Filter-细节-过滤器拦截方式配置、Filter-细节-过滤器链(多个过滤器)

Filter-细节-过滤器拦截方式配置

拦截方式配置：资源被访问的方式

　　注解配置：

　　设置dispatchTypes属性

　　　　1.REQUEST：默认值。浏览器直接请求资源

　　　　2.FORWARD：转发访问资源

　　　　3.INCLUDE：包含访问资源

　　　　4.ERROR：错误跳转资源

　　　　5.ASYNC：异步访问资源

FilterDemo5类

package com.example.filter;

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

/**
 * 过滤器快速入门
 */

//浏览器直接请求index.jsp资源时，该过滤器会被执行
//@WebFilter(value="/index.jsp",dispatcherTypes = DispatcherType.REQUEST)

//只有转发index.jsp时，该过滤器才会被执行
//@WebFilter(value="/index.jsp",dispatcherTypes = DispatcherType.FORWARD)


//浏览器直接请求index.jsp资源或者转发index.jsp，该过滤器会被执行
@WebFilter(value="/index.jsp",dispatcherTypes ={ DispatcherType.FORWARD})
public class FilterDemo5 implements Filter {


    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("FitterDemo5......");
    }

    @Override
    public void destroy() {
        
    }
}

web.xml配置

　　　　设置<dispatcher></dispatcher>标签即可

<?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>demo1</filter-name>
        <filter-class>com.example.filter.FilterDemo1</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>demo1</filter-name>

        <!-- 拦截路径-->
        <url-pattern>/*</url-pattern>

        <!-- <dispatcher>REQUEST</dispatcher>
        <dispatcher>FORWARD</dispatcher>
        <dispatcher>INCLUDE</dispatcher>
        <dispatcher>ERROR</dispatcher>-->
        <dispatcher>ASYNC</dispatcher>
    </filter-mapping>

</web-app>

Filter-细节-过滤器链（多个过滤器）

过滤器链（配置多个过滤器）

　执行顺序：如果有两个过滤器：过滤器1和过滤器2

　　1.过滤器1

　　2.过滤器2

　　3.资源执行

　　4.过滤器2

　　5.过滤器1

FilterDemo6类

package com.example.filter;

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

@WebFilter(value="/*")
public class FilterDemo6 implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("FitterDemo6......");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("FitterDemo6回来了");
    }

    @Override
    public void destroy() {
        
    }
}

FilterDemo7类

package com.example.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
@WebFilter(value="/*")
public class FilterDemo7 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("FitterDemo7......");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("FitterDemo7回来了");
    }
    @Override
    public void destroy() {
        
    }
}

运行代码，访问index.jsp

过滤器先后顺序问题：

1. 注解配置：按照类名的字符串比较规则比较，值小的先执行

　　如： AFilter 和 BFilter，AFilter就先执行了。

2. web.xml配置： <filter-mapping> 谁定义在上边，谁先执行