I'm using ASP.Net WebAPI. What I'm trying to achieve is to gathers all Request in a List<T>, and sent it by bulk to somewhere else. Basically my requirement is to sent it by bulk only when the list reaches some number or some period of time.
Since List<T> is not a thread safe, so I assume I must use ConcurrentBag<T>. But how do I get the instance of previous created Bag?
public class MyController : ApiController
{
private IList<object> _requests;
public MyController(){
_requests = new List<object>();
}
public void Post()
{
if (_requests.Count < SomeCounter)
_requests.Add(Request);
else
...Send Bulk..
}
}
Related
I have two versions of an API.
The second version of API will be having only one action method instead of two action methods in first version of API.
Second version of API action method will basically combine responses of first version of API's both action methods and return combined response to client.
Example code as follows:
[ApiController]
[Route("[controller]")]
public class NumbersV1Controller : ControllerBase
{
private readonly ILogger<NumbersV1Controller> _logger;
public NumbersV1Controller(ILogger<NumbersV1Controller> logger)
{
_logger = logger;
}
[HttpGet]
public int Get()
{
return 1;
}
[HttpPost]
public int Post()
{
return 2;
}
}
[ApiController]
[Route("[controller]")]
public class NumbersV2Controller : ControllerBase
{
private readonly ILogger<NumbersV2Controller> _logger;
public NumbersV2Controller(ILogger<NumbersV2Controller> logger)
{
_logger = logger;
}
[HttpPost]
public IEnumerable<int> Get()
{
// Method 1: Make a direct HTTP request.
// int response1 = HTTPClientHelper.GetRequest("Get", "NumbersV1");
// int response2 = HTTPClientHelper.PostRequest("Post", "NumbersV1");
// Method 2: Use instances and set controller context.
NumbersV1Controller numbersV1Controller = new NumbersV1Controller(null);
numbersV1Controller.ControllerContext = this.ControllerContext;
int response1 = numbersV1Controller.Get();
int response2 = numbersV1Controller.Post();
// Method 3: Use RedirectToAction method.
// RedirectToActionResult response1 = RedirectToAction("Get", "NumbersV1");
// RedirectToActionResult response2 = RedirectToAction("Post", "NumbersV1");
return new List<int>() { response1, response2 };
}
}
Method 1: Make a direct HTTP request.
It works perfectly but it is having additional boilerplate code and also it like making a new network call.
Method 2: Use instances and set controller context.
Not sure if this will work perfectly like can I access the Request object in version 1 controller and not sure how to initialize the version 2 controller will multiple injected objects
Method 3: Use RedirectToAction method.
I was assuming RedirectToAction will work but I don't see the result of the Action method in response object RedirectToActionResult.
What are the best options available for doing this in .NET Web API or is there any other way of doing this elegently?
Avoid using method 2 / method 3. Why? It violates so many patterns and performance will be an issue.
Method 1 is average if you really want to do it that way but will cost a network call though.
Method 4:
You can call directly inline business logic code from your V2 controller. If you already separated your business logic code to an individual service then you need to call it from your controller.
I have introduced a new class to do all the logical operations. You might have a similar one / many service classes for handling business requirements.
Let me give you an example:
public class Number1Controller : BaseController {
// You can use DI container to resolve this. I am using this as an example.
private readonly Service _service = new();
[HttpGet("{id}")]
public int GetById(int id) => _service.GetById(id);
[HttpGet("{name}")]
public string GetByName(string name) => _service.GetByName(name);
}
public class Number2Controller : BaseController {
// You can use DI container to resolve this. I am using this as an example.
private readonly Service _service = new();
[HttpGet("{id}")]
public int GetById(int id) => _service.GetById(id);
[HttpGet("{name}")]
public string GetByName(string name) => _service.GetByName(name);
}
// Business Logic Service
public class Service {
public int GetById(int id) => 1;
public string GetByName(string name) => "Stack Over Flow";
}
I'm implementing Spring Boot App which reads some data from kafka to provide it for all requesting clients. Let's say I have a following class:
#Component
public class DataProvider {
private Prices prices;
public DataProvider() {
this.prices = Prices.of();
}
public Prices getPrices() {
return prices;
}
}
Each client may perform GET /api/prices to get info about newest prices. Live updates about prices are consumed from kafka. Due to the fact, that update comes every 5 seconds, which is not super often, the topic has only one partition.
