SSH架构，dao层如何调用HTTPSession中存储的值

SSH架构，dao层怎么调用HTTPSession中存储的值
如题，

在dao层，怎么调用到HTTPSession中存储的userId

不想从 action传参，因为很多地方调用dao层的方法，传参修改量非常大。

如果不用session，应该用什么能实现这个效果啊？

随时随地能取到userId??

------解决方案--------------------------------------------------------
过滤器里面 把session放到threadlocal中。
package com.shangwang.util;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
 * 由于Spring 的AOP面向切面编程，与Servlet容器没有任何关联，所以想要获得Session会话比较麻烦。
在Servlet中或struts1中，可以通过ThreadLocal方式将session保存，Spring AOP中获得Session对象。
 * @author Administrator
 *
 */
public class SysContent {
private static ThreadLocal<HttpServletRequest> requestLocal= new ThreadLocal<HttpServletRequest>();
private static ThreadLocal<HttpServletResponse> responseLocal= new ThreadLocal<HttpServletResponse>();

public static HttpServletRequest getRequest() {
return (HttpServletRequest)requestLocal.get();
}
public static void setRequest(HttpServletRequest request) {
requestLocal.set(request);
}
public static HttpServletResponse getResponse() {
return (HttpServletResponse)responseLocal.get();
}
public static void setResponse(HttpServletResponse response) {
responseLocal.set(response);
}
public static HttpSession getSession() {
return (HttpSession)((HttpServletRequest)requestLocal.get()).getSession();
}
}


过滤器
package com.shangwang.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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.shangwang.util.SysContent;

public class GetContentFilter implements Filter {
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
SysContent.setRequest((HttpServletRequest) arg0);
SysContent.setResponse((HttpServletResponse) arg1);
arg2.doFilter(arg0, arg1);
}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
} 


这样就可以用sysContent.getSession了。