JMeter - Changing a Cookie's Value during a Test? - cookies

Question

I have created a test plan in JMeter *(Version 2.13). I was able to add a Cookie Manager to the plan and have my cookies preserved between HTTP Requests, which works just fine.
What I'm trying to do now is, if possible, preserve one Cookie from the start (*Called "JSESSIONID") and then have another Cookie (*let's call it "MYID") which can be modified during the test.
My 1st try at this was like the following:
+Thread Group
-HTTP Request Defaults
-HTTP Cookie Manager
+HTTP Request - Goto HomePage
-HTTP Cookie Manager - Set MYID="server_1"
+HTTP Request - Load Login Page
-HTTP Cookie Manager - Set MYID="server_2"
....and so on for about 3 more HTTP Requests....
But, doing it this way only kept the original Cookies which were captured by the initial Cookie Manager which was set right under the Thread Group element.
Apache's site warns that:
"If there is more than one Cookie Manager in the scope of a Sampler, there is currently no way to specify which one is to be used. Also, a cookie stored in one cookie manager is not available to any other manager, so use multiple Cookie Managers with care."
Another test I did, that was similar to the first except I added a User Defined Variables element to the start of the test which had a variable for the MYID Cookie set to one server, and then about 2 or 3 HTTP Requests down I had a second User Defined Variables element, this time setting the variable to another server. But, after reading a bit more on the User Variables, JMeter only reads User Defined Variables ONCE, at the beginning of the test. So the variable I set last would remain as whatever I set it to in the 2nd User Defined Variables section. So that way won't work to change the Cookie value during the test...
I also, read this from ApacheJMeter's site, here Using Variables to Parametrize Tests, which seems closest to what I am trying to achieve. But, from their example it seems as though it's for modifying variables before the test starts, like for example setting a variable from the command line...
Summary:
To sum things up, what I am trying to achieve is to send my HTTP Requests with 2 Cookies:
1. JSESSIONID
2. MYID
Where JSESSIONID will remain the same from the very start, and MYID which I want to change it's value during test *(multiple times if posible).
Let me know if that does not make sense and I will try and explain further.
Any thoughts or suggestions would be greatly appreciated!
Thanks in Advance,
Matt

Answer 1

You can use Beanshell scripting for cookies manipulation as:
Add a Beanshell PreProcessor to your HTTP Request
Put the following code into the PreProcessor's "Script" area:
import org.apache.jmeter.protocol.http.control.Cookie;
import org.apache.jmeter.protocol.http.control.CookieManager;
CookieManager manager = sampler.getCookieManager();
for (int i = 0; i < manager.getCookieCount(); i++) {
Cookie cookie = manager.get(i);
if (cookie.getName().equals("MYID")) {
cookie.setValue(vars.get("foo"));
manager.remove(i);
manager.add(cookie);
break;
}
}
Above code will substitute "MYID" cookie value with "foo" JMeter Variable value via direct calls to CookieManager class (see API documentation for all possible methods and fields)
Check out How to use BeanShell: JMeter's favorite built-in component guide for advanced information on Beanshell scripting in Apache JMeter.