I tried the very basic option using Kafka Listener:
#Component
public class DataProvider {
private Prices prices;
public DataProvider() {
this.prices = Prices.of();
}
public Prices getPrices() {
return prices;
}
#KafkaListener(topics = "test-topic")
public void consume(String message) {
Prices prices = Prices.of(message);
this.prices = prices;
}
}
Is this approach safe?
The prices must be volatile. But again: you need to be sure that an actual data for prices is OK to be dispersed. One HTTP request may return one data, but another concurrent may return other. Just because it has been just update by the Kafka consumer.
You may have your consume() and getPrices() as synchronized. So, every one is going to get an actual data at the same moment. However they are not going to be parallel since synchronized ensures only one thread can get access to the object.
Another way for consistency is to look into a ReadWriteLock barrier. So, getPrices() calls can be parallel, but as long as consume() takes a WriteLock, everyone is blocked until it is done.
So, technically your code is really safe. Only the problem if it is safe from a business purpose.
The client periodically calls an async method (long polling), passing it a value of a stock symbol, which the server uses to query the database and return the object back to the client.
I am using Spring's DeferredResult class, however I'm not familiar with how it works. Notice how I am using the symbol property (sent from client) to query the database for new data (see below).
Perhaps there is a better approach for long polling with Spring?
How do I pass the symbol property from the method deferredResult() to processQueues()?
private final Queue<DeferredResult<String>> responseBodyQueue = new ConcurrentLinkedQueue<>();
#RequestMapping("/poll/{symbol}")
public #ResponseBody DeferredResult<String> deferredResult(#PathVariable("symbol") String symbol) {
DeferredResult<String> result = new DeferredResult<String>();
this.responseBodyQueue.add(result);
return result;
}
#Scheduled(fixedRate=2000)
public void processQueues() {
for (DeferredResult<String> result : this.responseBodyQueue) {
Quote quote = jpaStockQuoteRepository.findStock(symbol);
result.setResult(quote);
this.responseBodyQueue.remove(result);
}
}
DeferredResult in Spring 4.1.7:
Subclasses can extend this class to easily associate additional data or behavior with the DeferredResult. For example, one might want to associate the user used to create the DeferredResult by extending the class and adding an additional property for the user. In this way, the user could easily be accessed later without the need to use a data structure to do the mapping.
You can extend DeferredResult and save the symbol parameter as a class field.
static class DeferredQuote extends DeferredResult<Quote> {
private final String symbol;
public DeferredQuote(String symbol) {
this.symbol = symbol;
}
}
#RequestMapping("/poll/{symbol}")
public #ResponseBody DeferredQuote deferredResult(#PathVariable("symbol") String symbol) {
DeferredQuote result = new DeferredQuote(symbol);
responseBodyQueue.add(result);
return result;
}
#Scheduled(fixedRate = 2000)
public void processQueues() {
for (DeferredQuote result : responseBodyQueue) {
Quote quote = jpaStockQuoteRepository.findStock(result.symbol);
result.setResult(quote);
responseBodyQueue.remove(result);
}
}
I have just implemented output caching of my Asp.Net Web API Controllers using StrathWeb's library connecting to the StackExchange.Redis library connecting through to an Azure-hosted Redis Cache.
I have written a custom class that implements the StrathWeb IApiOutputCache interface and calls the equivalent StackExchange methods. This is registered as the cache output provder in Global.asax.cs.
