getsong | Download any song mp3 with no dependencies except ffmpeg | Download Utils library

For SongEntity's @EqualsAndHashCode(onlyExplicitlyIncluded = true), you don't have any explicitly included annotations. You have a few listed to Exclude, but based on the docs at https://projectlombok.org/features/EqualsAndHashCode, it seems to require you explicitly mark them as Included when you use this flag.

I'm not 100% sure what Lombok does when you put this flag at the class level but then don't explicitly include anything, but it seems like an invalid state and may be messing up your Equals and Hashcode and consequently messing up ability to track the items in the HashSet bucket that represents the songs that you're adding to.

So I'd start by fixing this so your Equals/HashCode is correct. Which looks like you'd want to either remove the onlyExplicitlyIncluded=true settings altogether OR you actually add specific Includes.

Here is a thread that talks about using explicit Includes if you want to stick with that route: How to use @EqualsAndHashCode With Include - Lombok

Also, why do you have @Transient annotations on your relationships? That annotation usually tells the EntityManager to ignore the content it's attached to. In your case, if you're adding something to the Set but marking the Set as @Transient, then intuitively it should not affect in the Database. Suggest you remove those annotations where you want changes to objects in the relationships/sets to actually be reflected in the database.

Try calling setState or using a FutureBuilder.

Firstly I think you should take a look at using proper Android lifecycle scopes to launch your coroutines. If you create a scope in an Android component like an Activity then you should look into cancelling it yourself when the activity is destroyed. There is some good documentation here which I would recommend taking a look at.

In regards to your actual question, you're on the right track!

First of all, your ViewModel should expose some LiveData as it does in your code but should launch a coroutine scope in its init block which fetches the data from the endpoint. Then when it has fetched it, you should only then set the LiveData value to your loaded data.

In your activity, instead of trying to launch a coroutine to setup your RecyclerView, set it up beforehand with just the LayoutManager and then start observing the exposed LiveData. Then when the data being observed is changed, only then set the adapter to the RecyclerView.

A quick pseudocode overview might help:

ViewModel

Try adding.

1. Add spring.jpa.open-in-view=false to the application.properties to have LazyInitializationException. It will help to build good queries. What is this spring.jpa.open-in-view=true property in Spring Boot?

2. Load PlayList with songs using JPQL query with LEFT JOIN FETCH to fetch songs with the list. So songs will be already loaded and playList in the song will be lazy. @EntityGraph can be used also.

@Model.sortSongs(Convert.ToInt32(@Html.DisplayFor(modelItem => item.id)),"U")

You are not sending request to the method. Route in Razor pages is different from that in MVC. The handler should be start with OnGet or OnPost, to represent it a get or post method. Here you can use anchor instead of button, like below:

Index.cshtml:

I think you're pretty close. But you're missing a return in your recursive call. A recursive function should either return data, or call itself again.

Let's refactor that into an async function, and also ensure that we use tail recursion.

You could use Promise.allSettled. From the MDN docs

The Promise.allSettled() method returns a promise that resolves after all of the given promises have either fulfilled or rejected, with an array of objects that each describes the outcome of each promise.

Store the promises in an array, don't await them and pass that array to Promise.allSettled. With this all your errors (if any) will be stored and returned to you in array at the end of the operation.

java.time is almost always where you want to go when you have time/date stuff to do.