Springboot使用Filter以及踩过的坑

在Springboot中使用Filter有两种方式，注解方式，注册bean方式

一、注解@WebFilter

1、实现Filter接口（javax.servlet）

2、添加@WebFilter注解

3、启动类添加@ServletComponentScan注解

附上代码：

第一个Filter：

@Slf4j

@WebFilter(filterName = "filter1", urlPatterns = {"/url1/*"})

public class Filter1_Filter implements Filter {

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        log.info("do filter1");

        filterChain.doFilter(servletRequest, servletResponse);

    }

    @Override

    public void destroy() {

    }

}

第二个Filter：

@Slf4j

@WebFilter(filterName = "filter2", urlPatterns = {"/url2/*"})

public class Filter2_Filter implements Filter {

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        log.info("do filter2");

        filterChain.doFilter(servletRequest, servletResponse);

    }

    @Override

    public void destroy() {

    }

}

启动类：

@SpringBootApplication

@ServletComponentScan

public class MyApplication {

    public static void main(String[] args) {

        SpringApplication.run(MyApplication .class, args);

    }

}

下面说说我踩过的坑

1、不加@ServletComponentScan注解无法注入Filter，这个注解的作用就是去扫描@WebServlet、@WebFilter、@WebListener这类特殊注解。如果不加，spring容器是不会主动扫描的

2、多个Filter的执行顺序，说出来你可能不信，这种注解方式实现的Filter是通过Filter的类名首字母来控制执行顺序的，像Filter1_Filter就比Filter2_Filter先执行。但网上一些资料说，当Filter数量很多时，是没有明确的执行顺序的，所以这种方式还是放弃吧，推荐第二种

二、注册bean

1、实现Filter接口

2、注册Filter

下面附上代码：

第一个Filter：

@Slf4j

public class Filter1 implements Filter {

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        log.info("do filter1");

        filterChain.doFilter(servletRequest, servletResponse);

    }

    @Override

    public void destroy() {

    }

}

第二个Filter：

@Slf4j

public class Filter2 implements Filter {

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        log.info("do filter2");

        filterChain.doFilter(servletRequest, servletResponse);

    }

    @Override

    public void destroy() {

    }

}

注册类：

@Configuration

public class FilterConfig {

    @Bean

    public Filter filter1(){

        return new Filter1();

    }

    @Bean

    public Filter filter2(){

        return new Filter2();

    }

    @Bean

    public FilterRegistrationBean setFilter1() {

        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();

        filterRegistrationBean.setFilter(filter1());

        filterRegistrationBean.addUrlPatterns("/url1/*");

        filterRegistrationBean.setOrder(1);   //order的数值越小，在所有的filter中优先级越高

        return filterRegistrationBean;

    }

    @Bean

    public FilterRegistrationBean setFilter2(){

        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();

        filterRegistrationBean.setFilter(filter2());

        filterRegistrationBean.addUrlPatterns("/url2/*");

        filterRegistrationBean.setOrder(2);   //order的数值越小，在所有的filter中优先级越高

        return filterRegistrationBean;

    }

}

这种方式就比较严谨了，通过filterRegistrationBean.setOrder(1)设置执行顺序亲测有效