The AddTaskRequestValidator is responsible for making sure the api request is valid. If it is not it will trigger a http response with status code 400 and an error message indicating which part of the input was invalid.
public sealed class AddTaskRequestValidator : AbstractValidator<AddTaskRequest>
{
public AddTaskRequestValidator()
{
RuleFor(task => task.TaskId)
.MinimumLength(1)
.NotEmpty();
RuleFor(task => task.Title)
.MinimumLength(3)
.MaximumLength(50)
.NotEmpty();
RuleFor(task => task.Description)
.MaximumLength(150);
//Due Date Can't Be in the Past
RuleFor(task => task.DueDate)
.GreaterThan(DateTime.Today.AddDays(-1));
}
}The AddTaskController in this example is at the application layer it is the public facing interface to the application. Note:Controllers usually only contain a single action
[ApiController]
[Route("api/Tasks/Add")]
public sealed class AddTaskController : ControllerBase
{
private readonly IQueryProcessor _queryProcessor;
private readonly IAmACommandProcessor _commandProcessor;
private readonly ILogger<AddTaskController> _logger;
public AddTaskController(
IQueryProcessor queryProcessor,
IAmACommandProcessor commandProcessor,
ILogger<AddTaskController> logger)
{
_queryProcessor = queryProcessor;
_commandProcessor = commandProcessor;
_logger = logger;
}
[HttpPost]
public async Task<IActionResult> AddTask(AddTaskRequest request)
{
//This is sharing the GetTaskQuery which is a trade off to querying this in the AddTaskCommand.
var task = await _queryProcessor.ExecuteAsync(new GetTaskQuery(request.TaskId));
if(task != null)
{
return BadRequest($"Task with TaskId {request.TaskId} already exists");
}
await _commandProcessor.SendAsync(new AddTaskCommand(request.TaskId, request.Title, request.Description,
request.DueDate));
var newUrl = $@"{Request.Host}/api/tasks/{request.TaskId}";
return Created(newUrl,
new AddTaskResponse(request.TaskId, request.Title, request.Description, request.DueDate));
}
}The application layer as in most n-tier architecture depends on a domain or business layer.
In the Slice application I'm using the AddTaskCommand as a domain layer component in this workflow. It's job is to accept the appropriate inputs needed to create a task.
public sealed class AddTaskCommand : Command
{
public string TaskId { get; }
public string Title { get; }
public string Description { get; }
public DateTime? DueDate { get; }
public AddTaskCommand(string taskId, string title, string description, DateTime? dueDate) : base(new Guid())
{
TaskId = taskId;
Title = title;
Description = description;
DueDate = dueDate;
}
}In this example the AddTaskCommandHandler plays a part in the business layer and the data layer. It's responsible for validating the command (not done here.) and storing the new task in the database. If there is a failure in either part it will throw an exception back to the caller.
public sealed class AddTaskCommandHandlerAsync : RequestHandlerAsync<AddTaskCommand>
{
private readonly string _connectionString;
public AddTaskCommandHandlerAsync(IConnectionString connectionString)
{
_connectionString = connectionString.ConnectionString;
}
[UsePolicyAsync(CommandProcessor.RETRYPOLICYASYNC, 1)]
public override async Task<AddTaskCommand> HandleAsync(AddTaskCommand command, CancellationToken cancellationToken = default)
{
var addTaskQuery = @"INSERT INTO TASKS (TaskId,Title, Description,DueDate)VALUES(@TaskId, @Title,@Description, @DueDate);";
await using (var sqlConnection = new SqlConnection(_connectionString))
{
await sqlConnection.ExecuteAsync(new CommandDefinition(addTaskQuery, command,
cancellationToken: cancellationToken));
}
return await base.HandleAsync(command, cancellationToken);
}
}