I think this is what you need
https://ocelot.readthedocs.io/en/latest/features/delegatinghandlers.html
I have not checked that you change the http verbs etc but I would guess you can along with adding querystring params to the onward request (you will have the http request message). I think you should be able to do almost anything you like!
Here is an untested example of the type of code you could implement
public class PostToGetHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
// Only want to do this if it matches our route
// See section later on about global or route specific handlers
if (request.RequestUri.OriginalString.Contains("/mobile/ImageService.svc/json/GetImage") && request.Method.Equals(HttpMethod.Post))
{
var bodyString = await request.Content.ReadAsStringAsync();
// Deserialize into a MyClass that will hold your request body data
var myClass = JsonConvert.DeserializeObject<MyClass>(bodyString);
// Append your querystrings
var builder = new QueryBuilder();
builder.Add("ImageId", myClass.ImageId);
builder.Add("MaxWidth", myClass.MaxWidth); // Keep adding queryString values
// Build a new uri with the querystrings
var uriBuilder = new UriBuilder(request.RequestUri);
uriBuilder.Query = builder.ToQueryString().Value;
// TODO - Check if querystring already exists etc
request.RequestUri = uriBuilder.Uri;
// Add your header - TODO - Check to see if this header already exists
request.Headers.Add("SessionId", myClass.SessionId.ToString());
// Get rid of the POST content
request.Content = null;
}
// On it goes either amended or not
// Assumes Ocelot will change the verb to a GET as part of its transformation
return await base.SendAsync(request, cancellationToken);
}
}
It can be registered like this in the Ocelot startup
services.AddDelegatingHandler<PostToGetHandler>();
or
services.AddDelegatingHandler<PostToGetHandler>(true); // Make it global
These handlers can be global or route specific (so you may not need the route check in the code above if you make it route specific)
This is from the Ocelot docs:
Finally if you want ReRoute specific DelegatingHandlers or to order
your specific and / or global (more on this later) DelegatingHandlers
then you must add the following json to the specific ReRoute in
ocelot.json. The names in the array must match the class names of your
DelegatingHandlers for Ocelot to match them together.
"DelegatingHandlers": [
"PostToGetHandler"
]
I would suggest initially adding a simple handler to your Ocelot instance and testing and adding to it to get it to do what you want. Ihope this helps with what you want to do.
