Asp.Net-Core + MongoDb - How to search database by "code" and return the original url? - mongodb

Question

I am unsure how to go about searching for the "Code" stored in my Database in order to return the "OriginalUrl".
I know I can search for the ObjectId but I want to be able to search by the "Code" assigned to that ObjectId.
Currently I have a working program that takes a Url as well as a "title" and sends it to the database:
It is assigned an Objectid _id and a randomly generated 12 character "Code":
If it helps this is my Controller class:
namespace ShortenUrls.Controllers
{
[Route("api/codes")]
public class ShortUrlsController : Controller
{
private readonly ShortUrlRepository _repo;
public ShortUrlsController(ShortUrlRepository repo)
{
_repo = repo;
}
[HttpGet("{id}")]
public async Task<IActionResult> Get(string id)
{
var su = await _repo.GetAsync(id);
if (su == null)
return NotFound();
return Ok(su);
}
[HttpPost]
public async Task<IActionResult> Create([FromBody] ShortUrl su)
{
await _repo.CreateAsync(su);
return Ok(su);
}
}
And Repository class:
namespace ShortenUrls.Models.Repository
{
public class ShortUrlRepository
{
private const string alphabet = "23456789bcdfghjkmnpqrstvwxyz-_";
private static readonly Random rand = new Random();
private readonly Database _db;
public ShortUrlRepository(Database db)
{
_db = db;
}
private static string GenerateCode()
{
const int codeLength = 12;
var chars = new char[codeLength];
for (var i = 0; i < codeLength; i++)
{
chars[i] = alphabet[rand.Next(0, alphabet.Length)];
}
return new string(chars);
}
public Task<ShortUrl> GetAsync(string id)
{
var objId = ObjectId.Parse(id);
return _db.Urls.Find(x => x.Id == objId).FirstOrDefaultAsync();
}
public Task CreateAsync(ShortUrl su)
{
su.Code = GenerateCode();
return _db.Urls.InsertOneAsync(su);
}
}

Answer 1

Just use a filter. Doing it this way let's you create a query specifically for the "code".
public async Task<ShortUrl> GetAsync(string code)
{
var filterBuilder = new FilterDefinitionBuilder<ShortUrl>();
var filter = filterBuilder.Eq(s => s.Code, code);
var cursor = await _db.Urls.FindAsync(filter);
return await cursor.FirstOrDefaultAsync();
}

Answer 2

Assuming you already know the code when calling this and that ObjectId is created on InsertOneAsync call. First change your repository to take Code as searchable input.
public Task<ShortUrl> GetAsync(string code)
{
return await _db.Urls.FirstOrDefaultAsync(x => x.Code == code);
}
Then change your controller Get to this:
[HttpGet("{code}")]
public async Task<IActionResult> Get(string code)
{
var su = await _repo.GetAsync(code);
if (su == null)
return NotFound();
return Ok(su);
}
In your controller you can access su.OriginalUrl if you need to only return that after getting the object.
Then in postman you can just call http://localhost:51767/api/codes?code=cmg3fjjr_gtv
Remember only Id works for default url parameters as setup by your default routes in Startup.cs.
app.UseMvc(routes => { /*...*/ })
So this wont work: /api/codes/cmg3fjjr_gtv unless you specifically set up routing or change {code} back to {id}. Readability of your code suffers though.