| Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next

C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

C-ORM: docs, API.

Last 100 entries

History Books; Iraq + The (UK) Governing Elite; Answering Some Hard Questions; Pinochet: The Dictator's Shadow; An Outsider's Guide To Julia Packages; Nobody gives a shit; Lepton Decay Irregularity; An Easier Way; Julia's BinDeps (aka How To Install Cairo); Good Example Of Good Police Work (And Anonymity Being Hard); Best Santiago Burgers; Also; Michael Emmerich (Vibrator Translator) Interview (Japanese Books); Clarice Lispector (Brazillian Writer); Books On Evolution; Looks like Ara (Modular Phone) is dead; Index - Translations From Chile; More Emotion in Chilean Wines; Week 7; Aeon Magazine (Science-ish); QM, Deutsch, Constructor Theory; Interesting Talk Transcripts; Interesting Suggestion Of Election Fraud; "Hard" Books; Articles or Papers on depolarizing the US; Textbook for "QM as complex probabilities"; SFO Get Libor Trader (14 years); Why Are There Still So Many Jobs?; Navier Stokes Incomplete; More on Benford; FBI Claimed Vandalism; Architectural Tessellation; Also: Go, Blake's 7; Delusions of Gender (book); Crypto AG DID work with NSA / GCHQ; UNUMS (Universal Number Format); MOOCs (Massive Open Online Courses); Interesting Looking Game; Euler's Theorem for Polynomials; Weeks 3-6; Reddit Comment; Differential Cryptanalysis For Dummies; Japanese Graphic Design; Books To Be Re-Read; And Today I Learned Bugs Need Clear Examples; Factoring a 67 bit prime in your head; Islamic Geometric Art; Useful Julia Backtraces from Tasks; Nothing, however, is lost with less discomfort than that which, when lost, cannot be missed; Article on Didion; Cost of Living by City; British Slavery; Derrida on Metaphor; African SciFi; Traits in Julia; Alternative Japanese Lit; Pulic Key as Address (Snow); Why Information Grows; The Blindness Of The Chilean Elite; Some Victoriagate Links; This Is Why I Left StackOverflow; New TLS Implementation; Maths for Physicists; How I Am 8; 1000 Word Philosophy; Cyberpunk Reading List; Detailed Discussion of Message Dispatch in ParserCombinator Library for Julia; FizzBuzz in Julia w Dependent Types; kokko - Design Shop in Osaka; Summary of Greece, Currently; LLVM and GPUs; See Also; Schoolgirl Groyps (Maths); Japanese Lit; Another Example - Modular Arithmetic; Music from United; Python 2 and 3 compatible alternative.; Read Agatha Christie for the Plot; A Constructive Look at TempleOS; Music Thread w Many Recommendations; Fixed Version; A Useful Julia Macro To Define Equality And Hash; k3b cdrom access, OpenSuse 13.1; Week 2; From outside, the UK looks less than stellar; Huge Fonts in VirtualBox; Keen - Complex Emergencies; The Fallen of World War II; Some Spanish Fiction; Calling C From Fortran 95; Bjork DJ Set; Z3 Example With Python; Week 1; Useful Guide To Starting With IJulia; UK Election + Media; Review: Reinventing Organizations; Inline Assembly With Julia / LLVM; Against the definition of types; Dumb Crypto Paper; The Search For Quasi-Periodicity...; Is There An Alternative To Processing?

© 2006-2015 Andrew Cooke (site) / post authors (content).

Forcing lower case HTTP parameter names in Spring

From: andrew cooke <andrew@...>

Date: Sat, 7 Sep 2013 00:49:19 -0400

A client wanted (quite reasonably, imho) the case of REST parameters to be
unimportant.  Unfortunately Spring's RequestParam is case sensitive, and
rewriting the controllers to avoid that would be a fair amount of work.

So, instead, I found that a servlet filter should do the job.  And it works
nicely.

Andrew


In web.xml:

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>WEB-INF/dispatch-servlet.xml</param-value>
    </context-param>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <filter>
        <filter-name>delegatingFilter</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>delegatingFilter</filter-name>
        <url-pattern>*</url-pattern>
    </filter-mapping>


In dispatch-servlet.xml:

    <bean id="delegatingFilter"
          class="org.springframework.web.filter.DelegatingFilterProxy"
          p:targetBeanName="lowerParams"/>

    <bean id="lowerParams"
          class="com.isti.bss.mvc.LowerCaseParametersFilter"/>


And the code itself:

public final class LowerCaseParametersFilter implements Filter {

    private static final Logger LOG =
            Logger.getLogger(LowerCaseParametersFilter.class);

    @Override
    public void init(final FilterConfig filterConfig) throws ServletException
    {
    }

    @Override
    public void doFilter(final ServletRequest request,
                         final ServletResponse response,
                         final FilterChain chain)
            throws IOException, ServletException {
        if (request instanceof HttpServletRequest) {
            LOG.debug("Wrapping request");
            chain.doFilter(new LowerCaseRequest((HttpServletRequest) request),
                           response);
        } else {
            LOG.warn(format("Not wrapping request: %s", request.getClass()));
            chain.doFilter(request, response);
        }
    }

    @Override
    public void destroy() {
    }

    private static class LowerCaseRequest extends HttpServletRequestWrapper {

        private Map<String, String[]> lowerCaseParams = new HashMap<>();

        public LowerCaseRequest(final HttpServletRequest request) {
            super(request);
            Map<String, String[]> orignalParams = request.getParameterMap();
            for (String name: orignalParams.keySet()) {
                String lower = name.toLowerCase();
                if (!lowerCaseParams.containsKey(lower)) {
                    lowerCaseParams.put(lower, new String[0]);
                }
                lowerCaseParams.put(lower,
                        concat(lowerCaseParams.get(lower),
                                orignalParams.get(name),
                                String.class));
            }
            LOG.debug(lowerCaseParams);
        }

        @Override
        public Map getParameterMap() {
            return new ImmutableMap.Builder<String, String[]>()
                    .putAll(lowerCaseParams).build();
        }

        @Override
        public String getParameter(final String name) {
            String[] values = getParameterValues(name);
            if (values != null) {
                return values[0];
            } else {
                return null;
            }
        }

        @Override
        public Enumeration getParameterNames() {
            return asEnumeration(lowerCaseParams.keySet().iterator());
        }

        @Override
        public String[] getParameterValues(final String name) {
            return lowerCaseParams.get(name);
        }

    }

}

Code Above Contains a BUG!

From: andrew cooke <andrew@...>

Date: Sat, 7 Sep 2013 11:24:48 -0400

There's a subtle but frustrating bug above.  The contextConfigLocation loads
the servelet's context, where everything is defined.  But the delegating
servlet thing also loads that.  In my case, because I was defining schedulers
in the context, I ended up with TWO Quartz schedulers running parallel, and
all tasks being run TWICE.

The solution is simple - separate things into different context files (in my
case I just moved the filter into a completely separate file context file;
more generally you might want ot separate presentation and mid-layer beans).

Andrew

Comment on this post