第一个过滤器Filter

过滤器实现Filter接口javax.servlet.Filter

package com.henau.example;

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;

public class FilterDemo1 implements Filter {

	@Override
	public void destroy() {
		System.out.println("过滤器1销毁了");

	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("调用过滤器1");
		chain.doFilter(request, response);
		System.out.println("调用过滤器1");

	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("过滤器初始化1");

	}

}

配置web.xml（表示过滤所有目录）

 <filter-name>FilterDemo1</filter-name>
    <filter-class>com.henau.example.FilterDemo1</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>FilterDemo1</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

配置两个Filter

调用一个页面，输出的结果为

调用过滤器1
调用过滤器2
输出
调用过滤器2
调用过滤器1

调用的顺序是web.xml中的Filter-mapping的配置先后顺序而先后执行