如何在JMeter中基于前一个Sampler响应值控制采样器执行？

Hey there! I’ve tackled this exact conditional flow in JMeter before, so let’s break down the steps to make this work for you:

1. 先从响应里提取要判断的属性值 #

First up, you need to pull the target property from your first Sampler’s response. The JSON Extractor is perfect for this:

• Right-click your first Sampler → Add → Post Processors → JSON Extractor
• In the JSON Path Expression field, enter the path to your target property. For example, if your response has an array property like "tags": [], use $.tags
• Give it a Reference Name (something memorable like targetArrayProperty) so you can reference it later

2. 用If Controller实现分支判断 #

Next, add an If Controller to handle the "IF" case:

• Right-click your Test Plan/Thread Group → Add → Logic Controller → If Controller
• In the Condition box, paste this JEXL3 expression to check if the extracted value is exactly []:

  ${__jexl3("${targetArrayProperty}" == "[]",)}
  

  • JEXL3 is great for precise string comparisons here—make sure the quoted [] matches exactly what your response returns (no extra spaces!)

3. 添加IF分支的请求 #

Drag the Sampler you want to run only when the property is [] into this If Controller. It’ll only execute when the condition is true.

4. 设置ELSE分支的请求 #

For the "ELSE" case, add another If Controller with the inverse condition:

• Create a second If Controller, and use this condition:

  ${__jexl3("${targetArrayProperty}" != "[]",)}
  

• Drop your alternate Sampler into this second If Controller—it’ll run whenever the first condition fails.

Quick Notes to Avoid Headaches: #

• Always verify your extracted variable works first! Use the View Results Tree listener to check if ${targetArrayProperty} is correctly pulling [] (or the non-empty value) from the response
• If your empty array might have whitespace (like [ ]), adjust the condition to match that exact string
• If you’re dealing with a property that could be null instead of [], you’ll need to tweak the condition to account for that (e.g., combine with ${__isBlank(${targetArrayProperty},)})

内容的提问来源于stack exchange，提问作者Siddish