Springboot中Filter的使用

在Springboot中使用Filter有两种方式，注解@WebFilter方式和注册bean方式；

一、注解@WebFilter方式

1. 实现Filter接口（javax.servlet）;

2. 添加@WebFilter注解；

3. 启动类添加@ServletComponmentScan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的方式

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。

注意：

SpringBootApplication上使用@ServletComponentScan注解后，Servlet、Filter、Listener

可以直接通过@WebServlet、@WebFilter、@WebListener注解自动注册，无需其他代码。

转载自：https://www.cnblogs.com/javafucker/p/10144958.html