# Servlet Filter

Installing the <code class="expression">space.vars.X\_Agent\_Name\_Single</code> as a Servlet filter in a Java Application Server *(such as Jetty, WebSphere, JBoss etc.)*, is a common approach. In this scenario, the <code class="expression">space.vars.X\_Agent\_Name\_Single</code> is acting like a Servlet Filter sees all requests coming in and has the ability to modify the request before it reaches the web application. Similarly, is also sees every response coming back from the web application and it has the ability to modify these responses on the fly.

<figure><img src="/files/Hmmd5yTQK82RKqJxeY7S" alt=""><figcaption><p>Graph</p></figcaption></figure>

Use cases for this approach mostly centre around making temporary changes to an existing web application, out of band of release cycles, or when the web application is third party and not able to be modified.

Examples of such temporary changes include:

* Adding security such as CSRF or SQL Injection protection
* Frequently changed compliance rules that can be required on short notice


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