Citrix Systems 9.2 Manual De Usuario

If a request or response that you configure in an HTTP callout 

(-

fullReqExpr 

or -

resultExpr

) contains the expression SYS.

HTTP_CALLOUT

, the callout can recursively generate additional callouts. You 

should avoid this. Also, be sure that the HTTP callout configuration is complete. 
For example, if the callout contains a rule but not a server where the callout is to 
be sent, it can return a value of “undefined.” 

1.

In the left navigation pane, expand AppExpert, and then click HTTP 
Callouts.

Expression-based 
request to send to the 
server 
(fullReqExpr) 

Exact HTTP request that the NetScaler is to send as an advanced 
expression to 8191 characters. 

If you specify this parameter, you must omit the httpMethod, 
hostExpr

, urlStemExpr, headers, and parameters 

arguments. 

The request expression is constrained by the feature where the 
callout is used. For example, an HTTP.RES expression cannot be 
used in a request-time policy bank or in a TCP content switching 
policy bank. 

The NetScaler does not check the validity of this request. You 
must manually validate the request. 

Return type

(returnType)

Type of data that the target application returns in the response to 
the callout. Valid values:

• TEXT: Treat the returned value as a text string. 
• NUM: Treat the returned value as a number.
• BOOL: Treat the returned value as a Boolean value. 
Note: You cannot change the return type after it is set.

Expression to extract 
data from the 
response

(resultExpr)

Advanced expression that extracts HTTP.RES objects from the 
response to the HTTP callout. The maximum length is 8191.

The operations in this expression must match the return type. For 
example, if you configure a return type of text, the result 
expression must be a text-based expression. If the return type is 
num

, the result expression (resultExpr) must return a 

numeric value similar to the following:

"http.res.body(10000).length"

Note: In some cases, if you set a return type of TEXT and the 
result sent from the server exceeds 16 KB, the result expression 
can return NULL. For example, this can happen when the result is 
a concatenated string that exceeds 16 KB.