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<String, String[]> params;
 
    public ParameterRequestWrapper(HttpServletRequest request,
            Map<String, String[]> 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<String, String[]> getParameterMap() {
        return params;
    }
 
    @Override
    public Enumeration<String> getParameterNames() {
        return new Vector<String>(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<String, String[]> m = new HashMap<String, String[]>(
                request.getParameterMap());
        request = new ParameterRequestWrapper((HttpServletRequest) request, m);
 
        chain.doFilter(request, response);
    }
 
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
 
    }
 
}

3. web.xml

<!-- request参数转化器 -->
<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>  

本文转自：http://blog.csdn.net/a9529lty/article/details/25478989