Making a request parameter binding case insensitive

Question

I have a requirement where I have to make requestParams to bind properly even if the cases of the param name changes. Note:I am using spring 3.2

For eg: http:/

Answer 1

You could write a servlet filter that does this. But it does need some coding work.

Here is the link to the code - http://www.acooke.org/cute/Forcinglow0.html

Something like this - in this servlet filter convert parameters to lower case

public final class LowerCaseParametersFilter implements Filter {
 @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);
    }
}
}

Here is the xml config - u wuld need

 <bean id="delegatingFilter"
      class="org.springframework.web.filter.DelegatingFilterProxy"

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

I did some research and found this Case-insensitive query string request paramters

   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;
    }

Answer 2

Spring has a LinkedCaseInsensitiveMap Which you could use to do case insensitive lookups.

An implementation could look like the following.

package biz.deinum.web.filter;

import org.springframework.util.LinkedCaseInsensitiveMap;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Map;

/**
 * Wrapper for an {@link HttpServletRequest} to make the lookup of parameters case insensitive. The functionality
 * is achieved by using the {@link LinkedCaseInsensitiveMap} from Spring.
 * 
 * @author Marten Deinum
 */
public class CaseInsensitiveRequestFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        filterChain.doFilter(new CaseInsensitiveHttpServletRequestWrapper(request), response);
    }

    private static class CaseInsensitiveHttpServletRequestWrapper extends HttpServletRequestWrapper {

        private final LinkedCaseInsensitiveMap<String[]> params = new LinkedCaseInsensitiveMap<>();

        /**
         * Constructs a request object wrapping the given request.
         *
         * @param request
         * @throws IllegalArgumentException if the request is null
         */
        private CaseInsensitiveHttpServletRequestWrapper(HttpServletRequest request) {
            super(request);
            params.putAll(request.getParameterMap());
        }

        @Override
        public String getParameter(String name) {
            String[] values = getParameterValues(name);
            if (values == null || values.length == 0) {
                return null;
            }
            return values[0];
        }

        @Override
        public Map<String, String[]> getParameterMap() {
            return Collections.unmodifiableMap(this.params);
        }

        @Override
        public Enumeration<String> getParameterNames() {
            return Collections.enumeration(this.params.keySet());
        }

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

Answer 3

Solution with implementing custom Filter.

Filter:

public final class CaseInsensitiveParametersFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) {
    }

    @Override
    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        if (request instanceof HttpServletRequest) {
            chain.doFilter(new CustomHttpServletRequestWrapper((HttpServletRequest) request), response);
        } else {
            chain.doFilter(request, response);
        }

    }

    private static class CustomHttpServletRequestWrapper extends HttpServletRequestWrapper {

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

        public CustomHttpServletRequestWrapper(HttpServletRequest request) {
            super(request);
            Map<String, String[]> originalParams = request.getParameterMap();
            for (Map.Entry<String, String[]> entry : originalParams.entrySet()) {
                lowerCaseParams.put(entry.getKey().toLowerCase(), entry.getValue());
            }
        }

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

        @Override
        public Map getParameterMap() {
            return Collections.unmodifiableMap(lowerCaseParams);
        }

        @Override
        public Enumeration getParameterNames() {
            return Collections.enumeration(lowerCaseParams.keySet());
        }

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

    }

Servlet initializer:

public class RestServiceInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    @Override
    protected Filter[] getServletFilters() {
        return new Filter[]{new CaseInsensitiveParametersFilter()};
    }
}