userId).flatMap(new Func1<UserInfo, Observable<List<Movie>>>() {
#Override
public Observable<List<Movie>> call(UserInfo user) {
return requestMovieList(user.getFavoriteMovies());
}
});
}
In addition, Ben Christensen's slide has some good examples of RxJava: https://speakerdeck.com/benjchristensen/rxjava-goto-aarhus-2013
I am currently trying to persist the following class with the GORM MongoDB plugin for grails:
class Result {
String url
def Result(){
}
static constraints = {
}
static mapWith="mongo"
static mapping = {
collection "results"
database "crawl"
}
}
The code I'm running to persist this class is the following:
class ResultIntegrationTests {
#Before
void setUp() {
}
#After
void tearDown() {
}
#Test
void testSomething() {
Result r = new Result();
r.setUrl("http://heise.de")
r.getMetaClass().setProperty("title", "This is how it ends!")
println(r.getTitle())
r.save(flush:true)
}
}
This is the result in MongoDB:
{ "_id" : NumberLong(1), "url" : "http://heise.de", "version" : 0 }#
Now the url is properly persisted with MongoDB but the dynamic property somehow is not seen by the mapper - although the println(r.getTitle()) works perfectly fine.
I am new to groovy so I thought that someone with a little more experience could help me out with this problem. Is there a way to make this dynamically added property visible to the mapping facility? If yes how can I do that?
Thanks a lot for any advice...
Rather than adding random properties to the metaClass and hoping that Grails will both scan the metaClass looking for your random properties and then persist them, why not just add a Map to your domain class, (or a new Key/Value domain class which Result can hasMany) so you can add random extra properties to it as you want.
try this doc
#Test
void testSomething() {
Result r = new Result();
r.url = "http://heise.de"
r.['title'] = "This is how it ends!" //edit: forgot the subscript
println r.['title']
r.save(flush:true)
}
BTW, Instead of using gorm or hibernate you can always use directly java api / gmongo.
In my API, I'd like to have routes like GET /api/v1/widgets/1,2,3 and GET /api/v1/widgets/best-widget,major-widget,bob-the-widget
public class WidgetsController : MyApiController
{
public ActionResult Show(IEnumerable<int> ids)
{
}
public ActionResult Show(IEnumerable<string> names)
{
}
}
I've got routes set up to get me to the action, but I can't figure out how to turn 1,2,3 into new List<int>(){1, 2, 3} and so on. Of course, I could just take a string and parse it in my action, but I'd like to avoid going that route.
One thing that came to mind was to put something in the OnActionExecuting method, but then I wasn't sure exactly what to put in there (I could hack something together, obviously, but I'm trying to write something reusable.)
The main questions I have are how to know whether I need to do anything at all (sometimes the ValueProviders upstream will have figured everything out), and how to handle figuring out the type to cast to (e.g., how do I know that in this case I need to go to a collection of ints, or a collection of strings, and then how do I do that?)
By the way, I had the idea of implementing a ValueProvider as well, but got lost on similar questions.
I can't figure out how to turn 1,2,3 into new List(){1, 2, 3} and so on.
To avoid polluting each controller action that needs to receive this parameter I would recommend a custom model binder:
public class IdsModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var result = base.BindModel(controllerContext, bindingContext);
var ids = bindingContext.ValueProvider.GetValue("ids");
if (ids != null)
{
return ids.AttemptedValue
.Split(',')
.Select(id => int.Parse(id))
.ToList();
}
return result;
}
}
and then register the model binder in Application_Start:
ModelBinders.Binders.Add(typeof(IEnumerable<int>), new IdsModelBinder());
and finally your controller action might look like this (and from what I can see in your question it already does look like this :-)):
public ActionResult Show(IEnumerable<int> ids)
{
...
}
and the custom model binder will take care for parsing the ids route token to the corresponding IEnumerable<int> value.
You could do the same with the IEnumerable<string> where you would simply remove the .Select clause in the corresponding model binder.
if your URL was
/api/v1/widgets/Show?names=best-widget&names=major-widget&names=bob-the-widget
This would bind neatly by itself :)
No need to override modelbinders in this case.
The querystring-variable names will bind to your Show-method_
public ActionResult Show(IEnumerable<string> names)
Hope this helps!
I'm relatively new to ASP.Net MVC and so I'm not sure if there is an easier way of doing this or not, however my approach would be to do something like the following:
public class WidgetsController : MyApiController
{
public ActionResult Show(string ids)
{
List<int> parsedIds = new List<int>();
foreach (var id in ids.Split(','))
{
parsedIds.Add(int.Parse(id));
}
return Show(parsedIds);
}
private ActionResult Show(List<int> ids);
}
You might also want to add some more sophisticated error handling for cases where the IDs entered can't be parsed, but thats the general approach I would use.