session中保存中文乱码有关问题

session中保存中文乱码问题
我在控制层保存了一个session.setAttribute("haha","哈哈");

然后我在变现层使用EL表达式:${sessionScope.haha}取出来的汉字是乱码，其他的JSP功能正常显示，就session取出来的汉字是乱码。思路是什么呢？如何一次性解决？因为这样的有好几处，我不想string来转码，很麻烦啊
多谢

------解决方案--------------------------------------------------------
自己写一个过滤器: 


public class DoFilter implements Filter 
{ 

public void destroy() { 
} 

public void doFilter(ServletRequest arg0, ServletResponse arg1, 
FilterChain arg2) throws IOException, ServletException { 

arg1.setCharacterEncoding("GBK"); 
arg2.doFilter(arg0, arg1); 

} 

public void init(FilterConfig arg0) throws ServletException { 
} 

} 

在web。xml中配置： 

<!-- 过滤器 --> 
<filter> 
<filter-name>encodingFilter </filter-name> 
<filter-class>org.springframework.web.filter.CharacterEncodingFilter </filter-class> 
<init-param> 
<param-name>encoding </param-name> 
<param-value>UTF-8 </param-value> 
</init-param> 
<init-param> 
<param-name>forceEncoding </param-name> 
<param-value>true </param-value> 
</init-param> 
</filter> 
<filter-mapping> 
<filter-name>encodingFilter </filter-name> 
<url-pattern>*.jsp </url-pattern> 
</filter-mapping>
<filter-mapping> 
<filter-name>encodingFilter </filter-name> 
<url-pattern>*.do </url-pattern> 
</filter-mapping>