轻松搞定自定义Filter（过滤器）

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过滤器Filter，是Servlet的的一个实用技术了。可通过过滤器，对请求进行拦截，比如读取session判断用户是否登录、判断访问的请求URL是否有访问权限(黑白名单)等。主要还是可对请求进行预处理。接下来介绍下，在springboot如何实现过滤器功能

@WebFilte

利用@WebFilter注解配置

//注册器名称为customFilter,拦截的url为所有
@WebFilter(filterName="customFilter",urlPatterns={"/*"})
@Slf4j
@Configuration
public class CustomFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        //项目启动时初始化,只始化一次
        log.info("filter 初始化");
    }

    @Override
    public void doFilter(ServletRequest servletRequest,
                         ServletResponse servletResponse, FilterChain filterChain)
            throws IOException, ServletException {
        log.info("doFilter 请求处理");
        //对request、response进行一些预处理
        // 比如设置请求编码
        // servletRequest.setCharacterEncoding("UTF-8");
        // servletResponse.setCharacterEncoding("UTF-8");
        //链路 直接传给下一个过滤器
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {
        log.info("filter 销毁");
    }
}

FilterRegistrationBean方式

两个步骤：

1. 实现Filter接口，实现Filte

   public class MyFilter implements Filter {
   @Override
   public void destroy() {
   // TODO Auto-generated method stub
   }

    	@Override
    	public void doFilter(ServletRequest srequest, ServletResponse sresponse, FilterChain filterChain)
    			throws IOException, ServletException {
    		// TODO Auto-generated method stub
    		HttpServletRequest request = (HttpServletRequest) srequest;
    		System.out.println("this is MyFilter,url :"+request.getRequestURI());
    		filterChain.doFilter(srequest, sresponse);
    	}
   
    	@Override
    	public void init(FilterConfig arg0) throws ServletException {
    		// TODO Auto-generated method stub
    	}
    }
   

   }

2. 添加@Configuration 注解，将自定义Filter加入过滤链

   @Configuration
   public class WebConfiguration {
   @Bean
   public RemoteIpFilter remoteIpFilter() {
   return new RemoteIpFilter();
   }

    @Bean
    public FilterRegistrationBean testFilterRegistration() {
   
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new MyFilter());
        registration.addUrlPatterns("/*");
        registration.addInitParameter("paramName", "paramValue");
        registration.setName("MyFilter");
        registration.setOrder(1);
        return registration;
    }
   

   }