驗證過濾器進行權限驗證的原理。

創建Filter：

package com.example.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;@WebFilter(urlPatterns = "/*")
public class DemoFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException{System.out.println("init初始化方法執行了");}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain)throws IOException,ServletException{System.out.println("攔截到了請求");}@Overridepublic void destroy(){System.out.println("destroy銷毀方法執行了");}}