Question: which layer to implement audit fields

[fdlane]

Description

Currently I am implementing audit fields in the service layer. However, the values are only persisted to the db if the api user includes the properties in the request.

entity.EditedBy = _currentUser.Username; is not applied if the user does not include the property in the Patch request.

How do I get the audit fields to always be persisted?

public BaseService(
  IJsonApiContext jsonApiContext,
  IEntityRepository<T, Guid> repository,
  ILoggerFactory loggerFactory,
  ICurrentUser currentUser) : base(jsonApiContext, repository, loggerFactory)
{
  _currentUser = currentUser;
}

public override async Task<T> CreateAsync(T entity)
{
  entity.CreatedBy = _currentUser.Username;
  var newEntity = await base.CreateAsync(entity);
  return newEntity;
}

public override async Task<T> UpdateAsync(Guid id, T entity)
{
  entity.EditedBy = _currentUser.Username;
  entity.EditedDate = DateTime.Now;

  var updatedEntity = await base.UpdateAsync(id, entity);

  return updatedEntity;
}

Environment

• JsonApiDotNetCore Version: v4.0.0-alpha3

[maurei]

Hi @fdlane, this indeed is a bit less easy than one would expect. Internally the repository accesses a list of all targeted attributes to know which ones to update:

JsonApiDotNetCore/src/JsonApiDotNetCore/Data/DefaultResourceRepository.cs

Line 190 in 1ac9d9c

foreach (var attribute in _targetedFields.Attributes)

That means AttrAttribute instances associated to your EditedBy and EditedDate field must be in that list. Indeed, this is taken care of under the hood when an attribute is targeted through a PATCH request. In your case you would have to add this attribute to the list manually.

In v4.0.0-alpha4 this is relatively straight forward using the ITargetedFields and IResourceGraphExplorer services:

public BaseService(
  ... ,
  ITargetedFields targetedFields,
  IResourceGraphExplorer graph,
  ...) : base( ... ) { ... }

public override async Task<T> UpdateAsync(Guid id, T entity)
{
  entity.EditedBy = _currentUser.Username;
  entity.EditedDate = DateTime.Now;

  var attributes = _graph.GetAttributes<YourResource>( r => new { r.EditedBy, r.EditedDate });
  _targetedFields.AddRange(attributes);

  var updatedEntity = await base.UpdateAsync(id, entity);

  return updatedEntity;
}

I see you're on alpha3 though. There, the equivalent of ITargetedFields is the AttributesToUpdate property on IJsonApiContext:

JsonApiDotNetCore/src/JsonApiDotNetCore/Data/DefaultEntityRepository.cs

Line 271 in ec4e76e

foreach (var attr in _jsonApiContext.AttributesToUpdate.Keys)

To get a hold of the attributes see my post here #536 (comment). That is still a bit complicated in alpha3. I would recommend you to switch to alpha4 ASAP anyway.

Let me know if that helps!

[fdlane]

This was a great help and we will be moving to alpha4 soon. Thank you!

My base class based on #536

  public class BaseService<T> : EntityResourceService<T, Guid> where T : BaseEntity
    {
      private readonly ICurrentUser _currentUser;
      private readonly IResourceGraph _resourceGraph;
      private readonly IJsonApiContext _jsonApiContext;

      public BaseService(
        IJsonApiContext jsonApiContext,
        IEntityRepository<T, Guid> repository,
        ILoggerFactory loggerFactory,
        IResourceGraph resourceGraph,
        ICurrentUser currentUser) : base(jsonApiContext, repository, loggerFactory)
      {
        _currentUser = currentUser;
        _resourceGraph = resourceGraph;
        _jsonApiContext = jsonApiContext;
      }

      public override async Task<T> CreateAsync(T entity)
      {
        entity.CreatedBy = _currentUser.Username;
        var newEntity = await base.CreateAsync(entity);
        return newEntity;
      }

      public override async Task<T> UpdateAsync(Guid id, T entity)
      {
        entity.EditedBy = _currentUser.Username;
        entity.EditedDate = DateTime.Now;

        var editedByAttribute = _resourceGraph.GetContextEntity(typeof(T)).Attributes.Single(a => a.InternalAttributeName == "EditedBy");
        _jsonApiContext.AttributesToUpdate.Add(editedByAttribute, editedByAttribute);

        var editedDateAttribute = _resourceGraph.GetContextEntity(typeof(T)).Attributes.Single(a => a.InternalAttributeName == "EditedDate");
        _jsonApiContext.AttributesToUpdate.Add(editedDateAttribute, editedDateAttribute);

        var updatedEntity = await base.UpdateAsync(id, entity);

        return updatedEntity;
      }
    }

[fdlane]

Thanks for the help.