Sentinel/sentinel-adapter/sentinel-web-servlet/README.md

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# 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):
```xml
<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:
```xml
<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>
```
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.
`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`.