I know automatic insertion happens to domainevententry table as soon as we do aggregatelifecycle.apply(event) in axon framework what action triggers an insert in domainevententry table and what triggers a publish to a kafka topic in axon framework and how can we control what values goes into domainevententry table
Explaining this point by point, in full detail, would be a bit much to go over.
On top of that, like #Pipetus stated, it is still unclear what your intent is with this question. It's highly recommend to be as specific in your posts as possible, stated the problem space, where you are coming from and where you want to get too.
Regardless, pointers you can look for when it comes to "how does this work" are the (aggregate) Repository implementations, the options of EventStorageEngines provided, the UnitOfWork used to deal with message transactions and the phases the UnitOfWork transitions.
In short, all of these are described in the Reference Guide of Axon. I'd recommend reading up here and updating your question accordingly so that more specifics can be provided to you.
Related
We recently introduced GraphQL to our project, I've never used it before, however I like it a lot.
We decided to go with the HotChocolate library for .NET Core and Apollo for client side.
One thing I am not quite sure is about mutations, specifically peforming updates and partial updates with mutations.
I read somewhere that the practice is and that I should stick with creating specific mutation for each update, for instance updateUsername(), updateAddress(), updateCity() all of them should have specific mutation.
Issue with that is that my codebase will grow enormously if I decide to go in that direction, as we are very much data driven, with a lot of tables and columns per table.
Another question is, how to handle nullable properties, I can create a mutation which accepts some input object, but I'll end up with my entity being overwritten and all nullable properties not provided on the calling end will be set to null.
Is there a way to handle this update partially or I should go with specific update mutation for each property I want updated?
I think you understood the best practice around specific mutations wrong. It's less "have one mutation to update one field" and more "have specific mutations that encapsulate actions in your domain". A concrete example would be creating an "addItemToBasket" mutation, instead of having 3 mutations that update the individual tables related to your shopping basket, etc.
GraphQL is very much centered around front-end development, so your mutations should, in general, closely resemble actions a user can perform in your front-end. E.g. your front-end has an "Add to basket" button and your backend has an "addItemToBasket" mutation that resembles the action of placing an item in the user's basket.
If you design your mutations with this in mind, most of the time you shouldn't be having an issue with partial updates, since the mutation knows exactly what's to do and you are not just letting the user of your schema update fields at will.
If for whatever reason you need to have these partial updates, you likely won't get around implementing the patching yourself, unless your data provider supports it. Meaning you will have to have an input object type with nullable properties and your mutation that decides which fields have been changed and changing them using your data provider.
That being said, there's also a proposal for patching types in the Hot Chocolate repository that should simplify the patching part: https://github.com/ChilliCream/hotchocolate/issues/1326
for instance updateUsername(), updateAddress(), updateCity() all of them should have specific mutation.
Issue with that is that my codebase will grow enormously if I decide
to go in that direction, as we are very much data driven, with a lot
of tables and columns per table.
Correct. That's practically impossible to follow that way for more or less big data-driven applications.
Consider how we implement the patching in our API here. Also consider following the discussion about the patching feature in HotChocolate github thread. Hope, that helps!
I am new to android and java and working on an app that has a few remaining problems that I haven't resolved yet.
I have a main activity that is a viewPager, with each page being a fragment. If the 4 fragments 3 are extended from ListFragments and one from PreferencesFragment.
The ListFragments have CursorAdapters to get data to and from SQLite databases through providers.
I am able to get data into the database, insert, modify and query the data correctly and fill the list views ok.
My preference setting are to choose different ways of viewing the data in the database.
Not knowing how to do this, I have implemented a process where I modify the cursorLoader query to the provider with a number of different choices of the "WHERE" clause. I have worked out the logic for the preferences as they exist now, implemented the code but had some difficulty finding what to try to trigger the refresh of the ListView.
Since the "dataset" hasn't really changed, no trigger can come from there, plus that would just use the same cursor as it currently exists to run the query again and return the same results (or be smart enough to know that it doesn't need to run).
On Stack Overflow I did find a couple of references to a similar implementation that suggested reStarting the cursor loader, which would then on the reStart read the current values in the stored Preferences file, create a now modified WHERE clause that will show the sub-set of data as specified in the preference settings.
