Querying from custom table

Sorry but I am new to this, so I’m a little confused. I am currently trying to extend this plugin to return me data from a non WordPress table. I have created a new class file in lib, referring to the class-wp-json-posts.php as an example. So far, I’ve modified the register_routes function to take in the url that I want.

public function register_routes( $routes ) {
		$customer_routes = array(

			'/customers' => array (
				array( array ( $this, 'get_customers' ) ,
				WP_JSON_Server::READABLE ),
			),

		);
		return array_merge( $routes, $customer_routes );
	}

I know that I am supposed to create a customizes get_customers function to query the table that I want. But when I tested it out using the curl -i command, it gives me back “json_no_route”. What am I doing wrong? Or am I missing a step somewhere? Also, how to I accept parameters for my api call? For example: I want to have the url as http://example.com/wp-json/customers?param1=1&param2=2 ?

Thanks.

https://ww.wp.xz.cn/plugins/json-rest-api/