Filter

概念

快速入门

执行流程

package com.itheima.web.filter;
import javax.servlet.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebFilter("/*")
public class FilterDemo implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
// 先执行放行前的，放行前对request数据进行处理
        System.out.println("1. FilterDemo...");
        // 放行
        chain.doFilter(request, response);
        // 这是放行后的代码，放行后，对Response 数据进行处理
        System.out.println("3. FilterDemo...");
    }
    public void init(FilterConfig config) throws ServletException {
    }
    public void destroy() {
    }
}