Add Resource Headers and allow EL Expressions only on css files

Actually, we have two methods in ResourceImpl with TODO'S:

ResourceImpl.getResponseHeaders()
ResourceImpl.userAgentNeedsUpdate()

This two were let without implementation, because it was not clear how it should behave. If EL Expressions were allowed, to allow add cache headers the value returned must be

"application scope", but nothing on the spec says something about that.

This issue should be solved before start TOMAHAWK-1472 Add Support for new Resource API in tomahawk 2.0 module, because we need to define if a ResourceHandlerWrapper is required to provide some features and how it should behave.

There was some discussion on jsr-314-open@jcp.org around this two topic under the subject:

[jsr-314-open] Evaluating EL in resource files

Fortunately, it seems some conclusion arise from this discussion, but there are not details about it, so we are forced to make a black box test on the latest release (2.0.1) to

know what happened and decide what should we do on our side.

Doing some test with ri and firebug, these were the results:

RI
GET teststyle.css.jsf
Header Request:

Host localhost:8080
User-Agent Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)
Accept text/css,/;q=0.1
Accept-Language es-es,es;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost:8080/test-webapp/resourceHeaders.jsf
Cookie JSESSIONID=1pkha2z8zhgvu
If-Modified-Since Fri, 11 Dec 2009 21:34:07 GMT
If-None-Match W/"153-1260567247625"

Header Response:

X-Powered-By JSF/2.0
Content-Type text/css
Expires Fri, 11 Dec 2009 22:00:33 GMT
Etag W/"153-1260567247625"
Last-Modified Fri, 11 Dec 2009 21:34:07 GMT
Content-Length 121
Server Jetty(6.1.16)

RI
GET testjs.js.jsf
Header Request:

Host localhost:8080
User-Agent Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)
Accept /
Accept-Language es-es,es;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost:8080/test-webapp/resourceHeaders.jsf
Cookie JSESSIONID=1pkha2z8zhgvu
If-Modified-Since Fri, 11 Dec 2009 21:34:13 GMT
If-None-Match W/"102-1260567253406"

Header Response:

X-Powered-By JSF/2.0
Expires Fri, 11 Dec 2009 22:00:33 GMT
Content-Type application/x-javascript
Etag W/"102-1260567253406"
Last-Modified Fri, 11 Dec 2009 21:34:13 GMT
Content-Length 102
Server Jetty(6.1.16)

RI
GET button.gif.jsf
Header Request:

Host localhost:8080
User-Agent Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)
Accept image/png,image/;q=0.8,/*;q=0.5
Accept-Language es-es,es;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Referer http://localhost:8080/test-webapp/resourceHeaders.jsf
Cookie JSESSIONID=1pkha2z8zhgvu
If-Modified-Since Wed, 02 Dec 2009 04:52:45 GMT
If-None-Match W/"61-1259729565078"

Header Response:

X-Powered-By JSF/2.0
Content-Type image/gif
Expires Fri, 11 Dec 2009 22:07:47 GMT
Etag W/"61-1259729565078"
Last-Modified Wed, 02 Dec 2009 04:52:45 GMT
Content-Length 61
Server Jetty(6.1.16)

MYFACES

GET testjs.js.jsf
Header Request:

Host localhost:8080
User-Agent Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)
Accept text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
Accept-Language es-es,es;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Cookie JSESSIONID=1pkha2z8zhgvu

Header Response:

Content-Type application/x-javascript
Content-Length 72
Server Jetty(6.1.16)

Also, a 304 Not Modified response was returned by the server for all resources.

It was tested too if EL expressions are allowed on javascript or css files, but now it is only allowed on css files.

The problem with ProjectStage in jsf javascript api was solved adding a param called "stage" on the rendered javascript url. If we are on Production stage, no param is written,

but if we are on other stage, the javascript code must extract it in some way from its base url.

Since cache headers are present when request for resources, EL Expressions has application scope.

Note all three component libraries: Tobago, Trinidad and Tomahawk add cache headers, so we need to review what we do on all three:

Tomahawk:

MyFacesResourceLoader read and set the following headers:

If-Modified-Since (read)
Last-Modified (set)
Expires (set one week later)
Cache-Control (set max-age=43200 or 12 hours)

It also has an algorithm to correct contentType.

StreamingResourceLoader set the following headers:

pragma (set no-cache)
Cache-control (no-cache, must-revalidate)

CAPTCHARenderer does not set renderers.

In theory, for jsf 2.0 we can replace MyfacesResourceLoader with the default impl and use a ResourceHandlerWrapper for StreamingResourceLoader and CAPTCHARenderer instead.

Trinidad:

ResourceServlet has a method _setHeaders that set the following:

Last-Modified (Depends if is file or jar)
Cache-Control (set Public)
Expires (set to one year later)

Tobago:

When no cache is required it sets:

response.setHeader("Cache-Control", "no-cache,no-store,max-age=0,must-revalidate");
response.setHeader("Pragma", "no-cache");
response.setDateHeader("Expires", 0);
response.setDateHeader("max-age", 0);

Otherwise on ResourceServlet

response.setHeader("Cache-Control", "max-age=" + expires);
response.setDateHeader("Expires", new Date().getTime() + (expires * 1000));

We have to keep into account css files have application scope for define cache headers.

That's all info required and pointers to code we can use for add cache headers on myfaces.