Modifying HttpServletRequest parameters with a Servlet Filter doesn't seem to work
jsp, servlets
Solution
Your remove method modifies the mutable map returned by `getParameterMap()`. But the next call to `getParameterMap()` reconstructs a new mutable map containing all the parameters of the wrapped query.
The mutable map should be constructed when the `FilteredRequest` is constructed, and it should be stored in an instance field.
Problem
I need to remove/modify some of `HttpServletRequest` parameters. I'm trying to do so by using a `Filter` based on the question I posted a few days ago. In the `Filter`, I'm trying to wrap the `HttpServletRequest` by inheriting the `HttpServletRequestWrapper` class as follows. ``` private final static class FilteredRequest extends HttpServletRequestWrapper { public FilteredRequest(ServletRequest request) { super((HttpServletRequest) request); } @Override public String getParameter(String paramName) { return super.getParameter(paramName); } @Override public String[] getParameterValues(String paramName) { return super.getParameterValues(paramName); } @Override public Map getParameterMap() { Map<Object, Object> parameterMap = new HashMap<Object, Object>(); Map originalParameterMap = super.getParameterMap(); for (Object o : originalParameterMap.entrySet()) { Map.Entry<Object, Object> pairs = (Entry<Object, Object>) o; parameterMap.put(pairs.getKey(), pairs.getValue()); } return parameterMap; //Returning a modifiable ParameterMap. } } ``` It's an inner class within the `Filter` class. In the `doFilter()` method, ``` chain.doFilter(new FilteredRequest(request), (HttpServletResponse)response); ``` the constructor of the above class is being invoked (that wraps the request). Now, I expect any of request parameters to modify/unset in my Spring MVC controller class. I'm trying to remove the parameter in the controller class as follows. ``` Map requestMap=request.getParameterMap(); requestMap.remove("txt_country_name"); ``` Alternatively, ``` requestMap.put("txt_country_name", null); ``` Accordingly, the request parameter `txt_country_name` should be removed from the `HttpServletRequest` but it isn't removed (nor it throws any exception like "No modifications are allowed to a locked ParameterMap"). What am I missing here? Am I following a wrong way? By the way, Making/using a request attribute all the time through out the entire application doesn't seem to be the best solution. [I need to remove/modify request parameter within the Spring MVC controller class and not within the `Filter` itself]