⚙️ Request Handler

In this section, we illustrate the powerful concept of RequestHandler in Flash, which are used to handle incoming requests and generate responses.

Creating a Request Handler

To create a custom request handler, you need to extend the RequestHandler class and annotate the class with the RouteInfo annotation, specifying the HTTP method that the handler will respond to and the relative path that the handler will be registered to. The enforceNonNullBody attribute is used to specify whether the handler expects a non-null request body: by default, it is set to false. After that, you must override the handle method; The handle method is where you define the logic for processing the request and generating the response. The req (request) and res (response) objects are available in the handler to access the request data and send the response back to the client.

You must call the super constructor with the req and res objects to initialize the handler.

import flash.Request;
import flash.Response;
import flash.RequestHandler;

@RouteInfo(method = HttpMethod.GET, path = "/hello", enforceNonNullBody = false)
public class MyHandler extends RequestHandler {
    public MyHandler(Request req, Response res) {
        super(req, res);
    }

    @Override
    public Object handle() {
        String response = "Hello, world!";
        return response;
    }
}

WARNING

Any logic that needs to be executed before the request handler is registered must be done within the constructor.

Request Handler methods

The RequestHandler class provides several methods that can be used to interact with the request and response objects easily and safely. Following are listed the methods available in the RequestHandler class, with a brief description of their purpose:

Method	Params	Description
getRequestBody()	none	Returns a JSONObject representation of the request body.
getSpecification()	none	Returns an instance of HandlerSpecification containing all sorts of information about the handler.
expectedRequestParameter()	String name, description	Returns an instance of ExpectedRequestParameter for the specified parameter name.
expectedBodyField()	String name, description	Returns an instance of ExpectedBodyField for the specified field name.
expectedBodyFile()	String name, description	Returns an instance of ExpectedBodyFile for the specified file name.

(More on the ExpectedRequestParameter, ExpectedBodyField, and ExpectedBodyFile classes in the next section).