在ajax中servlet中doGet和doPost方法与xmlhttp.open("get或post",url);的关系

很好理解。
get是通过response从服务器拿信息
post 是用request给服务器发信息

就是这么规定的

使用 过滤器 可避免response.setCharacterEncoding(encoding); 和request.setCharacterEncoding(encoding);

过滤器 及其配置
package com.cnpqsoft.filter;

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;

public class EncodingFilter implements Filter
{
private String encoding = "GBK";

public void destroy()
{
}

public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException
{
arg0.setCharacterEncoding(encoding);
arg1.setCharacterEncoding(encoding);
arg2.doFilter(arg0, arg1);
}

public void init(FilterConfig arg0) throws ServletException
{
this.encoding = arg0.getInitParameter("encoding");
}

/*


EncodingFilter
com.cnpqsoft.filter.EncodingFilter

encoding
GBK




EncodingFilter
/*

*/
}