New RAD Server Features in RAD Studio 10.3

The version of RAD Server that ships with RAD Studio 10.3 offers a very significant set of enhancements, mostly focused on how a resource (and have a URL) is mapped to classes and methods on the server. While the key idea of having classes (or data modules) that implement resources remains the same, there are two new approaches:

• First, you can now map the same URL and HTTP Verb to multiple method handlers, based on content type and accept types HTTP headers. As a side change, you can also freely map HTTP verbs to custom methods names.
• Second, rather then implementing the actual methods for the HTTP verbs in the resource class, they can be forwarded to a separate and possibly shared implementation class, which needs to support a specific interface. To further simplify things, RAD Studio includes ready to use components for files and datasets management

In this blog post I don’t want to cover all of the options, but just guide you through same example I wrote for my CodeRage 2018 session on RAD Server – the entire source code is also available on GitHub at https://github.com/marcocantu/DelphiSessions/tree/master/RADServer103CodeRage.

Using Multiple Accept Types with EndpointProduce

One of the new features I mentioned above is the ability to have the same exact URL mapped to different methods depending on some HTTP headers. For a GET operation, you can discriminate on the content type indicated in the Accept HTTP header. You do so by decorating the methods with the EndpointProduce attribute plus a related MIME type.

This is the example of a class accepting either images or general data (for Chrome at least application/xml is in any general call):

The implementation of these methods is rather trivial, as all the code does is return a file:

How can you test it? Certainly not just pointing your browser to the URL – if you do you invariably receive the result of the second method, but you might also get an error message indicating that none of the available endpoints matches the request. For a simple test, I wrote the following HTML code, which refers to the same URL in two different ways the browser resolves with different Accept headers in the request: