Spring Boot 自定义Filter

一、Filter功能

它使用户可以改变一个 request和修改一个response. Filter 不是一个servlet,它不能产生一个response,它能够在一个request到达servlet之前预处理request,也可以在离开 servlet时处理response.换种说法,filter其实是一个 “servlet chaining” (servlet 链).

一个Filter包括：

1）、在servlet被调用之前截获;

2）、在servlet被调用之前检查servlet request;

3）、根据需要修改request头和request数据;

4）、根据需要修改response头和response数据;

5）、在servlet被调用之后截获.

二、自定义Filter

• 方法一：

1. 实现filter方法

   public class GlobalFilter implements Filter {
       @Override
       public void init(FilterConfig filterConfig) throws ServletException {
   
       }
   
       @Override
       public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
           HttpServletRequest request = (HttpServletRequest) servletRequest;
           String requestURI = request.getRequestURI();
           System.out.println(requestURI);
           filterChain.doFilter(request, servletResponse);
       }
   
       @Override
       public void destroy() {
   
       }
   }
   

2. 加载Filter 配置

   @Configuration
   public class FilterConfig {
   
       @Bean
       public FilterRegistrationBean filterRegistration(){
           // 新建过滤器注册类
           FilterRegistrationBean registration = new FilterRegistrationBean();
           // 添加自定义 过滤器
           registration.setFilter(globalFilter());
           // 设置过滤器的URL模式
           registration.addUrlPatterns("/*");
           //设置过滤器顺序
           registration.setOrder(1);
           return registration;
       }
       @Bean
       public GlobalFilter globalFilter(){
           return new GlobalFilter();
       }
   }
   

• 方法二（推荐）

  1. 自定义MyFilter, 如果请求URI 包含 my ， 则进行下一步处理

     @WebFilter(filterName = "myFilter", urlPatterns = "/*")
     public class MyFilter implements Filter {
     
         @Override
         public void init(FilterConfig filterConfig) throws ServletException {
             System.out.println("init...");
         }
     
         @Override
         public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
             HttpServletRequest request = (HttpServletRequest) servletRequest;
             String requestURI = request.getRequestURI();
             if(requestURI.contains("my")){
                 System.out.println("成功啦。。。, 请求URI是:" + requestURI);
             }
             filterChain.doFilter(request, servletResponse);
         }
     
         @Override
         public void destroy() {
             System.out.println("destroy...");
         }
     }
     

  2. 在Application 启动类 添加 @ServletComponentScan 注解

     @ServletComponentScan
     @SpringBootApplication
     public class Application {
     
         public static void main(String[] args) {
             SpringApplication.run(Application.class, args);
         }
     }