自定义过滤器

1，java 代码中实现过滤器 通过实现import javax.servlet.Filter;接口

2，web.xml 配置需要通过过滤器的请求

package com.mvc.filter.user;

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 javax.servlet.http.HttpSession;


public class UserFilter implements Filter {
	@Override
	public void destroy() {

	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain fc) throws IOException, ServletException {
		HttpSession session = ((HttpServletRequest) req).getSession();
		HttpServletRequest request = (HttpServletRequest) req;
		String reqPath = request.getRequestURI();
		if (reqPath.contains("login.do")) {
			fc.doFilter(req, resp);
		} else {
			if (session.getAttribute("loginUser") != null) {
				fc.doFilter(req, resp);
			} else {
				HttpServletResponse response = (HttpServletResponse) resp;
				response.sendRedirect("/login.jsp");
			}
		}
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {

	}

}

    <filter>
        <filter-name>userFilter</filter-name>
        <filter-class>com.mvc.filter.user.UserFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>userFilter</filter-name>
        <url-pattern>*.do</url-pattern>
    </filter-mapping>