Sentinel Web Servlet Filter

Sentinel provides Servlet filter integration to enable flow control for web requests. Add the following dependency in pom.xml (if you are using Maven):

<dependency>
    <groupId>com.alibaba.csp</groupId>
    <artifactId>sentinel-web-servlet</artifactId>
    <version>x.y.z</version>
</dependency>

To use the filter, you can simply configure your web.xml with:

<filter>
	<filter-name>SentinelCommonFilter</filter-name>
	<filter-class>com.alibaba.csp.sentinel.adapter.servlet.CommonFilter</filter-class>
</filter>

<filter-mapping>
	<filter-name>SentinelCommonFilter</filter-name>
	<url-pattern>/*</url-pattern>
</filter-mapping>

For Spring web applications you can configure with Spring bean:

@Configuration
public class FilterConfig {

    @Bean
    public FilterRegistrationBean sentinelFilterRegistration() {
        FilterRegistrationBean<Filter> registration = new FilterRegistrationBean<>();
        registration.setFilter(new CommonFilter());
        registration.addUrlPatterns("/*");
        registration.setName("sentinelFilter");
        registration.setOrder(1);

        return registration;
    }
}

When a request is blocked, Sentinel servlet filter will give a default page indicating the request blocked. If customized block page is set (via WebServletConfig.setBlockPage(blockPage) method), the filter will redirect the request to provided URL. You can also implement your own block handler (the UrlBlockHandler interface) and register to WebCallbackManager.

The UrlCleaner interface is designed for clean and unify the URL resource. For REST APIs, you have to clean the URL resource (e.g. /foo/1 and /foo/2 -> /foo/:id), or the amount of context and resources will exceed the threshold. The UrlCleaner interface can also exclude unused URLs(e.g. /exclude/1 -> /exclude/:id -> ""). The URLs will be filtered and not be resource in this way.

RequestOriginParser interface is useful for extracting request origin (e.g. IP or appName from HTTP Header) from HTTP request. You can implement your own RequestOriginParser and register to WebCallbackManager.