JMeter-使用$ {}或vars.get()获得变量值之间的区别是什么 [英] JMeter-what is difference between use ${} or vars.get() to get value of variable

问题描述

今天，当我调试JMeter脚本时，发现了一个使我感到困惑的问题.

Today when I was debugging my JMeter script, I found a problem that confused me a lot.

1. CSV数据配置元素:在CSV中，我将变量userId设置为1001200

1. CSV Data Config element: in CSV, I set variable userId to 1001200

1. 然后在下面运行脚本，并在使用${userId}和vars.get("userId")时获得不同的"userId"值.我认为它们应该具有相同的值，但事实并非如此.运行vars.put("userId", "-111")之后，${userId}和vars.get("userId")获得不同的值:

1. Then run script below, and get different value of "userId" when using ${userId} and vars.get("userId"). I think they should be same value, but it seems not. After run vars.put("userId", "-111"), ${userId} and vars.get("userId") get different values:

因此，即使${}和vars.get()的变量相同，似乎也有一些区别，有人知道原因吗?

so it seems ${} and vars.get() have some difference even though their variable is same, does anyone know the reason?

谢谢.

推荐答案

@ user7294900提供的答案是指选中缓存编译脚本选项的情况.但是，即使未选中它，您的脚本也将在执行前解析定义为${varName} 的变量，而在执行期间解析vars.get("varName")的变量.

Answer provided by @user7294900 refers to the case when Cache compiled script option is checked. But even if it's not checked, your script will resolve variables defined as ${varName} before execution, while vars.get("varName") is resolved during execution.

在JMeter即将运行任何元素(采样器，预处理器或后处理器)之前，它将占用(每个)文本字段，并将由${...}标识的任何变量，函数或内联代码解析为可用的值在评估时.因此语法${...}将变量转换为常量字符串，并且您的代码(对于Groovy或任何其他执行引擎)将如下所示:

Before JMeter is about to run any element (sampler, pre- or post-processor), it will take (every) text field and will resolve any variables, functions or inline code, identified by ${...} to their values available at the time of the evaluation. Thus syntax ${...} converts variable into a constant string and your code (for Groovy or any other execution engine) will look like this:

    log.info("***" + "1001200" + "***");
    log.info("***" + vars.get("userId") + "***");
    vars.put("userId", "-111");
    log.info("***" + "1001200" + "***");
    log.info("***" + vars.get("userId") + "***");

因此，无论您在执行过程中如何更改变量，它都不会更改，因为它不再是变量.但是vars.get("userId")另一方面是函数调用，并且每次都会检查变量值.

Thus no matter how you change variable during execution, it won't change since it's no longer a variable. But vars.get("userId") on the other hand, is a function call and will check variable value every single time.

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