SpringBoot中使用Filter（过滤器）

1. 入门

1.1 编写实体类

@Component
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Message {
    private Date date;
    private String msg ;
    private String title;
}

1.2 编写过滤器

@WebFilter(urlPatterns = "/message/*",filterName = "filter1")
public class MessageFilter1 extends HttpFilter {
    @Override
    protected void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
        if("/message/echo".equals(request.getRequestURI())) {
            String title = request.getParameter("title");
            System.out.println("【filter1】拦截到的请求的title参数内容为:"+title);
        }
//        将请求传递给链中的下一个过滤器或目标Servlet
        chain.doFilter(request,response);
    }
}

1.3 编写Controller

@RestController
@RequestMapping("/message")
public class MessageController {
    @Resource
    private Message message ;
    @RequestMapping("/echo")
    public Message echo(String msg,String title) {
        message.setTitle(title);
        message.setMsg(msg);
        return message;
    }

}

1.4 在启动类上开启servlet组件扫描（@ServletComponentScan）

@SpringBootApplication
@ServletComponentScan   //开启servlet组件扫描
public class MicrobootWebApplication {

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

}

1.5 测试并观察控制台打印情况

http://localhost:8083/message/echo?msg=西红柿战争&title=两败俱伤

2. 进阶

2.1 过滤器简单介绍

过滤器（Filter）是Java Web应用中一种用于处理请求（request）和响应（response）的组件

过滤器和的执行顺序：

• 过滤器（预处理）
• 过滤器（后处理）
• （前处理）
• 控制器方法（Controller)
• （后处理）
• 过滤器（后处理）

2.2 编写过滤器类

//过滤器1,因为有了配置类，不再需要添加@WebFilter注解
public class MessageFilter1 extends HttpFilter {
    @Override
    protected void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
        if("/message/echo".equals(request.getRequestURI())) {
            String title = request.getParameter("title");
            System.out.println("【filter1】拦截到的请求的title参数内容为:"+title);
        }
        chain.doFilter(request,response);
    }
}

public class MessageFilter2 extends HttpFilter {
    @Override
    protected void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
        if("/message/echo".equals(request.getRequestURI())) {
            String msg = request.getParameter("msg");
            System.out.println("【filter2】拦截到的请求的title参数内容为:"+msg);
        }
        chain.doFilter(request,response);
    }
}

2.3 编写过滤器配置类

//过滤器配置类
@Configuration
public class WebFilterConfig {

    @Bean
    public FilterRegistrationBean getFilter1Registration() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(this.getMessageFilter1());
        //设置过滤器名称和路径，在过滤器类写了的话，这里不用重复写
        filterRegistrationBean.setName("filter");
        filterRegistrationBean.addUrlPatterns("/*");
        //设置过滤器执行顺序，数字越小，越早进行过滤，也可设置为负数
        filterRegistrationBean.setOrder(1);
        return filterRegistrationBean;
    }

    @Bean
    public FilterRegistrationBean getFilter2Registration() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(this.getMessageFilter2());
        //设置过滤器执行顺序
        filterRegistrationBean.setOrder(2);
        return filterRegistrationBean;
    }

    @Bean
    public MessageFilter1 getMessageFilter1() {
        return new MessageFilter1();
    }

    @Bean
    public MessageFilter2 getMessageFilter2() {
        return new MessageFilter2();
    }
}

2.4 Controller和实体类和之前一样，启动类的servlet组件扫描可去除

//@ServletComponentScan   //开启servlet组件扫描
public class MicrobootWebApplication {

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

}

2.5 启动程序并观察控制台

http://localhost:8083/message/echo?msg=西红柿战争&title=两败俱伤

filter1比filter2先启用，执行成功。