fix: extract path parameters correctly when the router is mounted as subrouter - #134
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pk-work merged 2 commits intoAug 10, 2026
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…subrouter The position of a path parameter was calculated from the beginning of the OpenAPI path template and applied to the path of the incoming request. When the router built from the contract is mounted as a subrouter, the request path contains additional leading segments, so the calculated position pointed to the wrong segment and validation failed or, even worse, validated the wrong value. Since mounting a router can only prepend segments to the request path, the number of additional leading segments is now determined by comparing the number of segments of the request path with the number of segments of the path template, and the parameter position is shifted accordingly. For routers that are not mounted as subrouter the behaviour is unchanged. Fixes eclipse-vertx#120
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Motivation
As reported in #120:
RequestUtilscalculates the position of a path parameter from the beginning of the OpenAPI path template (/entities/{id}→ segment 2) and applies it to the path of the incoming request. When the router built from the contract is mounted as a subrouter (e.g.mainRouter.route("/my-service/*").subRouter(router)), the request path (/my-service/entities/5) contains additional leading segments, so the calculated position points to the wrong segment. Validation then either fails with a confusing type error or — worse — silently validates the wrong value (forstringparameters).Changes
Mounting a router can only prepend segments to the request path, so the number of additional leading segments can be determined by comparing the segment count of the request path with the segment count of the path template. The parameter position is now shifted by this mount offset:
0and the behaviour is unchanged — including the existing handling of empty path parameters.Parameterargument ofextractPathParametersthat was mentioned in the issue discussion.One limitation worth being transparent about: a mounted router receiving an empty trailing path parameter (
/my-service/test/) remains ambiguous, because without knowing the mount point the extra segments cannot be distinguished from the parameter itself. Resolving that fully would require the mount information fromvertx-web(see vert-x3/vertx-web#2694). This change fixes the practically relevant cases without any API change.Fixes #120