过滤器

过滤器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_3_1.xsd"
         version="3.1">
    <filter>
        <filter-name>Demo1Filter</filter-name>
        <filter-class>filter.Demo1Filter</filter-class>
        <init-param>
            <param-name>param1</param-name>
            <param-value>value在这里呢</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>Demo1Filter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher> <!-- 没有配置dispatcher就是默认request方式的 -->
        <dispatcher>FORWARD</dispatcher>
        <dispatcher>ERROR</dispatcher>
        <dispatcher>INCLUDE</dispatcher>
    </filter-mapping>
</web-app>

　一个过滤器Java代码

package filter;

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

/**
 * <Description> 
 * @classname Demo1Filter
 * @author zhouyufei
 * @taskId:
 * @version 1.0
 * @createDate 2019/11/20 9:19 
 * @see filter
 */
public class Demo1Filter implements Filter {
    private FilterConfig filterConfig;

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException
    {
        System.out.println("Demo1过滤前");
        System.out.println(filterConfig.getInitParameter("param1"));
        chain.doFilter(request, response);//放行。让其走到下个链或目标资源中
        System.out.println("Demo1过滤后");
        // 获取访问地址
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
        //  获取端口
        int localPort = request.getLocalPort();
        System.out.println(localPort);
        String localAddr = request.getLocalAddr();
        System.out.println(localAddr);

    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("初始化了");
        this.filterConfig = filterConfig;
    }

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