java给request添加新的参数

添加参数的初衷是想在这里加个20行一页的分页参数.试了好几种方法,下面的方法可以,记录一下.
示例如下:

Map m = new HashMap(request.getParameterMap());
        m.put("rows", new String[]{"20"});
        request = new ParameterRequestWrapper(request, m);

    public class ParameterRequestWrapper extends HttpServletRequestWrapper {

        private Map params;

        public ParameterRequestWrapper(HttpServletRequest request, Map newParams) {
            super(request);
            this.params = newParams;
            renewParameterMap(request);
        }

        @Override
        public String getParameter(String name) {
            String result = "";

            Object v = params.get(name);
            if (v == null) {
                result = null;
            } else if (v instanceof String[]) {
                String[] strArr = (String[]) v;
                if (strArr.length > 0) {
                    result = strArr[0];
                } else {
                    result = null;
                }
            } else if (v instanceof String) {
                result = (String) v;
            } else {
                result = v.toString();
            }

            return result;
        }

        @Override
        public Map getParameterMap() {
            return params;
        }

        @Override
        public Enumeration getParameterNames() {
            return new Vector(params.keySet()).elements();
        }

        @Override
        public String[] getParameterValues(String name) {
            String[] result = null;

            Object v = params.get(name);
            if (v == null) {
                result = null;
            } else if (v instanceof String[]) {
                result = (String[]) v;
            } else if (v instanceof String) {
                result = new String[]{(String) v};
            } else {
                result = new String[]{v.toString()};
            }

            return result;
        }

        private void renewParameterMap(HttpServletRequest req) {

            String queryString = req.getQueryString();

            if (queryString != null && queryString.trim().length() > 0) {
                String[] params = queryString.split("&");

                for (int i = 0; i < params.length; i++) {
                    int splitIndex = params[i].indexOf("=");
                    if (splitIndex == -1) {
                        continue;
                    }

                    String key = params[i].substring(0, splitIndex);

                    if (!this.params.containsKey(key)) {
                        if (splitIndex < params[i].length()) {
                            String value = params[i].substring(splitIndex + 1);
                            this.params.put(key, new String[]{value});
                        }
                    }
                }
            }
        }

    }

这样就可以正常从request取到自己添加的值了

String rows = request.getParameter("rows");