java web过滤器

package Filter;

import javax.servlet.*;
import java.io.IOException;

public class LoginFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        String name  = request.getParameter("name");
        if (name == null){
            System.out.println("请输入姓名");
            response.getWriter().write("请输入姓名");
            return;
        }else {
            chain.doFilter(request,response);
        }

    }

    @Override
    public void destroy() {

    }
}

web.xml

<filter>
   <filter-name>loginFilter</filter-name>
   <filter-class>Filter.LoginFilter</filter-class>
</filter>
<filter-mapping>
   <filter-name>loginFilter</filter-name>
   <url-pattern>/login/in</url-pattern>
</filter-mapping>