拦截response的响应内容，应该用什么表达？（如果响应只有一段话）

package com.filter.second;

import java.io.IOException;

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;

import javax.servlet.http.HttpServletResponse;

public class FilterSecond implements Filter {

private String ecode;

@Override

public void destroy() {

// TODO Auto-generated method stub

}

@Override

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

throws IOException, ServletException {

// TODO Auto-generated method stub

HttpServletRequest req=(HttpServletRequest) request;

HttpServletResponse res=(HttpServletResponse)response;

req.setCharacterEncoding(ecode);

res.setContentType("text/html;charset="+ecode);

System.out.println("拦截到"+req.getRequestURI());

System.out.println("拦截到");

chain.doFilter(request, response);

}

@Override

public void init(FilterConfig filterConfig) throws ServletException {

// TODO Auto-generated method stub

ecode=filterConfig.getInitParameter("ecode");

System.out.println("初始化完成,且ecode的值为："+ecode);

}

}