I have the following in my application:
Action Orm entity (From telerik open access)
Repository(Of Action)
AppService(Holds an instance of the repository)
when I need to save an instance, I send the instance to the AppService. the AppService then calls a validator to validate the instance to save. the validator is based on http://codeinsanity.com/archive/2008/12/02/a-framework-for-validation-and-business-rules.aspx
(full code on https://github.com/riteshrao/ncommon)
so basically my save function in the AppService looks like this
Public Sub AddAction(ByVal Item As Data.Model.Action)
Contract.Requires(Of ArgumentNullException)(Item IsNot Nothing, "Item is nothing.")
Dim validateResult As Rules.ValidationResult = _ActionValidator.Validate(Item)
If Not validateResult.IsValid Then
Throw New Validation.ValidationException(validateResult)
End If
Try
_ActionRepository.Add(Item)
_unitOfWork.SaveChanges()
Catch ex As Exception
_unitOfWork.ClearChanges()
Throw New DataServiceException(ex.Message, ex)
End Try
End Sub
for checking properties of the Action item the sample code works great. my question begins when i need to make sure that the same action is not added twice to the DB for the same customer (ie. id is difference, name is the same and customer is the same)
as I see it I have a few options:
option 1: check for a duplicate action using something like
function(validatedItem) item.Customer.Actions.Any(function(item) item.id<>validatedItem.id andalso item.name=validatedItem.name))
basically I go from the action being saved back to the customer and then back to all his actions and check if any action exists with a different id and same name
the down sides are:
a. for this to work, when accessing the customer property of the item, the entire customer object is read from DB which is redundant in this case
b. the Any function is being evaluated on the client as item.Customer.Actions returns IList(Of Action)
Option 2: let the validation class have access to the action repository. then i could simply do something like
'assume I already have validatedItem
repository.Any(function(item) item.id<>validatedItem.id and item.customerid=validatedItem.customerid and item.name=validatedItem.name)
this will result in an Exists query being sent to the DB but the downside(?) is that the validation framework should not access the repository directly (as far as I have seen in the very few examples i could find that do use validation and ORM)
Option 3: let the validation class have access to the AppService and use the AppService to check for existence of a duplicate.
problems:
a. I create a circular reference (AppService->Validation Class->AppService)
b. I need to create a lot of useless functions in the AppService for loading items based on criteria that is only relevant for the validation
Any ideas what is the best course here?
The simplest is not to check duplicates in the database from your domain.
When a collection of entities is part of you aggregate then it is a non-issue since you would not permit the duplicate to be added to the collection. Since the aggregate is stored as a whole you would never run into the problem.
For scenarios where you do not want a duplicate, say, e-mail address and no collection of the entities is represented by an aggregate (such as the Users in a system) you can just let the database enforce the uniqueness. Simply pick up the exception and report back. In many instances your validation would not be able to enforce the uniqueness simply because it doesn't have/implement the required locks that a database system would have.
So I'd simply leave that up to the database.
Related
I am writing a Post PLugin changing the owner. When the owner has a substitution manager, the owner is changed to the substitution manager. I tried a service.Update and an AssignRequest, but these throw an exception.
When I post the request my entity cannot update (and then throws "The request channel time out while waiting for reply after 10:00:00"). But like I see there is no recursion, because when I logged it I have only one repetition of log and it has stopped before or on line with update.
var assignedIncident = new AssignRequest
{
Assignee = substManagerRef, //get it throw another method, alreay checked in test it`s correct
Target = new EntityReference ("incident", incedentId)
};
service.Execute(assignedIncident);
I tried to write target in another way
Target = postEntityImage.ToEntityReference()
I tried to write simple update but the problem is the same.
Entity incident = new Entity("incident" , incidentId);
incident["ownerid"] = substManagerRef:
service.Update(incident);
Can somebody help me with that? Or maybe show the way to solve it)
The plugin is triggering itself and gets in a loop. The system only allows a maximum of 8 calls deep within plugins and that is the reason it throws an error and rolls back the transaction.
To solve this issue redesign your plugin in the following way:
Register your plugin on the Update message of your entity in the PreValidation stage.
In the plugin pick up the Target property from the InputParameters collection.
This is an Entity type. Modify or set the ownerid attribute on this Entity object.
That is all. You do not need to do an update, your modification is now passed into the plugin pipeline.
Note: for EntityReference attributes this technique only works when your plugin is registered in the PreValidation stage. For other regular attributes it also works in the PreOperation stage.
I have a Document entity. To edit a document you must acquire a DocumentLock.
Request API to edit a document looks like below. edit=true allows to fetch the record from database with 'FOR UPDATE`.
