Filter-过滤器

Spring

过滤器：拦截请求的

过滤器怎么用？
1.创建filter实例
2.配置filter

package com.zhiyou.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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
* Servlet Filter implementation class MyFilter
*/
@WebFilter("/jsp/*")
public class MyFilter implements Filter {




    public MyFilter() {
       System.out.println("过滤器的构造函数被调用");
    }




    public void destroy() {
        System.out.println("过滤器被销毁");
    }


    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {


        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        System.out.println("执行doFilter方法");
        
        //验证是否登陆
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse res = (HttpServletResponse) response;
        Object name = req.getSession().getAttribute("name");
        if (name==null) {
            res.sendRedirect("../login.jsp");
        }
        //找到servlet，进入servlet servlet执行完回到filter
        chain.doFilter(request, response);
        System.out.println("执行完doFilter方法");
    }




    public void init(FilterConfig fConfig) throws ServletException {
        System.out.println("过滤器初始化");
    }


}

注意： 过滤器是双向的