你可以在实现javax.servlet.Filter的类上使用@WebFilter javax.servlet.annotation.WebFilter:

@WebFilter(urlPatterns = "/*")
public class MyFilter implements Filter {
}

然后使用@ServletComponentScan注册。

这是一个建议而不是答案，但如果你在你的web应用程序中使用Spring MVC，最好使用Spring HandlerInterceptor而不是Filter。

它可以做同样的工作，但是

可以使用ModelAndView吗 它的方法可以在请求处理之前和之后调用，或者在请求完成之后调用。 它很容易测试

1. 实现HandlerInterceptor接口，并向类中添加@Component注释

@Component
public class SecurityInterceptor implements HandlerInterceptor {

    private static Logger log = LoggerFactory.getLogger(SecurityInterceptor.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        request.getSession(true);
        if(isLoggedIn(request))
            return true;

        response.getWriter().write("{\"loggedIn\":false}");
        return false;
    }

    private boolean isLoggedIn(HttpServletRequest request) {
        try {
            UserSession userSession = (UserSession) request.getSession(true).getAttribute("userSession");
            return userSession != null && userSession.isLoggedIn();
        } catch(IllegalStateException ex) {
            return false;
        }
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {

    }
}

2. 配置拦截器

@Configuration
public class WebConfig implements WebMvcConfigurer {

    private HandlerInterceptor securityInterceptor;

    @Autowired
    public void setSecurityInterceptor(HandlerInterceptor securityInterceptor) {
        this.securityInterceptor = securityInterceptor;
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(securityInterceptor).addPathPatterns("/**").excludePathPatterns("/login", "/logout");
    }

}

如果您想要设置一个第三方过滤器，您可以使用FilterRegistrationBean。

例如，等价的web.xml:

<filter>
     <filter-name>SomeFilter</filter-name>
        <filter-class>com.somecompany.SomeFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>SomeFilter</filter-name>
    <url-pattern>/url/*</url-pattern>
    <init-param>
        <param-name>paramName</param-name>
        <param-value>paramValue</param-value>
    </init-param>
</filter-mapping>

这将是@Configuration文件中的两个bean:

@Bean
public FilterRegistrationBean someFilterRegistration() {

    FilterRegistrationBean registration = new FilterRegistrationBean();
    registration.setFilter(someFilter());
    registration.addUrlPatterns("/url/*");
    registration.addInitParameter("paramName", "paramValue");
    registration.setName("someFilter");
    registration.setOrder(1);
    return registration;
}

public Filter someFilter() {
    return new SomeFilter();
}

以上是用Spring Boot 1.2.3测试的。

过滤器，顾名思义，用于对资源的请求或资源的响应执行过滤，或同时对两者执行过滤。Spring Boot提供了一些选项来在Spring Boot应用程序中注册自定义过滤器。让我们看看不同的选项。

1. 定义Spring Boot过滤器和调用顺序

实现Filter接口，在Spring Boot中创建一个新的过滤器。

@Configuration
@Order(Ordered.HIGHEST_PRECEDENCE)
public class CustomFilter implements Filter {

    private static final Logger LOGGER = LoggerFactory.getLogger(CustomFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        LOGGER.info("########## Initiating Custom filter ##########");
    }

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

        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        LOGGER.info("Logging Request  {} : {}", request.getMethod(), request.getRequestURI());

        // Call next filter in the filter chain
        filterChain.doFilter(request, response);

        LOGGER.info("Logging Response :{}", response.getContentType());
    }

    @Override
    public void destroy() {
        // TODO: 7/4/2018
    }
}

让我们快速看一下上面代码中的一些要点

@Component注释注册的过滤器。 为了以正确的顺序触发过滤器，我们需要使用@Order注释。 @ component @Order (1) 公共类CustomFirstFilter实现了Filter { ｝ @ component @Order (2) 公共类CustomSecondFilter实现了Filter { ｝

在上面的代码中，CustomFirstFilter将在CustomSecondFilter之前运行。

数字越低，优先级越高

2. URL模式

如果基于约定的映射不够灵活，我们可以使用FilterRegistrationBean对应用程序进行完全控制。在这里，不要为过滤器类使用@Component注释，而是使用FilterRegistrationBean注册过滤器。

public class CustomURLFilter implements Filter {

    private static final Logger LOGGER = LoggerFactory.getLogger(CustomURLFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        LOGGER.info("########## Initiating CustomURLFilter filter ##########");
    }

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

        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        LOGGER.info("This Filter is only called when request is mapped for /customer resource");

        // Call the next filter in the filter chain
        filterChain.doFilter(request, response);
    }

    @Override
    public void destroy() {

    }
}

使用FilterRegistrationBean注册自定义过滤器。

@Configuration
public class AppConfig {

    @Bean
    public FilterRegistrationBean < CustomURLFilter > filterRegistrationBean() {
        FilterRegistrationBean < CustomURLFilter > registrationBean = new FilterRegistrationBean();
        CustomURLFilter customURLFilter = new CustomURLFilter();

        registrationBean.setFilter(customURLFilter);
        registrationBean.addUrlPatterns("/greeting/*");
        registrationBean.setOrder(2); // Set precedence
        return registrationBean;
    }
}

对于Spring Boot在我所做的任何配置类:

@Bean
public OncePerRequestFilter myFilter() {
    return new OncePerRequestFilter() {
        @Override
        protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
            AuthUser authUser = SecurityUtil.safeGet(); // applied after secutiry filters
            ...
            filterChain.doFilter(request, response);
        }
    };
}

这就是全部，不需要任何注册。参见什么是OncePerRequestFilter?

过滤器主要用于日志文件中。它根据您在项目中使用的记录器而有所不同。

让我解释一下log4j2:

<Filters>
    <!-- It prevents an error -->
    <ThresholdFilter level="error" onMatch="DENY" onMismatch="NEUTRAL"/>

    <!-- It prevents debug -->
    <ThresholdFilter level="debug" onMatch="DENY" onMismatch="NEUTRAL" />

    <!-- It allows all levels except debug/trace -->
    <ThresholdFilter level="info" onMatch="ACCEPT" onMismatch="DENY" />
</Filters>

过滤器用于限制数据，我使用阈值过滤器进一步限制流中的数据级别。我提到了可以限制的水平。

请参见“log4j2 - Log4J Levels”的级别顺序:ALL > TRACE > DEBUG > INFO > WARN > ERROR > FATAL > OFF