Add (Request)ParameterHandlerMapping class to Spring MVC [SPR-2309]

[spring-projects-issues]

Glen Mazza opened SPR-2309 and commented

I have found the RequestParameterHandlerMapping class, defined on p. 92-93 of APress' Expert Spring MVC and Web Flow book, to be very useful for my work. I'm inclined to recommend adding a class like this one to the Spring 2.0 Core. (Spring already has a very similar ParameterHandlerMapping[1] in 2.0, but that is only for portlets, not Spring MVC.)

Here is my use case for it: I have a report generation system that uses a "report" parameter to determine which report to generate:
https://www.mycompany.com/ReportGen/login?report=ReportA
https://www.mycompany.com/ReportGen/login?report=ReportB
https://www.mycompany.com/ReportGen/login?report=ReportC
...

Previously, I mapped the "login" URL via SimpleURLHandlerMapping to a (SimpleFormController subclass) loginController, which internally did hardcoded validation to make sure that the report parameter was valid (e.g., raise an exception if report=doesntexist, but for valid report param values redirect after login to a report-specific controller to collect the report's filtering criteria.) This however, required me to keep modifying my loginController class everytime a report was added or removed.

But by using RequestParameterHandlerMapping I can now map the parameters ReportA, ReportB, ReportC, etc., individually to loginController in my web config file. With this design, report=doesntexist will never activate loginController to begin with so I can just return an error page in that case. It seems like a cleaner design.

Thanks,
Glen

[1] http://static.springframework.org/spring/docs/2.0.x/api/org/springframework/web/portlet/handler/ParameterHandlerMapping.html

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Affects: 2.0 RC3

[spring-projects-issues]

Glen Mazza commented

Actually, this may not be a good idea after all, at least as-is. The problem with allowing RequestParameterHandlerMapping, is that while:

https://www.mycompany.com/ReportGen/login.do?report=ReportA
https://www.mycompany.com/ReportGen/login.do?report=ReportB
https://www.mycompany.com/ReportGen/login.do?report=ReportC

will all nicely resolve correctly, so will:

https://www.mycompany.com/ReportGen/lsdfas.do?report=ReportA
https://www.mycompany.com/ReportGen/dfhsfdgh.do?report=ReportB
https://www.mycompany.com/ReportGen/sdgbsfd.do?report=ReportC

which doesn't seem to be such a good idea.

Glen

[spring-projects-issues]

Glen Mazza commented

Then again, I just fixed the problem above by adding a new "requiredServletPath" property to the RequestParameterHandlerMapping, and by setting it to "/login.do" in my configuration file. Then, changing the RPHM.getHandlerInternal() to:

protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
    if (requiredServletPath == null || requiredServletPath.equals(request.getServletPath())) {       
        String parameterValue = request.getParameter(parameterName);
        return paramMappings.get(parameterValue);
    } else {
        return null;
    }
}

I guess I'm neutral now on its inclusion into Spring, but absent other votes for it I suspect it should be left out.

Glen

[spring-projects-issues]

Rossen Stoyanchev commented

I think this can be considered resolved with @RequestMapping annotations that can be used to map by URL path and request parameters.