In testing the app now, even with the reStart of the cursorLoader, the ListView isn't getting refreshed.
The only time I can get it to work right is restarting the app. If I stop the app and restart it, the new values are used and the ListView presents as the preferences dictate.
In looking through Stack Overflow and the Android site, I did find another set of APIs that might have been a more natural fit for what I am trying to do, namely the Filter APIs.
First question then would be, did I go in the wrong direction on how to control the "filtered" view of the datbase. Is filtering a better approach and a recommended way of
doing what I am trying to do?
Second question would be related to the fragment lifecycle of my ListFragments to achieve this CursorLoader update.
Thanks for any input on the topic.
-Dan
Found my problem here.
Two things, the way I am trying filtering is working and from what I have seen in the
Android development site, a reference there indicated that the filtering capability is
already implemented in the CursorAdapter, CursorLoader classes I am using.
When my preference settings changed, I did a reStart of the cursorLoader, but had restarted the wrong one.
Problem solved. Any input on is there a better way would be appreciated.
Regards, Dan
I have an Article and Comment entity (oneToMany)
On Comment prepersist lifecycle event I would like to count how many comments there are for this article and update Article's comment_count field.
If I understand symfony2 approach correctly, I need to write a service for this. Let's call it CommentCountManager.
My question is: How exactly do I make container available in entity so that I can get the CommentCountManager and triger the funciton that count comment for given article, and how do I access Doctrine's entity manager in my CommentCountManager so that I can actually run queries there?
Am I on the right path?
Your help is greatly appreciated.
You don't need to store the comments count in a separate column — you can count them on output. What you are trying to do is denormalization and I recommend avoiding it unless you absolutely need it for performance reasons — and only when you are sure that that part is causing the problems. But even then, query optimization and caching are much better alternatives to denormalization.
Making entities aware of the container is a bad idea too. If you need this, then you are doing something wrong.
To access an entity manager in a service, you need to inject it.
I am struggling with the following use-case:
User amends an existing order. The order is complex - lots of related 'entities' (addresses, post options, suppliers, makes, models, various items etc). Across multiple http posts.
User wants to discard the changes.
--
I have an order entity and as the user is editing this I am making various changes to the entity associations e.g changing order.address, order.items.add(item)...
In a single post this is fine, but across posts I don't know how best store state. If I store the entities then I cannot save the changes as they are across different data contexts. I have read that it is bad practice to store the data context in the session state i.e. long-lived context. I can't save changes after each edit/post because I cannot roll-back (?). I really would like to work with the entities during the editing process rather than one big save at the end (taking UI settings and applying these in one chunk).
This must be a pretty common problem - it's driving me mad. Any help really appreciated.
Cheers!
We have a similar problem where we are building a complex business object through a multi-page wizard.
Instead of creating a partially complete business object at each step of the wizard, we create a dedicated wizard object that looks pretty similar to the business object, populate that through the wizard. At each step in the wizard, the wizard object is saved into the database. At the end the user can accept it and it is converted to a real business object and then becomes visible to everyone else, or they can bin it and no-one else ever knows it existed.
If this kind of approach was not suitable, I suspect you're looking at some kind of difference tracking, either at the entity or database levels. Neither are simple to implement, work with or manage in a system. The former would be some kind of calculation and storage of n changes to the entities and developing an algorithm to undo them, the latter depends on your RDBMS, but might include versioned rows or similar.
Yes its pretty much common for us. In most scenarios we use the MVC approach. Even without the actual ASP .NET MVC Projects, we use similar ViewModel with our Views/Pages/Scenarios etc. where there is no direct/single entity mapping to the Business Layer (in other words, Business.Entities). This is pretty much similar to DTOs.
It is always easy to use Disconnected EF. We retrieve data and discard the context, then transform the Entities into ViewModels/DTOs if necessary. When you need to persist changes, all you have to do is to create a new context, find the latest entity instance do the changes.
The Views/Pages/Controllers will be managing these ViewModels/DTOs. Tracking Changed and Deleted content can be done by introducing a HistoryList<T> (you can extend a List<T> to implement this).
