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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


In web.xml:





In dispatch-servlet.xml:

    <bean id="delegatingFilter"

    <bean id="lowerParams"

And the code itself:

public final class LowerCaseParametersFilter implements Filter {

    private static final Logger LOG =

    public void init(final FilterConfig filterConfig) throws ServletException

    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),
        } else {
            LOG.warn(format("Not wrapping request: %s", request.getClass()));
            chain.doFilter(request, response);

    public void destroy() {

    private static class LowerCaseRequest extends HttpServletRequestWrapper {

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

        public LowerCaseRequest(final HttpServletRequest 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]);

        public Map getParameterMap() {
            return new ImmutableMap.Builder<String, String[]>()

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

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

        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).


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