java修改request的paramMap

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 params;

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

		// RequestDispatcher.forward parameter
		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 });
					}
				}
			}
		}
	}

}

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{

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		Map m = new HashMap(request.getParameterMap());  
		request = new ParameterRequestWrapper((HttpServletRequest)request, m);  
		  
		chain.doFilter(request, response); 
	}

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

}

3. web.xml

	
		ParameterFilter
		com.tmall.lafite.web.base.ParamFilter
	
	  
	    ParameterFilter  
	    /*  
	    REQUEST  
	    FORWARD