Filter_细节_web.xml配置方式和Filter_细节_执行流程&生命周期

过滤器细节：

• web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

        <filter>
            <filter-name>demo01</filter-name>
            <filter-class>com.ailyt.filter.FilterStudy02</filter-class>
        </filter>

    <filter-mapping>
        <filter-name>demo01</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

• 过滤器执行流程
• 过滤器生命周期方法

package com.ailyt.filter;

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

@WebFilter("/*")
public class CharacterEncodingFilter implements Filter {
    /*初始化*/
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("CharacterEncoding初始化");
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");

        servletResponse.setContentType("text/html;charset=utf-8");
        //filterChain链
        /**
         * 过滤中的所有代码在过滤特定的请求的时候都会被执行
         * 必须要让过滤器继续通行
         * filterChain.doFilter(servletRequest, servletResponse);
         */
        System.out.println("CharacterEncodingFilter执行前");
        filterChain.doFilter(servletRequest, servletResponse);//让我们的请求继续走，如果不写程序到这里就会被拦截
        System.out.println("CharacterEncodingFilter执行后");
    }

    /*销毁*/
    public void destroy() {
        System.out.println("CharacterEncoding销毁");
    }
}