cache-headers-filter

Grails plugin which brings in a servlet filter for setting HTTP cache headers on HTTP responses.

Plugin implementation is based on cache-headers plugin. Difference is that a servlet filter can be applied on any request, not only on controller outputs like with cache-headers plugin.

Introduction

When first needed caching filter, it was surprise for me that finding one is pretty hard. There are many related options like cache-headers plugin, jawr (and corresponding grails plugin), asset pipeline etc. Jawr and asset pipeline do lot more than caching, but they are doing so for resources known at compile or package time. On the other hand, cache-headers is applicable at runtime, but it can setup HTTP cache headers for controller outputs only.

I was in situation when I needed setting up caching headers at runtime, but not for controller outputs, but rather for requests that originated from a client which was requesting resources only (JavaScript and CSS files). And that leads me to implementing this plugin.

cache-headers-filter plugin can work along with cache-headers (in fact, cache-headers is very strong dependency of cache-headers-filter implementation), jawr and asset pipeline.

Installation

Add the plugin as runtime dependency under plugins section in your BuildConfig.groovy:

runtime ":cache-headers-filter:0.0.1"

Usage

As said before, cache-headers-filter relies heavily on cache-headers plugin. More specifically, cache-headers-filter expects and relies on presets configuration of cache-header plugin. For example, suppose that we have cache-headers presets configured this way in Config.groovy:

cache.headers.presets = [
  "noCache": false,  // do not cache
  "cache6Months": [shared: true, validFor: 1 * 60 * 60 * 24 * 30 * 6] // cache for 6 months
]

With this in place, cache-headers-filter configuration part can be specified, which might look something like this:

grails.plugins.cacheHeadersFilter.mappingList = [
    [
        cacheHeadersPreset: "noCache",
        type: "ant",
        pathList: [
            "/senchaWorkspace/build/production/**/*-classic-*.json",
            "/senchaWorkspace/build/production/**/*-modern-*.json",
            "/senchaWorkspace/build/production/**/bootstrap.js"
        ]
    ],
    [
        cacheHeadersPreset: "cache6Months",
        type: "ant",
        pathList: [
            "/senchaWorkspace/build/production/**/*.*"
        ]
    ]
]

To be able to use cache-headers-filter plugin, grails.plugins.cacheHeadersFilter.mappingList must be specified. mappingList is a list of maps, where each map consist of several keys:

cacheHeadersPreset - this is a name of a caching preset defined for cache-headers plugin. Name is used as a reference to the group of caching options to be set.
type - optional parameter which defines type of matcher and, implicitly, the syntax to be used in pathList config. Allowed values are ant and regex (or just re). Default is ant.
pathList - list of paths on which caching headers will be applied.

Note that ordering of mappingList elements is significant since first found match will be activated. Therefore, when creating mappingList configuration, start with most specific paths.

Other config options

grails.plugins.cacheHeadersFilter.enabled - boolean to enable or disable plugin. Default value is true.
grails.plugins.cacheHeadersFilter.filterMappingUrlPattern - String for defining filter mapping url pattern for this filter. Default value is /*.

Logging

To see log output of a plugin, turn on desired level of logging for a package org.grails.plugins.cacheheadersfilter:

debug "org.grails.plugins.cacheheadersfilter"

Version note

Although the plugin is currently at version 0.0.1, it is feature complete. It will go at version 1.0.0 after some passed time and production usage just to make sure there is no blockers present.