Sample Code modify http request using servlet filter

Here is some sample code:

   public class removeEQFilter extends GenericFilter {


          efastConstants eC = new efastConstants();
             com.decipher.util.decipherLogger lf = new com.decipher.util.decipherLogger(eC.EFAST);
            decipherStringUtil dsu = new decipherStringUtil(eC.EFAST);



       public void doFilter(final ServletRequest request, final ServletResponse response, FilterChain chain) throws IOException, ServletException
       {


                  String paramName = "";
                  String paramValue = "";
                  int count = 0;

                  try{

                lf.logDebugMessage("Entering removeEQFilter.doFilter");
                lf.logDebugMessage(" ");

                HttpServletRequest oldRequest = (HttpServletRequest)request;

                HttpRequestWithModifiableParameters myReq = new HttpRequestWithModifiableParameters(oldRequest);


                      Enumeration names =  myReq.getParameterNames();  //retrieving ParameterNames

                      while (names.hasMoreElements()) {                       // #1 Loop Thru All ParameterNames

                              count++;                                                     // incrementing count
                              paramName = (String) names.nextElement();    // setting      paramName

                    if (paramName!=null&&paramName.equalsIgnoreCase("nextPage")) {

                                   // skip paramName = 'nextPage'
                              }
                            else {

                           String lkpEqualSign = "";
                           String cnvField = "";

                           /*
                              Need to determine if the paramName has multiple occurrences
                           */

                           String[] lkpFields = null;
                           //String[] tempFields = null;

                           lkpFields = myReq.getParameterValues(paramName);

                           if (lkpFields!=null && lkpFields.length>0) {


                                     lf.logDebugMessage(" #1 Processing Grid Field " + paramName + " with Length = " + lkpFields.length);

                                             int i = 0;

                                             boolean performReplace = false;

                                             while (i<lkpFields.length) {  // #2 Loop Thru Multiple Grid Field Names

                                                   lkpEqualSign=lkpFields[i];


                                        if (lkpEqualSign!=null&&lkpEqualSign.indexOf('=')!=-1)  {

                                              lf.logDebugMessage(" ");
                                        lf.logDebugMessage("Need conversion on paramName[i] = " + paramName + " - " + i + " - " + lkpEqualSign);
                                              lf.logDebugMessage(" ");

                                              cnvField = dsu.subChar(lkpEqualSign, "=", "", false);
                                              lf.logDebugMessage("cnvField = " + cnvField);

                                        lkpFields[i] = cnvField;

                                              lf.logDebugMessage("lkpFields[i] = " + lkpFields[i]);
                                        performReplace = true;
                                        }

                                                  i++;

                                             }  // // #2 Loop Thru Multiple Grid Field Names


                                             if (performReplace) {

                                   myReq.setParameter(paramName, lkpFields);

                                             }

                                       }
                                       else {


                                 lkpEqualSign=myReq.getParameter(paramName);

                                       lf.logDebugMessage(" #2 Processing Single Screen Field " + paramName + " with Length = " + lkpFields.length);

                                     if (lkpEqualSign!=null&&lkpEqualSign.indexOf('=')!=-1)  {

                                          lf.logDebugMessage(" ");
                                    lf.logDebugMessage("Need conversion on paramName = " + paramName + " - " + lkpEqualSign);
                                          lf.logDebugMessage(" ");

                                          cnvField = dsu.subChar(lkpEqualSign, "=", "", false);
                                          lf.logDebugMessage("cnvField = " + cnvField);
                                    myReq.setParameter(paramName, cnvField);
                                    lf.logDebugMessage("After using set method = " + myReq.getParameter(paramName));
                                    }
                                          }

                                  }

                      }      // End of // #1 Loop Thru All ParameterNames

                chain.doFilter(myReq, response);

                lf.logDebugMessage("Exiting removeEQFilter.doFilter");
                lf.logDebugMessage("                     ");


                }
                  catch(Exception e){
                        com.decipher.util.decipherLogger dl = new com.decipher.util.decipherLogger(eC.EFAST);
                        dl.logException(e);
                  }



      }

public class HttpRequestWithModifiableParameters extends HttpServletRequestWrapper {

    Map params;

    /**
     * @param request
     */
    public HttpRequestWithModifiableParameters(HttpServletRequest request) {
        super(request);
        //this.params = request.getParameterMap();

        this.params = new HashMap(request.getParameterMap());

    }

    /* (non-Javadoc)
     * @see javax.servlet.ServletRequest#getParameter(java.lang.String)
     */
    public String getParameter(String name) {
        String returnValue = null;
        String[] paramArray = getParameterValues(name);
        if (paramArray != null && paramArray.length > 0){
          returnValue = paramArray[0];
        }
        return returnValue;
    }
    /* (non-Javadoc)
     * @see javax.servlet.ServletRequest#getParameterMap()
     */
    public Map getParameterMap() {
        return Collections.unmodifiableMap(params);
    }
    /* (non-Javadoc)
     * @see javax.servlet.ServletRequest#getParameterNames()
     */
    public Enumeration getParameterNames() {
        return Collections.enumeration(params.keySet());
    }
    /* (non-Javadoc)
     * @see javax.servlet.ServletRequest#getParameterValues(java.lang.String)
     */
    public String[] getParameterValues(String name) {
          String[] result = null;
          String[] temp = (String[])params.get(name);
          if (temp != null){
                result = new String[temp.length];
                System.arraycopy(temp, 0, result, 0, temp.length);
          }
        return result;
    }


    /**
     * Sets the a single value for the parameter.  Overwrites any current values.
     * @param name Name of the parameter to set
     * @param value Value of the parameter.
     */
    public void setParameter(String name, String value){
      String[] oneParam = {value};
      setParameter(name, oneParam);
    }

    /**
     * Sets multiple values for a parameter.
     * Overwrites any current values.
     * @param name Name of the parameter to set
     * @param values String[] of values.
     */
    public void setParameter(String name, String[] values){
      params.put(name, values);
    }
}