GET /api/document/123?edit=true
In Back end side, we do like this (of course over simplified),
Document document = documentRepository.getOne(documentId) //<--- (1)
if(document == null){ //<--- (2) This is always false
//Throw exception
}
DocumentLock dl = DocumentLock.builder()
.lockedBy(user)
.lockedAt(NOW)
.document(document)
.build()
documentLockRepository.save(dl);
We are using getOne() because we do not need to fetch whole document from database, we are just creating a relation with DocumentLock object.
Question is, how to ensure the document actually exists? Because getOne() will always return the proxy and I do not see any obvious way to check if the record exists in databse.
Versions:
spring-data-jpa: 2.2.6.RELEASE
hibernate: 5.4.12
Update: removed additional questions.
Use findById or existsById. Yes they do access the database. That is the point of it, isn't it?
getOne is explicitly for use cases where you already know the entity exists and only need the id wrapped in something that looks like the entity.
If your repository returning value or its transactional management is confusing, you should check your repository codes and entity class design even session configurations that used for querying or even your Datastore design because everything looks fine in this code fragment
Data validation should occur at the following places in a web-application:
Client-side: browser. To speed up user error reporting
Server-side: controller. To check if user input is syntactically valid (no sql injections, for example, valid format for all passed in fields, all required fields are filled in etc.)
Server-side: model (domain layer). To check if user input is domain-wise valid (no duplicating usernames, account balance is not negative etc.)
I am currently a DDD fan, so I have UI and Domain layers separated in my applications.
I am also trying to follow the rule, that domain model should never contain an invalid data.
So, how do you design validation mechanism in your application so that validation errors, that take place in the domain, propagate properly to the client? For example, when domain model raises an exception about duplicate username, how to correctly bind that exception to the submitted form?
Some article, that inspired this question, can be found here: http://verraes.net/2015/02/form-command-model-validation/
I've seen no such mechanisms in web frameworks known to me. What first springs into my mind is to make domain model include the name of the field, causing exception, in the exception data and then in the UI layer provide a map between form data fields and model data fields to properly show the error in it's context for a user. Is this approach valid? It looks shaky... Are there some examples of better design?
Although not exactly the same question as this one, I think the answer is the same:
Encapsulate the validation logic into a reusable class. These classes are usually called specifications, validators or rules and are part of the domain.
Now you can use these specifications in both the model and the service layer.
If your UI uses the same technology as the model, you may also be able to use the specifications there (e.g. when using NodeJS on the server, you're able to write the specs in JS and use them in the browser, too).
Edit - additional information after the chat
Create fine-grained specifications, so that you are able to display appropriate error messages if a spec fails.
Don't make business rules or specifications aware of form fields.
Only create specs for business rules, not for basic input validation tasks (e.g. checking for null).
I want to share the approach used by us in one DDD project.
We created a BaseClass having fields ErrorId &
ErrorMessage.
Every DomainModel derive from this BaseClass & thus have a two extra fields ErrorId & ErrorMessage available from
BaseClass.
Whenever exception occurs we handle exception(Log in server, take appropriate steps for compensating logic & fetch User Friendly message from client location based localized Resource file for message ) then propagate data as simple flow without raising or throwing exception.
At client side check if ErrorMessage is not null then show error.
It's basic simple approach we followed from start of project.
If it's new project this is least complicated & efficient approach, but if you doing changes in big old project this might not help as changes are big.
For validation at each field level, use Validation Application Block from Enterprise Library.
It can be used as :
Decorate domain model properties with proper attributes like:
public class AttributeCustomer
{
[NotNullValidator(MessageTemplate = "Customer must have valid no")]
[StringLengthValidator(5, RangeBoundaryType.Inclusive,
5, RangeBoundaryType.Inclusive,
MessageTemplate = "Customer no must have {3} characters.")]
[RegexValidator("[A-Z]{2}[0-9]{3}",
MessageTemplate = "Customer no must be 2 capital letters and 3 numbers.")]
public string CustomerNo { get; set; }
}
Create validator instance like:
Validator<AttributeCustomer> cusValidator =
valFactory.CreateValidator<AttributeCustomer>();
Use object & do validation as :
customer.CustomerNo = "AB123";
customer.FirstName = "Brown";
customer.LastName = "Green";
customer.BirthDate = "1980-01-01";
customer.CustomerType = "VIP";
ValidationResults valResults = cusValidator.Validate(customer);
Check Validation results as:
if (valResults.IsValid)
{
MessageBox.Show("Customer information is valid");
}
else
{
foreach (ValidationResult item in valResults)
{
// Put your validation detection logic
}
}
Code example is taken from Microsoft Enterprise Library 5.0 - Introduction to Validation Block
This links will help to understand Validation Application Block:
http://www.codeproject.com/Articles/256355/Microsoft-Enterprise-Library-Introduction-to-V
https://msdn.microsoft.com/en-in/library/ff650131.aspx
https://msdn.microsoft.com/library/cc467894.aspx
I have an external list in SharePoint that references a BCDM I created inside visual studio. The entity as an ID that is auto generated in the database, which means it's read-only.
