Random Number Generation and Formatting in Thymeleaf

HowieHz

2025-02-20

🌍English

All examples presented in this article have been tested on Thymeleaf 3.1 and are applicable to various Thymeleaf scenarios, such as generating random numbers in Halo CMS themes.

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Integers

Generate random integer in range [min, min+range)

${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*range+min),0,0)}

Generate random integer in range [min, max]

${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*(max-min+1)+min),0,0)}

Click to view examples

A <p> tag displaying an integer between [1, 6) ([1, 5]). Possible results: 1, 2, 3, 4, 5.

Method 1

<p
  th:with="range=5,min=1"
  th:text="${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*range+min),0,0)}"
></p>

Method 2

<p
  th:with="max=5,min=1"
  th:text="${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*(max-min+1)+min),0,0)}"
></p>

Using as List Index

No need for #numbers.formatDecimal when used as list index. Replace my_list with your actual list variable:

Click to view example

<p
  th:with="randomIndex=${T(java.lang.Math).floor(T(java.lang.Math).random()*#lists.size(my_list))}"
  th:text="${my_list[randomIndex]}"
></p>

Formatting Control

Formatted random integer in [min, min+range)
Format: Integer part ≥ integerDigits (padded with leading zeros), decimal part fixed to decimalDigits.

${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*range+min),integerDigits,decimalDigits)}

Formatted random integer in [min, max]
Same formatting rules as above:

${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*(max-min+1)+min),integerDigits,decimalDigits)}

Click to view examples

A <p> tag displaying an integer between [0, 5) ([0, 4]). Possible results: 000.00, 001.00, 002.00, etc.

Method 1

<p 
  th:with="range=5,min=0,integerDigits=3,decimalDigits=2"
  th:text="${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*range+min),integerDigits,decimalDigits)}"
></p>

Method 2

<p 
  th:with="max=4,min=0,integerDigits=3,decimalDigits=2"
  th:text="${#numbers.formatDecimal(T(java.lang.Math).floor(T(java.lang.Math).random()*(max-min+1)+min),integerDigits,decimalDigits)}"
></p>

Decimals/Floats

Generate random float in [min, max)

${T(java.lang.Math).random()*(max-min)+min}

Click to view example

A <p> tag displaying a float between [0.5, 1.8). Possible results: 1.46833041859471749, 0.5578399752996518908, etc.

<p
  th:with="max=1.8,min=0.5"
  th:text="${T(java.lang.Math).random()*(max-min)+min}"
></p>

Formatting Control

Formatted random float in [min, max)
Format: Integer part ≥ integerDigits (padded with leading zeros), decimal part fixed to decimalDigits.

${#numbers.formatDecimal(T(java.lang.Math).random()*(max-min)+min,integerDigits,decimalDigits)}

Click to view example

A <p> tag displaying a float between [0.5, 150.8). Possible results: 00.83, 70.22, 150.23, etc.

<p
  th:with="max=150.8,min=0.5,integerDigits=2,decimalDigits=2"
  th:text="${#numbers.formatDecimal(T(java.lang.Math).random()*(max-min)+min,integerDigits,decimalDigits)}"
></p>

Project Status

As of publication (February 20, 2025), the Thymeleaf random number feature request remains open with no updates:
Random integer in #numbers · Issue #787 · thymeleaf/thymeleaf