Using ExtractVariable policy to extract HTTP header and printing on console using JavaScript

[ramgkrishnancer]

Hi,

I'm very new to APIGEE and have been going through 4MV4D by Anil to try out some scenarios. My scenario is very simple.

I have created a "Reverse Proxy" and mapped it to httpbin.org/get as target. I'm trying to use ExtractVariable policy to extract the "Content-Encoding" HTTP header and use a JavaScript policy to print to the console.

Here's my code from "ExtractVariable" policy:

....

<Header name="Content-Encoding">  
    <Pattern ignoreCase="true">CE {response.header.Content-Encoding}</Pattern>  
</Header>
<Source clearPayload="false">response</Source>

....

This is what I'm using to print to the console using JavaScript

print(context.getVariable("CE"));

Both the "ExtractVariable" policy and JavaScript policy is applied to the response path of the Pre-Flow.

The proxy executes successfully and I get a 200 OK and a successful response back in the browser, however, I'm seeing null being printed on the console.

What am I missing here? Can anyone please suggest?

[nagashree_b]

@Ram GKrishnan

Firstly, httpbin.org/get doesn't return Content-Encoding Header

Secondly you are trying to match a pattern like "CE 123", and you are trying to assign it to flow variable response.header.Content-Encoding. The value of response.header.Content-Encoding will be 123. You haven't defined a variable called CE, but you are trying to print the value of variable CE.

Below is a code snippet for Content-type header, where I am trying to match a pattern application/xxx

<Header name="Content-Type">
<Pattern ignoreCase="true">application/{matchedValue}</Pattern>
</Header>
<Source clearPayload="false">response</Source>

matchedValue is the variable that will contain the value or you could use

<Pattern ignoreCase="true">{matchedValue}</Pattern> to read the complete value into the variable.

The javascript can print the same with the below line of code

print(context.getVariable("matchedValue"));

Attaching the proxy code if that helps you.

no-target-rev1-2019-02-28-1.zip

trace-1551314809427.txt