Spring Boot使用过滤器Filter过程解析

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

@Order(1)
@WebFilter(filterName = "piceaFilter", urlPatterns = "/*" , initParams = {
    @WebInitParam(name = "URL", value = "http://localhost:8080")})
public class PiceaFilter implements Filter {

  private String url;
  /**
   * 可以初始化Filter在web.xml里面配置的初始化参数
   * filter对象只会创建一次，init方法也只会执行一次。
   * @param filterConfig
   * @throws ServletException
   */
  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    this.url = filterConfig.getInitParameter("URL");
    System.out.println("我是过滤器的初始化方法！URL=" + this.url + "，生活开始.........");
  }

  /**
   * 主要的业务代码编写方法
   * @param servletRequest
   * @param servletResponse
   * @param filterChain
   * @throws IOException
   * @throws ServletException
   */
  @Override
  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    System.out.println("我是过滤器的执行方法，客户端向Servlet发送的请求被我拦截到了");
    filterChain.doFilter(servletRequest, servletResponse);
    System.out.println("我是过滤器的执行方法，Servlet向客户端发送的响应被我拦截到了");
  }

  /**
   * 在销毁Filter时自动调用。
   */
  @Override
  public void destroy() {
    System.out.println("我是过滤器的被销毁时调用的方法！，活不下去了................" );
  }
}

@RestController
public class PiceaContoller {

  @RequestMapping("/query")
  public void asyncTask() throws Exception {
    System.out.println("我是控制类里面的方法，我正在思考...............");
  }
}

@SpringBootApplication
@ServletComponentScan
public class SpringBootFiFilterApplication {

  public static void main(String[] args) {
    SpringApplication.run(SpringBootFiFilterApplication.class, args);
  }

}