Case-insensitive query string request parameters

Question

My goal is that all below URI's should work

https://rest/xyz?sort=name

https://rest/xyz?Sort=name

https://rest/xyz?filter=name=value

https://rest/xyz?Filter=name=value

To achieve this, I have created custom filter that overrides the HttpServletRequest that is passed to the FilterChain. Below is the link for this approach:

http://forum.springsource.org/archive/index.php/t-87433.html

My code:

import java.io.IOException;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper; 

public class HttpCustomParamFilter implements Filter
{
    private static class HttpServletRequestCustomeWrapper extends HttpServletRequestWrapper
    {
        private String[] parameterValues;

        @Override
        public String[] getParameterValues(String name)
        {
            Map<String, String[]> localParameterMap = super.getParameterMap();

            // Handle case insensitivity of http request paramters like start, count, query, sort, filter etc.
            if (localParameterMap != null && !localParameterMap.isEmpty())
            {
                parameterValues = new String[localParameterMap.size()];
                for (String key : localParameterMap.keySet())
                {
                    if (name.equalsIgnoreCase(key))
                        parameterValues = localParameterMap.get(key);
                    else
                        parameterValues = null;
                }
            }
            return parameterValues;
        }

        public HttpServletRequestCustomWrapper(final ServletRequest request)
        {
            super((HttpServletRequest) request);
        }


    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {
        // override the request passed to the FilterChain
        chain.doFilter(new HttpServletRequestCustomWrapper(request), response);
        }

    @Override
    public void init(FilterConfig filterConfig)
            throws ServletException
    {
        // TODO Auto-generated method stub

    }

    @Override
    public void destroy()
    {
        // TODO Auto-generated method stub

    }

}

In this code, i have overriden getParameterValues(String name) method and achieved case-insensitivity of request paramters, but not sure if i need to override any other methods.

my doubts:

• do i need to override other methods also like getParameter() and getParameterNames()?

• what internal implementation is impacted with this?

• which class i can see the code implementation of getParameter(), getParameterNames() and getParameterValues()?

Answer 1

First, let me say my peace: I don't think modifying the HttpServletRequestWrapper is the way to go. I am not even sure how you would go about using it, as my understanding is it's App Server specific. As a side note, this article has specifics on how to use the HttpServletRequest to get a case-insensitive query param without rolling your own.

But, in the spirit of answering your questions:

1. Do you need to override getParameter() and getParameterNames()? You could, as it would give you the ability to manipulate the case. In fact, I would say the safest way to make the query parameters case-insensitive would be to overwrite ONLY those methods. Make the getParameter() call do a case-insensitive equals on the string names. Not sure what you would do with getParameterNames(), maybe return every possible case, but this seems redundant.
2. What internal implementation is impacted by this? I am not certain. HttpServletRequest is so core to pretty much everything, there is no telling what you could introduce if your code is not 100% solid. For instance, Spring has a SecurityContextHolderAwareRequestWrapper, so does that mean you just broke Spring Security? No telling without a lot of testing.
3. Which class can I see the code implementation of getParameter(), getParameterNames(), and getParameterValues()? HttpServletRequestWrapper is the only implementation of HttpServletRequest interface, according to the JavaDocs. The actual implementation of this class is dependent on your application container. For instance, in my app its weblogic.servlet.internal.ServletRequestImpl, since I use Web Logic. Hopefully you are using an open-source app server that has the code readily available. The way I found this was to put a break in one of my Controller handler methods that has HttpServletRequest defined and viewing it's getClass() response in the debugger.