拦截器解决乱码问题
过滤器用法：
@WebFilter(filterName="nn",urlPatterns="/*")
public class myfilter implements Filter{
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
// TODO Auto-generated method stub
System.out.println("ok");
chain.doFilter(request, response);
}
}//实现接口，使用注解，chain.doFilter方法释放请求