Create and read method works fine, I'm trying to implement the update method. I have set an input parameter that match my entity and I'm getting this error.
Failed to update a list item for this external list based on the Entity(External Content Type) ‘Notification’ in EntityNamespace ‘Namespace’. Details: The TypeDescriptor with name ‘Id’ in the Method ‘Microsoft.SharePoint.BusinessData.MetadataModel.Static.Method’ on Entity (External Content Type) with Name ‘Namespace’ in Namespace ‘Notification’ is marked ‘PreUpdaterField’, but is contained by another TypeDescriptor marked ‘PreUpdaterField’.
I tried every possible combinaison to make this work, make the id type descriptor read only, pre-updater field = true/ false/, updater field = true/false, removing it, adding another parameter outside the entity. NOTHING WORKS !!! Obviously, I'm about to commit a murder as something so simple just turned out to be the biggest waste of time in my programmation history. What can I do to make this works??
This has been resolved and is explained here:
http://www.dotnetmikael.com/2014/02/sharepoint-2013-bcdm-with-visual-studio.html
In my application, I have cross-entity validation logic that requires me to look at the entire change set and I'm doing this using the BeforeSaveEntities override.
I can construct the right logic by examining the saveMap parameter, but what am I supposed to do if I find something invalid?
If I throw an exception, like I would for single entity validation in the BeforeSaveEntity override, the whole save is aborted and the error is reported to the client. But some of the entities might be valid so I would want to save those and only abort the invalid parts.
Because BeforeSaveEntities returns a saveMap, I think I should be able to remove the invalid entities from the change set and continue to save the valid entities, but then how do I report the invalid parts to the client?
Is it possible to do a partial save of only the valid entities and at the same time, report a sensible error to the client to describe the parts of the save that failed?
Jay told you the way it is.
I wouldn't hold my breath waiting for Breeze to change because I think yours is a rare scenario and it isn't one we would want to encourage anyway.
But I'm weird and I can't stop thinking what I'd do if were you and I absolutely HAD to do it. I might try something like this.
Warning: this is pseudo-code and I'm making this up. I do not recommend or warrant this
Create a custom MyCustomEFContextProvider that derives from EFContextProvider.
Give it an ErrorEntities property to hold the error object
Override (shadow) the SaveChanges method with another that delegates to the base
public new CustomSaveResult SaveChanges(JObject saveBundle,
TransactionSettings transactionSettings = null) {
var result = base.SaveChanges(saveBundle, transactionSettings);
// learn about CustomSaveResult below
return new CustomSaveResult(this.ErrorEntities, result);
}
Catch an invalid entity inside BeforeSaveEntities
Pass it with error message to your custom ErrorEntities property
You get to that property via the EntityInfo instance as in
((MyCustomEFContextProvider) info.ContextProvider).ErrorEntities.Add(new ErrorEntity(info, message));
Remove the invalid entity from the SaveMap so it won't be included in the actual save
Let the save continue
The second line of your override SaveChanges method creates a new instance of your CustomSaveResult from the standard one and returns that to the caller.
public class CustomSaveResult : SaveResult {
public List ErrorEntities;
public CustomSaveResult(List errorEntities, SaveResult result){
// copy over everything
this.Entities = result.Entities;
this.KeyMappings = result.KeyMappings;
this.Errors = this.Errors;
// and now your error stuff
this.ErrorEntities = errorEntities;
}
}
Let's assume the caller is your Web API controller's SaveChanges method. Well you don't have to change a thing but you might make it clear by explicitly returning your custom SaveResult:
readonly MyCustomEFContextProvider _contextProvider = new MyCustomEFContextProvider();
...
[HttpPost]
public CustomSaveResult SaveChanges(JObject saveBundle) {
return _contextProvider.SaveChanges(saveBundle);
}
JSON.Net will happily serialize the usual material + your custom ErrorEntities property (be sure to make it serializable!) and send it to the Breeze client.
On the Breeze client you write your own variation on the stock Breeze Web API data service adapter. Yours does almost exactly the same thing as the Breeze version. But, when processing the save payload from the server, it also extracts this extra "error entities" material in the response and does whatever you want to do with it.
I don't know what that will be but now you have it.
See how easy that was? LOL.
Breeze does not currently support a save mechanism that both saves and returns an error at the same time. While possible this seems a bit baroque.
As you pointed out, you can
1) Throw an exception inside of the BeforeSaveEntities and fail the save. You can even specify which specific entity or entities caused the failure and why. In this case the entire save is aborted.
or
2) Remove 'bad' items from the saveMap within the BeforeSaveEntities and save only a subset of what was passed in. In this case you are performing a partial save.
But we don't support a hybrid of these two. Please add this to the Breeze User Voice if you feel strongly and we can see if other members of the community feel that this would be useful.