CacheFilter

CacheFilter is a Java Servlet filter that allows you to enable browser caching for requested resources.

Filter parameters

Option	Required	Default	Since	Description
expiration	Yes	--	2.2.0	Cache directive to set an expiration time, in seconds, relative to the current date. Used for both Cache-Control and Expires HTTP headers.
private	No	false	2.0.0	Cache directive to control where the response may be cached. false indicates that the response MAY be cached by any cache. true indicates that the response is intended for a single user and MUST NOT be cached by a shared cache, a private (non-shared) cache MAY cache the response.
must-revalidate	No	false	2.2.0	Cache directive to define whether conditional requests(1) are required or not for stale responses. When the must-revalidate directive is present in a response received by a cache, that cache MUST NOT use the entry after it becomes stale to respond to a subsequent request without first revalidating it with the origin server.
vary	No	--	2.3.0	Cache directive to instruct proxies to cache different versions of the same resource based on specific request-header fields. Some possible Vary header values include: Accept-Encoding instructs proxies to cache two versions of a compressible resource: one compressed, and one uncompressed. Accept-Language instructs proxies to cache different versions of a resource based on the language of a given request. Accept instructs proxies to cache different versions of a resource based on the response format of a given request (e.g. Accept: application/xml or Accept: application/json). Warn: if your server does vary responses but does not indicate so via the Vary header it may result in cache corruption: Vary Header for RESTful Applications.

⁽¹⁾ If a component is already in the browser's cache and is being re-requested, the browser will pass the Last-Modified date in the request header. This is called a conditional GET request and if the component has not been modified, the server will return a 304 Not Modified response.

Sample configuration

Declare the filter in your web descriptor file web.xml:

<filter>
    <filter-name>imagesCache</filter-name>
    <filter-class>com.samaxes.filter.CacheFilter</filter-class>
    <init-param>
        <param-name>expiration</param-name>
        <param-value>2592000</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>cssCache</filter-name>
    <filter-class>com.samaxes.filter.CacheFilter</filter-class>
    <init-param>
        <param-name>expiration</param-name>
        <param-value>604800</param-value>
    </init-param>
    <init-param>
        <param-name>vary</param-name>
        <param-value>Accept-Encoding</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>jsCache</filter-name>
    <filter-class>com.samaxes.filter.CacheFilter</filter-class>
    <init-param>
        <param-name>expiration</param-name>
        <param-value>216000</param-value>
    </init-param>
    <init-param>
        <param-name>private</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>

Map the filter to serve your static resources:

<filter-mapping>
    <filter-name>imagesCache</filter-name>
    <url-pattern>/img/*</url-pattern>
</filter-mapping>

<filter-mapping>
    <filter-name>cssCache</filter-name>
    <url-pattern>*.css</url-pattern>
</filter-mapping>

<filter-mapping>
    <filter-name>jsCache</filter-name>
    <url-pattern>*.js</url-pattern>
</filter-mapping>