ajax向servlet请求时，filter拦截后进行字符过滤后不能跳转到servlet中

RT，代码如下：
js:

 <script>
        $(function() {
            $('#login_button').unbind("click").bind("click",function() {
                                $.ajax({
                                    type : 'POST',
                                    url : '${pageContext.request.contextPath}/userBiz?action=login',
                                    data : $('#login_form').serialize(),                                                                                
                                    success : function(data) {
                                                            if(data==1){
                                                                alert("登陆成功");
                                                                location.reload();  
                                                            }
                                                            if (data== 2) {
                                                                alert("用户名或密码错误，请重新登录");                                                                                                                                
                                                            }                                                           
                                                            },
                                     error :function(XMLHttpRequest, textStatus, errorThrown,dataType){
                                        alert(XMLHttpRequest.responseText);
                                        alert(XMLHttpRequest.status); 
                                        alert(XMLHttpRequest.readyState); 
                                        alert(textStatus); 
                                        alert(errorThrown);
                                        alert(dataType);
                                    }
                                        })
                            })
        })
    </script>

filter:

 package com.nun.ha.web.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.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.HttpServlet;

@WebFilter(filterName="EncodingFilter",value="/*",initParams={@WebInitParam(name="encoding",value="utf-8")})

public class EncodingFilter extends HttpServlet implements Filter{

    private static final long serialVersionUID = 1L;
    private String encoding; 
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {

        request.setCharacterEncoding(this.encoding);
        response.setCharacterEncoding(this.encoding);
        chain.doFilter(request, response);

    }

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

}

/userBiz?action=login

POST的url可以这样？
我不懂，就是问问