Once done, using a Controller/Workflow/Component you can observe the ViewModel/DTO and do the necessary changes to your Entities using a new Context to retrieve and persist.
It involves a bit of a coding and I would say its not a perfect solution since it has its own pros and cons.
/KP
I am working on a design spec for a new application that will be heavily workflow driven.
Before I re-invent the wheel, is there a decent lightweight workflow engine that plugs into ASP.NET already around?
Basically, I'm looking for something that handles moving through a defined set of workflow pages while handling state management automatically.
If this isn't around already, I'll definitely try to abstract the engine from my app and put it on codeplex, as it would be really handy.
Any suggestions?
Note: .NET 2.0, so no WWF, though I think WWF is overkill for my needs.
EDIT: Seems like there is a legitimate need for this, and there isn't a product out there...So I might build this.
Here is what I'm picturing:
Custom Page class called WebFlowPage
All WebFlowPage's are registered in a Workflow mapper.
Each WebFlowPage has some form of state object.
A HttpHandler handles picking the appropriate WebFlowPage based upon the workflow, and populating it from the state object.
Is the workflow dynamic, or static?
If the workflows are simple, you could roll your own workflow engine.
In certain situations, it can be fairly simple, and just a couple of data tables to handle the rules, processing and state.
Alot of workflow engines are built for large scale processing (credit card applications, for example). For small scale, you should at least consider your own, which would eliminate the overhead and dependency of/on an engine.
Not sure exactly what you wish to do here, but Ra-Ajax can easily keep state at least if you want your solution ajaxified...
For reference purposes you might want to check out the Ajax Calendar sample or even the (banalistically implemented) Ajax Wizard sample. It surely beats the hell out of doing it with JavaScript...
And every time you "do something" you're in "server-land" which means you can store temporaries all the time as you wish...
The project is LGPL
(PS!
Yes I do work with it)
Building a custom workflow engine is not trivial, although it may seem simple at first. We've tried that. It depends a lot on the complexity of the logic you need it to cover.
Given the current state of the Windows Workflow Foundation and the lack of another framework that abstracts the workflow concepts, I would choose WF if you need complex logic, asynchronous handling or branches in your workflows.
Tracking your state through the workflow can be accomplished by carrying some kind of xml payload or storing the state in a database,
If your workflow is actually a sequential set of forms that need to be filled in by the user, tracking the steps and guiding the user to the next step can be accomplished with some simple custom solution.
You could take a look at the InRule engine too.
Also, there is nxBRE.
These too are mostly used for business rules.
InRule is proprietary, whereas nxBRE supports RuleML (the defacto standard).
You might need to make your own implementation for the pages, and use the rule engine as the "structure".
At this moment, I know that Sharepoint 2007 supports page workflows (using WF), but this would imply using .NET Framework 3 and deployng sharepoint.
My suggestion would be to use whatever you find more light and easier to use.
I think the term "workflow" is very open to interpretation. I have been working lately with a type of workflow that is very different from what you seem to be describing. Mine is a state machine based workflow where the state of a particular record determines what actions a user can take to move the record to the next step in the business process. So "workflow" in this instance means how the record flows from one state to another until it is finally completed.
Your usage of workflow seems to have more to do with moving a user from one page to another in a linear multi-step process, which is a completely different use case (correct me if I'm wrong). So before coming up with a general purpose "workflow" engine that anyone could use, I would recommend defining a little bit better exactly what types of situations this system would handle.
I've been using this for a few months http://objectflow.codeplex.com. Not asp specific but it may fit your needs
While browsing the web for some workflow & BPM resources, I found the following project: NetBPM. Unfortunately, the project seems to be stopped.
I don't think there is a workflow engine that will automatically handle state for you, but if you are moving through a set of pages like a process such as checkout on an ecommerce site, perhaps the ASP.NET wizard control could help you?
There are few workflow options. "Aspose" and "Skelta" are the offers I´m evaluating.
Fábio
you can use WorkFlow Engine, just read the document and run the Demo.
all of the features you need for a dynamic workflow engine they added in there.