#2775: `PageParameterAwareMountedMapper.java`

projectforge-wicket/src/main/java/de/micromata/wicket/request/mapper/PageParameterAwareMountedMapper.java Wicket Request Mapper (URL Routing) · projectforge-wicket/src/main/java/de/micromata/wicket/request/mapper/PageParameterAwareMountedMapper.java 126 lines · 47 code · 71 comments · 8 blank

A critical Wicket URL routing fix that addresses a subtle defect in Wicket's default MountedMapper behavior. When a user manually edits a Wicket URL — for example changing /User/4?15 to /User/5?15 — the default mapper prioritizes the page ID query parameter (?15) over the path parameters (/5), causing the user to see the cached page for user 4 instead of a fresh page for user 5. This custom mapper detects mismatches between the cached page's parameters and the current request's parameters, and redirects to a fresh bookmarkable page instance when they differ, ensuring the URL always reflects the actual displayed content.

Architecture

Override Strategy

The class extends MountedMapper and overrides only processHybrid() — the method Wicket calls when it has both a page ID (from a session-cached page) and path parameters (from the URL). The override:

Calls the parent processHybrid() to get the default handler
Catches PageExpiredException — if the cached page has expired, falls back to processBookmarkable() which creates a fresh page
If the parent returned a RenderPageRequestHandler with a PageProvider that has a page instance, compares: (a) the page class of the cached instance vs. the requested page class, and (b) the cached page parameters vs. the current request parameters
If either comparison fails, redirects to processBookmarkable() — a fresh, stateless page instance with the correct parameters

The Root Problem

Wicket's MountedMapper implements a "hybrid" strategy: if a page ID exists in the URL (either as ?wicket:pageId=15 or via ?15 shorthand), load the serialized page from the page store; otherwise create a fresh bookmarkable instance. The problem is that once a session has a cached page (say page ID 15 for user 4), subsequent requests with different path parameters but the same page ID will serve the cached page — the mapper never compares the path parameters against the cached page's parameters. URL manipulation by users (or browser history) would display stale data.

Mounting Usage

Pages are mounted in WicketApplication.init() using mount(new PageParameterAwareMountedMapper("Home", HomePage.class)) instead of mountPage(). This is documented in the class's own Javadoc with a usage example.

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