HTTP协议和防盗链

package com.wdksoft;

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;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 过滤图片请求
 * @author FLC
 *
 */
public class ImageFilter implements Filter{

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

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("dofilter");
		//获取到当前请求的连接地址和上一个发送请求的地址
		HttpServletRequest httprequest=(HttpServletRequest)request;
		HttpServletResponse httpresponse=(HttpServletResponse)response;
		
		//获取上一个发送请求的连接
		String referer = httprequest.getHeader("Referer");
		String serverName = httprequest.getServerName();
		System.out.println(referer+"\t"+serverName);
		if(referer==null||!referer.contains(serverName)) {
			request.getRequestDispatcher("/img/002.png").forward(request, response);
			return;
		}
		
		//放行
		chain.doFilter(request, response);
		
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("过滤器启动");
	}

}