src/main/java/io/netty/handler/codec/http/router/OrderlessRouter.java
public OrderlessRouter<T> addRoute(String pathPattern, T target) {
        PathPattern p = new PathPattern(pathPattern);
        if (routes.containsKey(p)) {
            return this;
        }

        routes.put(p, target);
        addReverseRoute(target, p);
        return this;
    }
public OrderlessRouter<T> addRoute(String pathPattern, T target) {
        PathPattern p = new PathPattern(pathPattern);
        if (routes.containsKey(p)) {
            return this;
        }

        routes.put(p, target);
        addReverseRoute(target, p);
        return this;
    }
This method does nothing if the path pattern has already been added.
A path pattern can only point to one target.