1. Start jmeter, add a thread group, right-click to add a configuration element - counter
2. Counter page
The initial value, increment, and reference name are required, and the others are optional
Starting value (starting value): Given the starting value and initial value of the counter, the value will be assigned to the counter at the first iteration
Increment: The value to add to the counter after each iteration
Maximum: The maximum value of the counter. If it exceeds the maximum value, it will be reset to the initial value (Start). The default maximum value is Long.MAX_VALUE, 2^63-1 (if the pressure test continues, it is recommended not to set it max)
Number format (Number format): optional format, such as 000, formatted as 001, 002; the default format is Long.toString(), but in the default format, it can still be used as a number
Reference Name: used to control the reference to the value in other elements, in the form: reference_name
Track Counter Independently for each User (Track Counter Independently for each User): global counter, if not checked, it is global, for example, user #1 obtains a value of 1, and user #2 obtains a value of 1;
If checked, that is, independent, each user has its own value: for example, user #1 gets a value of 1, and user #2 gets a value of 2.
Reset counter on each Thread Group Iteration (Reset counter on each Thread Group Iteration): optional, only available when the independent tracking counter for each user is checked;
If checked, the value of the counter will be reset every time the thread group iterates, which is useful when the thread group is in a loop controller.
3. References in message body data
Reference format: ${orderNumber}
It can be seen in the actual request that the counter generates the value we need
