Load Testing & Performance Benchmarking (JMeter & k6) · 课时

处理动态值（关联）

学习如何使用正则表达式提取器从服务器响应中提取并复用动态值

处理动态值（关联） 是 CoddyKit 上的免费 Load Testing & Performance Benchmarking (JMeter & k6) 课时。这是第 2 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Load Testing & Performance Benchmarking (JMeter & k6) 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Load Testing & Performance Benchmarking (JMeter & k6) 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Dynamic Values Explained

When you interact with a web application, many values in the server's responses aren't static. These are called dynamic values.

They change with each user, session, or even each request. Think of them like temporary keys the server gives you.

Session IDs
Authentication Tokens
CSRF Tokens

Why Correlation is Essential

If your performance test simply records and replays requests, it often fails. Why?

Because the recorded requests contain old, invalid dynamic values. The server rejects them, thinking you're not a legitimate user or session.

Correlation is the process of extracting these dynamic values from one response and reusing them in subsequent requests.

Meet the Regex Extractor

JMeter provides a powerful tool to handle dynamic values: the Regular Expression Extractor.

This Post-Processor component allows you to define a pattern (a regular expression) to search within a server's response and capture specific data.

It's like telling JMeter: "Find this pattern, and grab whatever is inside these brackets!"

How Extraction Works

Here's the basic flow for using a Regular Expression Extractor:

Send Request: Your JMeter sampler sends a request to the server.
Receive Response: The server sends back a response, which contains the dynamic value.
Extract Value: The Regular Expression Extractor scans the response for your defined pattern.
Store Value: It captures the dynamic data and stores it in a JMeter variable.
Reuse Value: You then use this variable in subsequent requests.

Regex Basics for Extraction

A Regular Expression (Regex) is a sequence of characters that defines a search pattern. For extraction, you'll often use:

. (dot): Matches any single character.
* (asterisk): Matches zero or more occurrences of the preceding character.
? (question mark): Makes the preceding quantifier (like *) non-greedy, matching the smallest possible string.
() (parentheses): Used to capture the part of the string you want to extract.

Try running this simple JavaScript example to see regex in action:

function extractId(text) {
  // Regex to find "id=" followed by one or more digits
  // and capture the digits.
  const regex = /id=(\d+)/;
  const match = text.match(regex);
  return match ? match[1] : null;
}

console.log("Extracted ID:", extractId("user?id=123&name=test"));
console.log("Extracted ID:", extractId("product?id=456"));
console.log("Extracted ID:", extractId("no_id_here"));

Adding the Extractor

In JMeter, the Regular Expression Extractor is a Post-Processor. This means it runs after a sampler (request) completes but before the results are recorded.

To add it:

Right-click on the HTTP Request (or other sampler) that receives the dynamic value.
Go to Add > Post-Processors > Regular Expression Extractor.

It will become a child of that specific request.

Extractor Configuration

The Regular Expression Extractor has several key fields:

Reference Name: The name of the JMeter variable to store the extracted value (e.g., sessionId).
Regular Expression: The actual regex pattern to match (e.g., name="sessionId" value="(.+?)").
Template: How to construct the value. Use $1$ for the first captured group, $2$ for the second, etc.
Match No.: If multiple matches, which one to use? 0 for random, 1 for first, -1 for all (creates multiple variables).
Default Value: A value to assign if the regex doesn't find a match.

Using the Extracted Variable

Once the Regular Expression Extractor stores a value in a variable (e.g., sessionId), you can use it in any subsequent JMeter sampler or component.

To reference the variable, use the syntax ${ReferenceName}.

For example, if you extracted a session ID into sessionId, you might use ${sessionId} in the body or URL path of a follow-up request.

A Correlation Scenario

Consider a login sequence:

Request 1 (Login): Sends username/password.
Response 1: Contains a CSRF_Token in a hidden field.
Regex Extractor: Extracts CSRF_Token from Response 1 and stores it in ${csrfToken}.
Request 2 (Submit Form): Uses ${csrfToken} in its request body or URL parameters.

This ensures your test script behaves like a real user, passing the dynamic token.

Test Your Regex Knowledge

Imagine a server response contains the following HTML snippet:

<input type="hidden" name="token" value="abc123xyz456" />

You want to extract the value abc123xyz456 into a JMeter variable named authToken.

Which Regular Expression and Template combination should you use in the Regular Expression Extractor?

Recap: Mastering Correlation

Great job! You've learned the critical skill of correlation in JMeter.

Dynamic values require special handling to prevent test failures.
The Regular Expression Extractor is JMeter's primary tool for this.
You define a regex pattern to capture specific data from server responses.
Extracted values are stored in JMeter variables for reuse in subsequent requests.

This technique makes your performance tests robust and realistic. Next, we'll explore more JMeter functions and variables for even greater script flexibility!

常见问题解答

「处理动态值（关联）」课时是免费的吗？

是的 — 「处理动态值（关联）」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Load Testing & Performance Benchmarking (JMeter & k6) 课程的其余内容，请升级到 CoddyKit PRO。 Load Testing & Performance Benchmarking (JMeter & k6) 课程共包含 4 节课。

「处理动态值（关联）」这节课中我会学到什么？

学习如何使用正则表达式提取器从服务器响应中提取并复用动态值你通过在浏览器中直接运行的动手代码来练习 Load Testing & Performance Benchmarking (JMeter & k6)，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Load Testing & Performance Benchmarking (JMeter & k6) 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Load Testing & Performance Benchmarking (JMeter & k6) 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 2 节课，共 4 节。

「处理动态值（关联）」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Load Testing & Performance Benchmarking (JMeter & k6) 课中编写并运行代码吗？

能。每节 Load Testing & Performance Benchmarking (JMeter & k6) 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

← 返回 Load Testing & Performance Benchmarking (JMeter & k6)