java修改request的paramMap

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最近做项目，发现要修改request的参数内容。因为想要在request的paramMap里面默认注入,modifier和modifierName,这些内容。但是这个Map是不能修改的。所以采用了如下办法：下面的办法网上也有的这里只做备份。

1. 创建request转换器

package com.tmall.lafite.web.base;import java.util.Enumeration;import java.util.Map;import java.util.Vector;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper;class ParameterRequestWrapper extends HttpServletRequestWrapper {private Map<String, String[]> params;public ParameterRequestWrapper(HttpServletRequest request,Map<String, String[]> newParams) {super(request);this.params = newParams;// RequestDispatcher.forward parameterrenewParameterMap(request);}@Overridepublic 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;}@Overridepublic Map<String, String[]> getParameterMap() {return params;}@Overridepublic Enumeration<String> getParameterNames() {return new Vector<String>(params.keySet()).elements();}@Overridepublic 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 });}}}}}}

2. 转换filter

package com.tmall.lafite.web.base;import java.io.IOException;import java.util.HashMap;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;public class ParamFilter implements Filter{@Overridepublic void init(FilterConfig filterConfig) throws ServletException {// TODO Auto-generated method stub}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {Map<String,String[]> m = new HashMap<String,String[]>(request.getParameterMap());  request = new ParameterRequestWrapper((HttpServletRequest)request, m);    chain.doFilter(request, response); }@Overridepublic void destroy() {// TODO Auto-generated method stub}}

3. web.xml

<!-- request參數轉換器 --><filter><filter-name>ParameterFilter</filter-name><filter-class>com.tmall.lafite.web.base.ParamFilter</filter-class></filter><filter-mapping>      <filter-name>ParameterFilter</filter-name>      <url-pattern>/*</url-pattern>      <dispatcher>REQUEST</dispatcher>      <dispatcher>FORWARD</dispatcher>  </filter-mapping>

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