防盗链

一.防盗链
　　在页面中请求不属于自己的资源, 可以增加自己的流量, 耗费别人的宽带.

Demo: 防止倒链(使用过滤器)

@WebFilter(urlPatterns="/img/*")
public class ChainFilter implements Filter {
    @Override
    public void destroy() {
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        //向下转型
        HttpServletRequest req = (HttpServletRequest)request;
        HttpServletResponse resp = (HttpServletResponse)response;
        
        String str = req.getHeader("referer");
        System.out.println(str);
        if (str.contains("sxtpms")) {
            chain.doFilter(req, resp);
        } else {
            resp.getWriter().println("不可以盗链!");
        }
    }
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
}