Blue Coat Systems Time Clock Proxy SG Manuale Utente

Chapter 6: Definition Reference

265

define url_rewrite

Defines rules for rewriting URLs embedded in tags within HTML, CSS, JavaScript or ASX documents. 
This transformer takes effect only if it is also invoked by a 

transform

 action in a 

define action

 

definition block, and that block is in turn called from an 

action( )

 property.

For each url found within an HTTP response, a 

url_rewrite

 transformer first converts the URL into 

absolute form, then finds the first 

subst_embedded

 or 

subst_prefix

 statement whose 

 matches the URL being considered. If such a match is found, then that 

substring is replaced by the 

. 

Matching is case-sensitive by default; use the optional 

caseless

 keyword for case-insensitive 

matching. All 

subst_embedded

 statements after the first occurrence of the caseless keyword use 

case-insensitive string matching.

Multiple URL prefix substitutions can be made in a single 

define url_rewrite

 definition block. This 

type of transformation is often used in conjunction with the request URL form of the 

rewrite( )

 

action in a server portal application. 

To find URLs within an HTTP response, the ProxySG looks for 

Location:

, 

Content-Location:

, and 

Refresh:

 headers, and parses HTML, JavaScript, CSS, and ASX files. The ProxySG does not search for, 

nor rewrite relative URLs embedded within Javascript.

Pages served over an HTTPS tunneled connection are encrypted, so URLs embedded within 
them cannot be rewritten.

Transformed content is not cached (although the original object may be), in contrast with 
content that has been sent to a virus scanning server. This means any transformer can be safely 
triggered based on any condition, including client identity and time of day.

Replaces: 

transform url_rewrite

define url_rewrite transformer_id

[caseless]

subst_embedded "client_url_substring" "server_url_substring"

subst_prefix "client_url_substring" "server_url_substring"

...

end

where:

•

—A user-defined identifier for a transformer definition block. Used to invoke the 

transformer using the 

transform

 action in a 

define action

 definition block.

•

subst_embedded

—Matches 

 anywhere in the URL.

•

subst_prefix

—Matches 

 as a prefix of the URL.

•

—A string that will replace 

server_url_substring 

when that string is 

matched for a URL in the retrieved document. The portion of the URL that is not substituted is 
unchanged.