Routes can contain static parts and variable parts called route parameters. This section explains how to define and access path parameters.

The basic syntax for route parameters is the parameter name in curly braces so an example would be /profiles/{username}. You can have as many route parameters as you want and they can be in any place. To allow more specific parameters and automatic mapping into java types you can optionally specify a type by adding the type's name followed by a colon in front of the parameter name so this would like /users/{i+:id} for example. Unless specified it defaults to string.

To add your own parameters from scratch you can extend the abstract class RouteParamTransformer but i would recommend to extend the DefaultRouteParamTransformer as it already comes with predefined base types that you can build on using the extend method.

public enum QuizAnswer {
    A, B, C, D
}

public class CustomRouteParamTransformer extends DefaultRouteParamTransformer {

    public CustomRouteParamTransformer() {
        add("quizanswer|qa", "[A-D]", (e,s) -> QuizAnswer.valueOf((String) s)); // Create an new type from scratch
        extend("i+", "question", (e,s) -> Quiz.findQuestion((Integer) s)); // Extend an existing type
    }

}

To register your custom transformer you can use the method routeParamTransformer

server.routeParamTransformer(new CustomRouteParamTransformer());

To access the parameter values the Exchange currently exposes a Map<String, Object> Field pathVariables that contains all path variables. When using annotated controllers you can also annotate parameters with the @Path("variablename") annotation to inject the path parameter.

public class SomeController {

    @Get("/{param1}/{param2}")
    public void example(Exchange exchange, @Path("param1") String param1) {
        String param2 = (String) exchange.pathVariables.get("param2");
    }

}