Gatling集成Karate时Feeder数据无法传入Feature，取值显示Undefined的问题求助

I’ve run into this exact frustrating issue before—when your feeder data just refuses to make its way to the Karate feature file! Let’s break down the likely causes and actionable fixes step by step.

First: Confirm Your Gatling Session Has the Data #

First things first—let’s rule out whether the feeder is even putting data into the Gatling session. Your Simulation already includes a println(session) line, so check the console output when you run the test. You should see a session entry like this:

Session(Scenario name,1,Map(uri -> https://dev-url.com, token -> your-actual-token, userId -> 12345), ...)

If the uri, token, or userId keys are missing from this output, the problem lies with your feeder, not the Karate integration:

• Double-check that runEnv is properly assigned (e.g., val runEnv = "dev" somewhere in your Simulation). A missing runEnv would create an invalid uri, but it should still appear in the session.
• Verify that getApiAuthToken returns valid values for getToken and getUserID. Test with hardcoded values temporarily to isolate the issue:

  private val feeder = Iterator.continually(Map(
    "uri" -> "https://test-url.com",
    "token" -> "test-token-123",
    "userId" -> "999"
  ))
  

  If this hardcoded data shows up in the session, your getApiAuthToken method is likely returning null or has an async/execution issue.

If Session Has Data, Fix Karate’s Variable Access #

If the session contains the data but Karate still shows undefined, let’s adjust how variables are passed to the feature file:

Option 1: Explicitly Pass Variables to Karate #

Instead of relying on the __gatling prefix, explicitly pass session variables to the Karate feature using .set()—this is often more reliable:

val scn: ScenarioBuilder = scenario("Scenario name")
  .feed(feeder)
  .exec(session => {
    println(session)
    session
  })
  .exec(karateFeature("classpath:specs/api.feature")
    .set("uri", "${uri}")
    .set("token", "${token}")
    .set("userId", "${userId}")
  )

Then update your Feature file to use the variable names directly (no __gatling prefix):

Feature: Scenario name 
Background: 
* url uri 
* header Authentication = 'Token ' + token 

Scenario: Get User Details 
Given path 'users', userId 
When method get 
Then status 200 
And print response

Option 2: Fix the __gatling Syntax #

If you prefer using the __gatling prefix, some Karate versions require bracket notation instead of dot notation to access session variables. Try modifying your Feature file:

Background: 
* url __gatling['uri'] 
* header Authentication = 'Token ' + __gatling['token'] 

Scenario: Get User Details 
Given path 'users', __gatling['userId']

Check Version Compatibility #

Make sure your Gatling and Karate versions play nice together:

• Karate 1.0.x works best with Gatling 3.7+
• Older Karate versions (<=0.9.6) have different __gatling variable behavior. Upgrading to a recent stable version often resolves these integration quirks.

Bonus: Clean Up Your Karate Protocol Definition #

Your current protocol has duplicate "/" entries, which might cause unexpected behavior (though not directly the undefined issue). Update it to target specific paths:

val protocol: KarateProtocol = karateProtocol( 
  "/users" -> Nil, 
  "/" -> pauseFor("get" -> 3, "post" -> 5) 
)

内容的提问来源于stack exchange，提问作者Taras Horuk