Javaweb 过滤器 开发步骤

快速入门

1、新建一个类,实现Filter接口

2、实现doFilter()方法,打印一句话,来证明能够进行拦截

3、在web.xml中进行配置(参照Servlet配置)

4、访问一个页面,看看能不能拦截

1>

package com.test.filter;

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 Demo1Filter implements Filter {
	private FilterConfig filterConfig;

	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");
	}

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

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

2>web.xml中进行配置

 
 	Demo1Filter
 	com.itheima.filter.Demo1Filter
 	
 		param1
 		value在这里呢
 	
 
 
 	Demo1Filter
 	/*
 	REQUEST 
 	FORWARD
 	ERROR
 	INCLUDE
 

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