Here's an example of usage:
public class MyApiController : ApiController
{
private const int FIFTEEN_MINUTES_IN_SECONDS = 900;
[CacheOutput(ClientTimeSpan = FIFTEEN_MINUTES_IN_SECONDS, ServerTimeSpan = FIFTEEN_MINUTES_IN_SECONDS)]
async public Task<Data> GetAsync(int param1, string param2)
{
return await GetExpensiveData();
}
[Serializable]
public class Data
{
// Members omitted for brevity
}
}
When a call is made to the api endpoint I can see that the framework correctly calls all the required methods on my IApiOutputCache class: Contains, Set and Get. However, even when a cached copy is found and returned, the GetExpensiveData() method is always run and the 'fresh' data returned.
No errors are thrown. The cache seems to be working. Yet, my expensive code is always called.
Thanks for your help :).
Problem solved. I was incorrectly calling into Redis from my IApiOutputCache class.
Before...
public class AzureRedisApiOutputCache : IApiOutputCache
{
public object Get(string key)
{
return AzureRedisCache.Instance.GetDatabase().StringGet(key);
}
}
After...
public class AzureRedisApiOutputCache : IApiOutputCache
{
public object Get(string key)
{
// Call the extension method that also performs deserialization...
return AzureRedisCache.Instance.GetDatabase().Get(key);
}
}
public static class RedisDatabaseExtensions
{
public static object Get(this IDatabase cache, string key)
{
return Deserialize<object>(cache.StringGet(key));
}
}
This confused me for some time as the CacheOutput framework never reported an error. It just silently failed and fell back to the controller method.
I have an app with an AngularJS front-end and a Spring MVC back-end. I'm having some trouble with converting/mapping request objects to domain/dto objects.
On one page you can add a new order to the system, the POST payload would look something like this:
{
memo: "This is some extra info for order",
orderLines: [{productId:3, quantity:4}, {productId:2, quantity:5}, {productId:1, quantity:4}],
shippingDate: "2014-10-08T19:16:19.947Z",
warehouseId: 2
}
The Spring MVC controller method looks like this:
#RequestMapping(value = "/order", method = RequestMethod.POST)
public ResponseEntity<Void> addOrder(#RequestBody #Valid OrderRequest orderRequest, UriComponentsBuilder b) throws Exception {
// the magic
}
Where OrderRequest is filled with the values of the POST request, the OrderRequest and OrderLineRequest look like this:
public class OrderRequest {
private Long id;
private Date shippingDate;
private String memo;
private List<OrderLineRequest> orderLines;
private Long warehouseId;
public OrderRequest() {
}
// getters and setters ommitted
}
public class OrderLineRequest {
private Long id;
private String productCode;
private int quantity;
public OrderLineRequest() {
}
}
My question now is, in order to save an Order object with orderService.add(order) I need to construct the Order object based on the values that were sent in the request. Where/how do I do this?
OPTION 1
The OrderRequest class could have a makeOrder() method with just returns an Order object like so:
public Order makeOrder() {
Order order = new Order();
order.setMemo(this.memo);
order.setShippingDate(this.shippingDate);
...
}
Then I'd have to map the OrderLineRequest which could have their own makeOrderLine method:
public OrderLine makeOrderLine() {
OrderLine orderLine = new OrderLine();
orderLine.setQuantity = this.quantity;
...what to do with only the productId?
}
As you can see I can set the quantity but in the request I only received the productId, but in the database I save the productCode, productName as well, so I need that info from the database, but I don't want to make a database call from the Request object...I also don't want to half of the mapping in the request object and the rest of the mapping in the controller where I do have access to the services.
OPTION 2
I can use Dozer to do the mapping for me, but that would mean injecting the services into the Dozer custom converters which seem equally unclean to me...
OPTION 3
I pass the OrderRequest object to the service layer and let the service layer handle it, but my question would remain, how exactly would the service layer convert it, say you have the method addOrder like this:
public void addOrder(OrderRequest orderRequest) {
}
Would you call another service to convert from one to the other as I don't really want this conversion in a business logic method?
Any help would be appreciated
use the #RequestBody to map your jsonObject that is send with the request , to a DTO .
please refer to the following tutorial .
hope that helps .
and please ask if there is something not clear .