在包 com.example.demo.filter 下新建 FilterFilter.java 文件：

    1. package com.example.demo.filter;
    3. import org.springframework.core.annotation.Order;
    5. import javax.servlet.*;
    6. import javax.servlet.annotation.WebFilter;
    7. import java.io.IOException;
    9. /**
    10.  * @author Where
    11.  */
    12. @Order(1)
    13. @WebFilter(filterName = "FirstFilter", urlPatterns = "/")
    14. public class FirstFilter implements Filter {
    15.     @Override
    16.     public void init(FilterConfig filterConfig) throws ServletException {
    18.     }
    20.     @Override
    21.     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    22.         System.out.println("FirstFilter");
    23.     }
    25.     @Override
    26.     public void destroy() {
    28.     }
    29. }

    在 Application.java 上添加 @ServletComponentScan 注解：

    1. package com.example.demo;
    3. import org.springframework.boot.SpringApplication;
    4. import org.springframework.boot.autoconfigure.SpringBootApplication;
    5. import org.springframework.boot.web.servlet.ServletComponentScan;
    7. /**
    8.  * Application
    9.  *
    10.  * @author Where
    11.  */
    12. @SpringBootApplication
    13. @ServletComponentScan
    14. public class Application {
    15.     public static void main(String[] args) {
    16.         SpringApplication.run(Application.class, args);
    17.     }
    18. }

    重新启动应用，访问 http://localhost:8080 查看控制台。